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Reading/Writing C64 disks on Apple // [message #358169] Fri, 08 December 2017 09:05 Go to next message
anthonypaulo is currently offline  anthonypaulo
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I read somewhere that it would be possible to r/w C64 disks on the Disk II if it were possible to change the speed of the drive. Is it that the Disk II is too slow? If not, then perhaps it would be possible to match the C64 disk speed by toggling the drive motor on and off to get the desired speed?
Reading/Writing C64 disks on Apple // [message #358173 is a reply to message #358169] Fri, 08 December 2017 10:04 Go to previous messageGo to next message
Antoine Vignau is currently offline  Antoine Vignau
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I think that the recording format is different. It can be done but with a dedicated disk controller.

Please correct me if I am wrong,
Antoine
Re: Reading/Writing C64 disks on Apple // [message #358174 is a reply to message #358169] Fri, 08 December 2017 10:06 Go to previous messageGo to next message
David Schmidt is currently offline  David Schmidt
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On 12/8/2017 9:05 AM, Anthony Ortiz wrote:
> I read somewhere that it would be possible to r/w C64 disks on the Disk II if it were possible to change the speed of the drive.

Where did you read that?
Re: Reading/Writing C64 disks on Apple // [message #358181 is a reply to message #358174] Fri, 08 December 2017 10:42 Go to previous messageGo to next message
anthonypaulo is currently offline  anthonypaulo
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It was alluded to by David Empson (if I’m reading him right) in an old thread called ‘Apple II <-> Commodore 64/128 disks?’ Way back in ‘97
Re: Reading/Writing C64 disks on Apple // [message #358182 is a reply to message #358181] Fri, 08 December 2017 11:04 Go to previous messageGo to next message
David Schmidt is currently offline  David Schmidt
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On 12/8/2017 10:42 AM, Anthony Ortiz wrote:
> It was alluded to by David Empson (if I’m reading him right) in an old thread called ‘Apple II <-> Commodore 64/128 disks?’ Way back in ‘97

Hmmm, that's not at all what David said then. Speed is the same on both
drives (300RPM). The encoding techniques are different (the various GCR
schemes, which David went through) all differ from Commodore's GCR
encoding scheme. The recording density does change in the Commodore's
case - as they get closer to the center of the spindle, they record less
information. That would require a change in rotational speed (such as
Apple did with their early 400/800KB 3.5" drives) or a change in bitcell
timing (such as Commodore did). As Antione points out, this isn't going
to happen with the standard Disk II controller. But by the time you
start using a programmable controller (such as the Catweasel as one
example) you already control all the aspects you need - bitcell timing,
encoding, all that. So given the right hardware and processing power,
you can read and write essentially everything there is. But the Apple
II with a Disk II controller doesn't have the right combination to read
or write CBM formats.
Re: Reading/Writing C64 disks on Apple // [message #358183 is a reply to message #358182] Fri, 08 December 2017 11:10 Go to previous messageGo to next message
anthonypaulo is currently offline  anthonypaulo
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That’s what I mean, a change in rotational speed is what’s needed; would it be possible to change the speed by toggling the motor on/off?
Re: Reading/Writing C64 disks on Apple // [message #358184 is a reply to message #358182] Fri, 08 December 2017 11:14 Go to previous messageGo to next message
anthonypaulo is currently offline  anthonypaulo
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Pardon my ignorance, but I thought encoding is up to the software and not hardware dependent.
Re: Reading/Writing C64 disks on Apple // [message #358185 is a reply to message #358183] Fri, 08 December 2017 11:15 Go to previous messageGo to next message
David Schmidt is currently offline  David Schmidt
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On 12/8/2017 11:10 AM, Anthony Ortiz wrote:
> That’s what I mean, a change in rotational speed is what’s needed; would it be possible to change the speed by toggling the motor on/off?

Even if you had the time to twiddle the motor on and off while timing
bits to shift out the write register (which you don't) and it could
become stable across different drive/motor manufacturers (which it
wouldn't) you still wouldn't have the ability to write arbitrary (i.e.
CBM) bit patterns using the Disk II controller.
Re: Reading/Writing C64 disks on Apple // [message #358186 is a reply to message #358184] Fri, 08 December 2017 11:22 Go to previous messageGo to next message
David Schmidt is currently offline  David Schmidt
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On 12/8/2017 11:14 AM, Anthony Ortiz wrote:
> Pardon my ignorance, but I thought encoding is up to the software and not hardware dependent.

Duly pardoned. Many aspects of encoding are in fact up to the software.
But in the Disk II case, it all has to shift out (and in!) the Disk II
controller. It's a modern marvel of succinct design; I think many of us
consider it Woz's crowning achievement. But its on-board state machine
is not capable of reading and writing completely arbitrary bit patterns.
There are simply some that are verboten. That is why (and this is
hard for newcomers to wrap their head around) there are bit patterns
that exist on disk that it can read, but is not physically capable of
writing. That is the genesis of several effective copy protection schemes.
Re: Reading/Writing C64 disks on Apple // [message #358196 is a reply to message #358186] Fri, 08 December 2017 12:58 Go to previous messageGo to next message
Michael AppleWin Debu is currently offline  Michael AppleWin Debu
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On Friday, December 8, 2017 at 8:22:07 AM UTC-8, schmidtd wrote:
> That is why (and this is
> hard for newcomers to wrap their head around) there are bit patterns
> that exist on disk that it can read, but is not physically capable of
> writing.

Has anyone ever compiled a list of "illegal disk nibbles" that can be read?

i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.
Re: Reading/Writing C64 disks on Apple // [message #358197 is a reply to message #358173] Fri, 08 December 2017 13:48 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: frank_o_rama

https://www.kryoflux.com/?page=home


On Friday, December 8, 2017 at 7:05:01 AM UTC-8, Antoine Vignau wrote:
> I think that the recording format is different. It can be done but with a dedicated disk controller.
>
> Please correct me if I am wrong,
> Antoine
Re: Reading/Writing C64 disks on Apple // [message #358204 is a reply to message #358196] Fri, 08 December 2017 15:31 Go to previous messageGo to next message
qkumba is currently offline  qkumba
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> i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.

Disk II can write lots of consecutive zeroes, it just can't read them all back.
Re: Reading/Writing C64 disks on Apple // [message #358205 is a reply to message #358169] Fri, 08 December 2017 16:01 Go to previous messageGo to next message
Steve Nickolas is currently offline  Steve Nickolas
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If it were me, I'd find a means of hooking an actual 1541 up.

I know it's doable since I've read of two different cases - think I recall
Burger Becky hooking a 1541 to a GS somehow, as the first example I can
think of.

-uso.
Re: Reading/Writing C64 disks on Apple // [message #358206 is a reply to message #358205] Fri, 08 December 2017 16:05 Go to previous messageGo to next message
anthonypaulo is currently offline  anthonypaulo
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Burger Becky explains this in her IIgs Burgertime video
Re: Reading/Writing C64 disks on Apple // [message #358207 is a reply to message #358205] Fri, 08 December 2017 16:29 Go to previous messageGo to next message
David Schmidt is currently offline  David Schmidt
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On 12/8/2017 4:01 PM, Steve Nickolas wrote:
> If it were me, I'd find a means of hooking an actual 1541 up.

Right, because that way you just have to talk the CBM serial protocol to
the 1541 - which already has the CPU and controller built-in to read CBM
GCR. :-)
Re: Reading/Writing C64 disks on Apple // [message #358213 is a reply to message #358206] Fri, 08 December 2017 16:54 Go to previous messageGo to next message
Steve Nickolas is currently offline  Steve Nickolas
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On Fri, 8 Dec 2017, Anthony Ortiz wrote:

> Burger Becky explains this in her IIgs Burgertime video

Yeah, specifically regarding porting "Tass Times in Tonetown". The C64
disk images for that actually have a ProDOS filesystem on them.

-uso.
Re: Reading/Writing C64 disks on Apple // [message #358214 is a reply to message #358207] Fri, 08 December 2017 16:55 Go to previous messageGo to next message
Steve Nickolas is currently offline  Steve Nickolas
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On Fri, 8 Dec 2017, David Schmidt wrote:

> On 12/8/2017 4:01 PM, Steve Nickolas wrote:
>> If it were me, I'd find a means of hooking an actual 1541 up.
>
> Right, because that way you just have to talk the CBM serial protocol to the
> 1541 - which already has the CPU and controller built-in to read CBM GCR.
> :-)
>

Exactly. It's basically a 6502-based computer unto itself.

-uso.
Re: Reading/Writing C64 disks on Apple // [message #358215 is a reply to message #358205] Fri, 08 December 2017 16:56 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Mark D. Overholser

On 08-Dec-17 13:01, Steve Nickolas wrote:
> If it were me, I'd find a means of hooking an actual 1541 up.
>
> I know it's doable since I've read of two different cases - think I
> recall Burger Becky hooking a 1541 to a GS somehow, as the first example
> I can think of.
>
> -uso.


With the Speed of the Commodore C1541, I would almost bet you could
connect it to the Joystick Port with some Level Shifters...

MarkO
Re: Reading/Writing C64 disks on Apple // [message #358217 is a reply to message #358204] Fri, 08 December 2017 18:21 Go to previous messageGo to next message
Michael AppleWin Debu is currently offline  Michael AppleWin Debu
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Ah, yes, sync nibbles should have given it away.

It was my understanding that reading a long sequence of zeroes causes the disk controller to effectively "guess" at the bits -- which causes them to be unreliable, no?

Is it possible to modify the internal state PROM to be more deterministic?
Re: Reading/Writing C64 disks on Apple // [message #358220 is a reply to message #358215] Fri, 08 December 2017 19:44 Go to previous messageGo to next message
Steven Hirsch is currently offline  Steven Hirsch
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A ZoomFloppy and 1541 drive will let you RW diskettes from Windows, Mac or
Linux. If you simply want to move data on and off media it's a good solution.
Re: Reading/Writing C64 disks on Apple // [message #358222 is a reply to message #358196] Fri, 08 December 2017 20:55 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: John Brooks

On Friday, December 8, 2017 at 9:58:37 AM UTC-8, Michael 'AppleWin Debugger Dev' wrote:
> On Friday, December 8, 2017 at 8:22:07 AM UTC-8, schmidtd wrote:
>> That is why (and this is
>> hard for newcomers to wrap their head around) there are bit patterns
>> that exist on disk that it can read, but is not physically capable of
>> writing.
>
> Has anyone ever compiled a list of "illegal disk nibbles" that can be read?
>
> i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.

Yes, there are 81 valid disk nibbles. I prototyped IWM routines on the GS a couple years ago which use them to get 6.3 data bits per disk nibble.

ENCODE81
HEX 92,93,94,95,96,97,99,9A,9B,9C,9D,9E,9F
HEX A4,A5,A6,A7,A9,AA,AB,AC,AD,AE,AF
HEX B2,B3,B4,B5,B6,B7,B9,BA,BB,BC,BD,BE,BF
HEX C9,CA,CB,CC,CD,CE,CF
HEX D2,D3,D4,D5,D6,D7,D9,DA,DB,DC,DD,DE,DF
HEX E4,E5,E6,E7,E9,EA,EB,EC,ED,EE,EF
HEX F2,F3,F4,F5,F6,F7,F9,FA,FB,FC,FD,FE,FF

DECODE81
HEX 80,81,82,83,84,85,86,87,88,89,8A,8B,8C,8D,8E,8F
HEX 90,91,00,01,02,03,04,05,98,06,07,08,09,0A,0B,0C
HEX A0,A1,A2,A3,0D,0E,0F,10,A8,11,12,13,14,15,16,17
HEX B0,B1,18,19,1A,1B,1C,1D,88,1E,1F,20,21,22,23,24
HEX C0,C1,C2,C3,C4,C5,C6,C7,C8,25,26,27,28,29,2A,2B
HEX D0,D1,2C,2D,2E,2F,30,31,D8,32,33,34,35,36,37,38
HEX E0,E1,E2,E3,39,3A,3B,3C,E8,3D,3E,3F,40,41,42,43
HEX F0,F1,44,45,46,47,48,49,F8,4A,4B,4C,4D,4E,4F,50

-JB
@JBrooksBSI
Re: Reading/Writing C64 disks on Apple // [message #358227 is a reply to message #358185] Fri, 08 December 2017 22:44 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
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David Schmidt <schmidtd@my-deja.com> wrote:
> On 12/8/2017 11:10 AM, Anthony Ortiz wrote:
>> That’s what I mean, a change in rotational speed is what’s needed; would
>> it be possible to change the speed by toggling the motor on/off?
>
> Even if you had the time to twiddle the motor on and off while timing
> bits to shift out the write register (which you don't) and it could
> become stable across different drive/motor manufacturers (which it
> wouldn't) you still wouldn't have the ability to write arbitrary (i.e.
> CBM) bit patterns using the Disk II controller.
>

And you can't change the speed by PWMing the motor on signal. Drive speed
is set by a feedback loop, to regulate the drive speed in spite of +12v
fluctuations.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Reading/Writing C64 disks on Apple // [message #358228 is a reply to message #358196] Fri, 08 December 2017 22:44 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
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Michael 'AppleWin Debugger Dev' <michael.pohoreski@gmail.com> wrote:
> On Friday, December 8, 2017 at 8:22:07 AM UTC-8, schmidtd wrote:
>> That is why (and this is
>> hard for newcomers to wrap their head around) there are bit patterns
>> that exist on disk that it can read, but is not physically capable of
>> writing.
>
> Has anyone ever compiled a list of "illegal disk nibbles" that can be read?
>
> i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.
>
>

No, it can write any number of zeros.

The rules for nibbles that can be read are set to provide margin. Some
drives can read some "illegal" nibbles, but not *all* drives. That's why
they are not used.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Reading/Writing C64 disks on Apple // [message #358229 is a reply to message #358217] Fri, 08 December 2017 22:44 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
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Michael 'AppleWin Debugger Dev' <michael.pohoreski@gmail.com> wrote:
> Ah, yes, sync nibbles should have given it away.
>
> It was my understanding that reading a long sequence of zeroes causes the
> disk controller to effectively "guess" at the bits -- which causes them
> to be unreliable, no?
>
> Is it possible to modify the internal state PROM to be more deterministic?
>

No, it's not the state machine. It's the Motorola 3740 (IIRC) which turns
up the gain in the absence of transitions, eventually triggering on noise.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Reading/Writing C64 disks on Apple // [message #358234 is a reply to message #358228] Sat, 09 December 2017 00:58 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: John Brooks

On Friday, December 8, 2017 at 7:44:43 PM UTC-8, Michael J. Mahon wrote:
> Michael 'AppleWin Debugger Dev' wrote:
>> On Friday, December 8, 2017 at 8:22:07 AM UTC-8, schmidtd wrote:
>>> That is why (and this is
>>> hard for newcomers to wrap their head around) there are bit patterns
>>> that exist on disk that it can read, but is not physically capable of
>>> writing.
>>
>> Has anyone ever compiled a list of "illegal disk nibbles" that can be read?
>>
>> i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.
>>
>>
>
> No, it can write any number of zeros.
>
> The rules for nibbles that can be read are set to provide margin. Some
> drives can read some "illegal" nibbles, but not *all* drives. That's why
> they are not used.
>
> --
> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

Hey Michael, as far as I can tell, all 81 disk nibbles are legal from a hardware standpoint. For example, nibble $93 appears to be just as robust as $96.

IMO the 66 'legal' disk nibbles were selected because:

1) D5/AA - half 1s, half 0s. Easily differentiated from $FF sync bytes and the 6&2 data bytes which have consecutive 0 bits or runs of 1 bits.

2) $96-$FF - Single occurrence of consecutive 0 bits. Chosen because the disk controller ROM can algorithmically generate these 64 values with a small 6502 routine.

-JB
@JBrooksBSI
Re: Reading/Writing C64 disks on Apple // [message #358235 is a reply to message #358229] Sat, 09 December 2017 01:05 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: John Brooks

On Friday, December 8, 2017 at 7:44:43 PM UTC-8, Michael J. Mahon wrote:
> Michael 'AppleWin Debugger Dev' wrote:
>> Ah, yes, sync nibbles should have given it away.
>>
>> It was my understanding that reading a long sequence of zeroes causes the
>> disk controller to effectively "guess" at the bits -- which causes them
>> to be unreliable, no?
>>
>> Is it possible to modify the internal state PROM to be more deterministic?
>>
>
> No, it's not the state machine. It's the Motorola 3740 (IIRC) which turns
> up the gain in the absence of transitions, eventually triggering on noise.
>
> --
> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

A couple of experimental findings:

1) When attempting to read 3x consecutive zero bits ($88), 3740 'noise' appears to be caused by the heightened amplification reading an upcoming 1 bit too soon.

2) By decreasing the signal strength (by reading the track 1/4 track away from where it was written), I can read $88 nibbles about 95% of the time instead of 50% of the time.

-JB
@JBrooksBSI
Re: Reading/Writing C64 disks on Apple // [message #358237 is a reply to message #358234] Sat, 09 December 2017 02:58 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
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John Brooks <jbrooks@blueshiftinc.com> wrote:
> On Friday, December 8, 2017 at 7:44:43 PM UTC-8, Michael J. Mahon wrote:
>> Michael 'AppleWin Debugger Dev' wrote:
>>> On Friday, December 8, 2017 at 8:22:07 AM UTC-8, schmidtd wrote:
>>>> That is why (and this is
>>>> hard for newcomers to wrap their head around) there are bit patterns
>>>> that exist on disk that it can read, but is not physically capable of
>>>> writing.
>>>
>>> Has anyone ever compiled a list of "illegal disk nibbles" that can be read?
>>>
>>> i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.
>>>
>>>
>>
>> No, it can write any number of zeros.
>>
>> The rules for nibbles that can be read are set to provide margin. Some
>> drives can read some "illegal" nibbles, but not *all* drives. That's why
>> they are not used.
>>
>> --
>> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
>
> Hey Michael, as far as I can tell, all 81 disk nibbles are legal from a
> hardware standpoint. For example, nibble $93 appears to be just as robust as $96.
>
> IMO the 66 'legal' disk nibbles were selected because:
>
> 1) D5/AA - half 1s, half 0s. Easily differentiated from $FF sync bytes
> and the 6&2 data bytes which have consecutive 0 bits or runs of 1 bits.
>
> 2) $96-$FF - Single occurrence of consecutive 0 bits. Chosen because the
> disk controller ROM can algorithmically generate these 64 values with a small 6502 routine.
>
> -JB
> @JBrooksBSI
>

That makes sense, John.

I'm glad to hear that more than two runs of two zeros in a nibble are
reliably read.

I've always bought the "unreliability" argument until now. I'll do some
more research...but nothing beats experimental evidence!

Are the additional nibbles reliable on a variety of drives?

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Reading/Writing C64 disks on Apple // [message #358266 is a reply to message #358237] Sat, 09 December 2017 12:40 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: John Brooks

On Friday, December 8, 2017 at 11:58:10 PM UTC-8, Michael J. Mahon wrote:
> John Brooks wrote:
>> On Friday, December 8, 2017 at 7:44:43 PM UTC-8, Michael J. Mahon wrote:
>>> Michael 'AppleWin Debugger Dev' wrote:
>>>> On Friday, December 8, 2017 at 8:22:07 AM UTC-8, schmidtd wrote:
>>>> > That is why (and this is
>>>> > hard for newcomers to wrap their head around) there are bit patterns
>>>> > that exist on disk that it can read, but is not physically capable of
>>>> > writing.
>>>>
>>>> Has anyone ever compiled a list of "illegal disk nibbles" that can be read?
>>>>
>>>> i.e. IIRC the Disk II _can_ read two-consecutive zeroes -- it just can't write them.
>>>>
>>>>
>>>
>>> No, it can write any number of zeros.
>>>
>>> The rules for nibbles that can be read are set to provide margin. Some
>>> drives can read some "illegal" nibbles, but not *all* drives. That's why
>>> they are not used.
>>>
>>> --
>>> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
>>
>> Hey Michael, as far as I can tell, all 81 disk nibbles are legal from a
>> hardware standpoint. For example, nibble $93 appears to be just as robust as $96.
>>
>> IMO the 66 'legal' disk nibbles were selected because:
>>
>> 1) D5/AA - half 1s, half 0s. Easily differentiated from $FF sync bytes
>> and the 6&2 data bytes which have consecutive 0 bits or runs of 1 bits.
>>
>> 2) $96-$FF - Single occurrence of consecutive 0 bits. Chosen because the
>> disk controller ROM can algorithmically generate these 64 values with a small 6502 routine.
>>
>> -JB
>> @JBrooksBSI
>>
>
> That makes sense, John.
>
> I'm glad to hear that more than two runs of two zeros in a nibble are
> reliably read.
>
> I've always bought the "unreliability" argument until now. I'll do some
> more research...but nothing beats experimental evidence!
>
> Are the additional nibbles reliable on a variety of drives?
>
> --
> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

My testing was done using the IWM in an Apple IIGS and half-height Apple Unidisk drives. I don't expect a difference in reliability of the 81 legal values between drives or controllers since the read logic always syncs at a 1-bit and must self-clock 2x zero bits after any 1.

For reading 3x zero bits or failing disks, I believe the GS does have an advantage. The GS IWM uses the slot's 7MHz clock and has more accurate self-clocking of 0 bits than the 2MHz state machine in the Disk ][ controller.

-JB
@JBrooksBSI
Re: Reading/Writing C64 disks on Apple // [message #358292 is a reply to message #358229] Sat, 09 December 2017 20:04 Go to previous messageGo to next message
D Finnigan is currently offline  D Finnigan
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Michael J. Mahon wrote:
> Michael 'AppleWin Debugger Dev' <michael.pohoreski@gmail.com> wrote:
>> Ah, yes, sync nibbles should have given it away.
>>
>> It was my understanding that reading a long sequence of zeroes causes the
>> disk controller to effectively "guess" at the bits -- which causes them
>> to be unreliable, no?
>>
>> Is it possible to modify the internal state PROM to be more
>> deterministic?
>>
>
> No, it's not the state machine. It's the Motorola 3740 (IIRC) which turns
> up the gain in the absence of transitions, eventually triggering on noise.
>
>

MC3470
Re: Reading/Writing C64 disks on Apple // [message #358294 is a reply to message #358292] Sat, 09 December 2017 20:35 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
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D Finnigan <dog_cow@macgui.com> wrote:
> Michael J. Mahon wrote:
>> Michael 'AppleWin Debugger Dev' <michael.pohoreski@gmail.com> wrote:
>>> Ah, yes, sync nibbles should have given it away.
>>>
>>> It was my understanding that reading a long sequence of zeroes causes the
>>> disk controller to effectively "guess" at the bits -- which causes them
>>> to be unreliable, no?
>>>
>>> Is it possible to modify the internal state PROM to be more
>>> deterministic?
>>>
>>
>> No, it's not the state machine. It's the Motorola 3740 (IIRC) which turns
>> up the gain in the absence of transitions, eventually triggering on noise.
>>
>>
>
> MC3470
>
>

Thanks!

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: Reading/Writing C64 disks on Apple // [message #358346 is a reply to message #358222] Sun, 10 December 2017 19:01 Go to previous messageGo to next message
Michael AppleWin Debu is currently offline  Michael AppleWin Debu
Messages: 1262
Registered: March 2013
Karma: 0
Senior Member
On Friday, December 8, 2017 at 5:55:56 PM UTC-8, John Brooks wrote:
> On Friday, December 8, 2017 at 9:58:37 AM UTC-8, Michael 'AppleWin Debugger Dev' > Yes, there are 81 valid disk nibbles. I prototyped IWM routines on the GS a couple years ago which use them to get 6.3 data bits per disk nibble.
>
> ENCODE81
> HEX 92,93,94,95,96,97,99,9A,9B,9C,9D,9E,9F
> HEX A4,A5,A6,A7,A9,AA,AB,AC,AD,AE,AF
> HEX B2,B3,B4,B5,B6,B7,B9,BA,BB,BC,BD,BE,BF
> HEX C9,CA,CB,CC,CD,CE,CF
> HEX D2,D3,D4,D5,D6,D7,D9,DA,DB,DC,DD,DE,DF
> HEX E4,E5,E6,E7,E9,EA,EB,EC,ED,EE,EF
> HEX F2,F3,F4,F5,F6,F7,F9,FA,FB,FC,FD,FE,FF
>
> DECODE81
> HEX 80,81,82,83,84,85,86,87,88,89,8A,8B,8C,8D,8E,8F
> HEX 90,91,00,01,02,03,04,05,98,06,07,08,09,0A,0B,0C
> HEX A0,A1,A2,A3,0D,0E,0F,10,A8,11,12,13,14,15,16,17
> HEX B0,B1,18,19,1A,1B,1C,1D,88,1E,1F,20,21,22,23,24
> HEX C0,C1,C2,C3,C4,C5,C6,C7,C8,25,26,27,28,29,2A,2B
> HEX D0,D1,2C,2D,2E,2F,30,31,D8,32,33,34,35,36,37,38
> HEX E0,E1,E2,E3,39,3A,3B,3C,E8,3D,3E,3F,40,41,42,43
> HEX F0,F1,44,45,46,47,48,49,F8,4A,4B,4C,4D,4E,4F,50

Thanks John!
Re: Reading/Writing C64 disks on Apple // [message #358396 is a reply to message #358169] Mon, 11 December 2017 16:50 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: cb meeks

On Friday, December 8, 2017 at 9:05:36 AM UTC-5, Anthony Ortiz wrote:
> I read somewhere that it would be possible to r/w C64 disks on the Disk II if it were possible to change the speed of the drive. Is it that the Disk II is too slow? If not, then perhaps it would be possible to match the C64 disk speed by toggling the drive motor on and off to get the desired speed?

This may have been mentioned already but I don't see why a 1541 couldn't be connected and used with the Apple II. If Arduino's can do it by bit-banging and/or sending serial commands I don't see why an Apple II couldn't do the same.

Especially since the 1541 is a computer itself. In fact, it seems to me that had Woz decided to use the 1541 (assuming it existed in 1977 which it didn't) then he would have had a much easier time just serializing commands to it.

Now the real question then becomes...why would you want to? Not that I'm against it. I think it would be pretty awesome myself.

Even if just to piss off fanboys of all generations and affiliations. :-)
Re: Reading/Writing C64 disks on Apple // [message #358397 is a reply to message #358169] Mon, 11 December 2017 16:52 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: cb meeks

On Friday, December 8, 2017 at 9:05:36 AM UTC-5, Anthony Ortiz wrote:
> I read somewhere that it would be possible to r/w C64 disks on the Disk II if it were possible to change the speed of the drive. Is it that the Disk II is too slow? If not, then perhaps it would be possible to match the C64 disk speed by toggling the drive motor on and off to get the desired speed?

Oh...and I should also mention that if one were to take on such a project, then pretty much nothing would work with it. Custom drivers would have to be written to translate the data from the 1541 to something the A2 could understand and vice-versa. Still, should be doable.
Re: Reading/Writing C64 disks on Apple // [message #358408 is a reply to message #358396] Mon, 11 December 2017 19:31 Go to previous messageGo to next message
Michael AppleWin Debu is currently offline  Michael AppleWin Debu
Messages: 1262
Registered: March 2013
Karma: 0
Senior Member
On Monday, December 11, 2017 at 1:50:48 PM UTC-8, cb meeks wrote:
> This may have been mentioned already but I don't see why a 1541 couldn't be connected and used with the Apple II. ...

> Even if just to piss off fanboys of all generations and affiliations. :-)

Piss off BOTH the Apple 2 _and_ C64 fanboi's? That's would be worth it right there. ;-)
Re: Reading/Writing C64 disks on Apple // [message #358414 is a reply to message #358396] Mon, 11 December 2017 21:06 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: John Brooks

On Monday, December 11, 2017 at 1:50:48 PM UTC-8, cb meeks wrote:
> On Friday, December 8, 2017 at 9:05:36 AM UTC-5, Anthony Ortiz wrote:
>> I read somewhere that it would be possible to r/w C64 disks on the Disk II if it were possible to change the speed of the drive. Is it that the Disk II is too slow? If not, then perhaps it would be possible to match the C64 disk speed by toggling the drive motor on and off to get the desired speed?
>
> This may have been mentioned already but I don't see why a 1541 couldn't be connected and used with the Apple II. If Arduino's can do it by bit-banging and/or sending serial commands I don't see why an Apple II couldn't do the same.
>
> Especially since the 1541 is a computer itself. In fact, it seems to me that had Woz decided to use the 1541 (assuming it existed in 1977 which it didn't) then he would have had a much easier time just serializing commands to it.
>
> Now the real question then becomes...why would you want to? Not that I'm against it. I think it would be pretty awesome myself.
>
> Even if just to piss off fanboys of all generations and affiliations. :-)

BTW: All Datasoft 6502 games (Apple II, Atari, C-64) were duplicated using a modified 1541 connected to an Apple II via a parallel port. That allowed one set of computers & drives to master any of our SKUs.

-JB
@JBrooksBSI
Re: Reading/Writing C64 disks on Apple // [message #358424 is a reply to message #358408] Tue, 12 December 2017 00:22 Go to previous messageGo to next message
Steve Nickolas is currently offline  Steve Nickolas
Messages: 2036
Registered: October 2012
Karma: 0
Senior Member
On Mon, 11 Dec 2017, Michael 'AppleWin Debugger Dev' wrote:

> On Monday, December 11, 2017 at 1:50:48 PM UTC-8, cb meeks wrote:
>> This may have been mentioned already but I don't see why a 1541 couldn't be connected and used with the Apple II. ...
>
>> Even if just to piss off fanboys of all generations and affiliations. :-)
>
> Piss off BOTH the Apple 2 _and_ C64 fanboi's? That's would be worth it right there. ;-)
>

inb4 running a reorganized PET BASIC on an Apple ][ hooked to a 1541.

-uso.
Re: Reading/Writing C64 disks on Apple // [message #358441 is a reply to message #358414] Tue, 12 December 2017 08:36 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: cb meeks

> BTW: All Datasoft 6502 games (Apple II, Atari, C-64) were duplicated using a modified 1541 connected to an Apple II via a parallel port. That allowed one set of computers & drives to master any of our SKUs.
>
> -JB
> @JBrooksBSI

You worked for Datasoft? I'd love to hear more about that.

Oh, and how was the 1541 modified?
Re: Reading/Writing C64 disks on Apple // [message #358488 is a reply to message #358441] Tue, 12 December 2017 20:34 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: John Brooks

On Tuesday, December 12, 2017 at 5:36:32 AM UTC-8, cb meeks wrote:
>> BTW: All Datasoft 6502 games (Apple II, Atari, C-64) were duplicated using a modified 1541 connected to an Apple II via a parallel port. That allowed one set of computers & drives to master any of our SKUs.
>>
>> -JB
>> @JBrooksBSI
>
> You worked for Datasoft? I'd love to hear more about that.
>
> Oh, and how was the 1541 modified?

Yes, I worked at Datasoft from 1987 to 1989 making combat sim games (Tomahawk helicopter flight sim for //e & GS), and sub sim Hunt for Red October for the GS. It was a great company with very talented 6502, 68000, & hardware engineers.

What aspects of the company do you want to know more about?

John Butrovich created the Datasoft disk duplicating system. He also wrote many games and managed the engineering team. Here is his response when I asked how Datasoft duplicated Apple II, Atari, and C64 disks:

On Fri, Aug 4, 2017 at 10:08 AM, John Butrovich wrote:
Actually, I modified the C64 drive to write all 3 formats. I added ram so I could hold a whole track in memory and then write it out in one pass. I seem to recall some logic circuitry for other purposes. It might have been for the write lock gate. Oh, I just remembered I added a parallel interface. It was all controlled with apple II computers.

The warehouse area just behind the dev studio had long tables with Apple II computers lined up in a row. Each Apple had several drives (4x IIRC). The duplication guys would walk along the line, removing freshly written disks, inserting blanks, and keeping all the computers copying full-time.

-JB
@JBrooksBSI
Re: Reading/Writing C64 disks on Apple // [message #358490 is a reply to message #358488] Tue, 12 December 2017 21:19 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Jorge

>
> John Butrovich created the Datasoft disk duplicating system. He also wrote many games and managed the engineering team. Here is his response when I asked how Datasoft duplicated Apple II, Atari, and C64 disks:
>
> On Fri, Aug 4, 2017 at 10:08 AM, John Butrovich wrote:
> Actually, I modified the C64 drive to write all 3 formats. I added ram so I could hold a whole track in memory and then write it out in one pass. I seem to recall some logic circuitry for other purposes. It might have been for the write lock gate. Oh, I just remembered I added a parallel interface. It was all controlled with apple II computers.
>
> The warehouse area just behind the dev studio had long tables with Apple II computers lined up in a row. Each Apple had several drives (4x IIRC). The duplication guys would walk along the line, removing freshly written disks, inserting blanks, and keeping all the computers copying full-time.

That's cool! Those commodore drives had a 6502 inside, right? Fascinating.
--
Jorge.
Re: Reading/Writing C64 disks on Apple // [message #358509 is a reply to message #358488] Wed, 13 December 2017 09:02 Go to previous message
Anonymous
Karma:
Originally posted by: cb meeks

On Tuesday, December 12, 2017 at 8:34:46 PM UTC-5, John Brooks wrote:
> On Tuesday, December 12, 2017 at 5:36:32 AM UTC-8, cb meeks wrote:
>>> BTW: All Datasoft 6502 games (Apple II, Atari, C-64) were duplicated using a modified 1541 connected to an Apple II via a parallel port. That allowed one set of computers & drives to master any of our SKUs.
>>>
>>> -JB
>>> @JBrooksBSI
>>
>> You worked for Datasoft? I'd love to hear more about that.
>>
>> Oh, and how was the 1541 modified?
>
> Yes, I worked at Datasoft from 1987 to 1989 making combat sim games (Tomahawk helicopter flight sim for //e & GS), and sub sim Hunt for Red October for the GS. It was a great company with very talented 6502, 68000, & hardware engineers.
>
> What aspects of the company do you want to know more about?
>

Anything and everything you'd like to share. During 1989 I was bagging groceries at a local store to save money for my Amiga 500. Working for a games company would have been much more interesting. :-)






> On Fri, Aug 4, 2017 at 10:08 AM, John Butrovich wrote:
> Actually, I modified the C64 drive to write all 3 formats. I added ram so I could hold a whole track in memory and then write it out in one pass. I seem to recall some logic circuitry for other purposes. It might have been for the write lock gate. Oh, I just remembered I added a parallel interface. It was all controlled with apple II computers.


That's fascinating!! I mean, the 1541 is a computer in its own right. Fully programmable.


>
> The warehouse area just behind the dev studio had long tables with Apple II computers lined up in a row. Each Apple had several drives (4x IIRC). The duplication guys would walk along the line, removing freshly written disks, inserting blanks, and keeping all the computers copying full-time.
>
> -JB
> @JBrooksBSI


:-) that seriously puts a smile on my face. I miss those days. A simpler time.
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