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Misc. Discussion 1541/2031/4040/2040 [message #83292] Mon, 10 June 2013 21:28 Go to next message
Anonymous
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Originally posted by: dillon@ucbvax.ARPA (The Sherif "Matt D.")
Message-ID: <3957@ucbvax.ARPA>
Date: Sat, 29-Dec-84 16:29:38 EST
Article-I.D.: ucbvax.3957
Posted: Sat Dec 29 16:29:38 1984
Date-Received: Sat, 29-Dec-84 20:04:09 EST
Distribution: net
Organization: University of California at Berkeley
Lines: 73


Let me tell you a story about these drives.  The first, the 2040, is a
duel drive whos age is beyond counting.  At one point commodore decided
that the 2040 format was creating errors (It had one extra sector on 
several tracks).  So, they modified the format slightly by taking out that
sector.  That is why the OLD 2040 has more storage than the NEW 1541/2031/
4040.  Now, Commodore tells us that the 1541, 2031, and 4040 have the same
disk format.  Bryce pointed out to me one day as we were muling over the
hundreds of errors (not to mention the bad programming style) of the 1541
DOS, that the 4040 uses a different spacing between sectors.  Oh JUST GREAT...
I suggest that to keep read errors at a minimum, you not write on a disk 
using a 1541 that was formatted on a 4040.  

Guess what!  Commodore did not write a new DOS for the 1541 or the 2031. 
In fact, the used the 4040's DOS and attempted to take out all the references
to the second drive.  Well, they just didn't get them all and that is why
you get that DRIVE NOT READY error sometimes.  Their @replace bug was a 
classic, and that was one of the first thing Bryce fixed in his 1541 FLASH.

But the story does not end there.  Word has it that two people worked on 
the original DOS for the 1541/2031/4040/2040.  One wrote the drive interface,
and one wrote the communications protocal.  Word also has it that the two
hardly confered with each other at all... Hence the slowness of drive.

You have to be an expert on 6502 to be able to understand the drive's DOS,
considering how lousy the guy programmed it.  Why commodore used a modem-
speed interface with an intelligent disk drive I could not guess.

I myself am a PET person.  The best transfer speed I've been able to come
up with a PET & 2031 has been 53KBytes/sec ... With sector loading, I've
been able to get a skew factor of 3 and a 130 block load in 6.5 sec.  Bryce
has been able to turn the rinky-dink serial interface into exactly the same
speed... Were both stuck on the skew factor.  I think that's pretty good
considering the controller Commodore used for the disk (It consists of a
micro-processor, 2K RAM, 16K ROM, and 2 6522's.  None of these, by the way,
are dedicated as a floppy controller).

And now we come to the (quote unquote) Build in RS-232C.  The C64 does it all
in software, and the outputs are +5/GND rather than standard -12/12V.  Baud
rates below 2400 work fine.  Anything after that will not work well unless
you do it by hand.  Commodore has this nack of putting everything on the 
interrupt, you see; They put the disk-controller of the 1541... on the
interrupt.  I'm not kidding, to request a sector you wrote some crap into
some memory and had to wait for a timer interupt to occur before the 
interrupt service routine would catch it and get/write the sector.  In
anycase, I'm getting off the subject;  Commodore has the modem on the 
interrupt.  So as long as you don't use the disk drive or printer, you
can use the modem.  You can either recieve or transmit (but not both at
the same time).  In other words, commodore blew it again in terms of the
C64.


You might ask if there is anything good about the commodore 64. Well, the
graphics are good and the sound is fantastic.  Don't let anyone tell you
the sound is the pits... I've heard very un-computer like voice synthesis
using only that single solitary SID.  The graphics are good, considering
that the C64 is only a small home computer.  I particulary like the raster
interrupt which makes it all worth while.  You probably have heard that at
any time the graphics chip can take 40cc from the processor.  Well, using
the raster interrupt, Bryce was able to sync the two and to a VERY FAST
trasfer over the original serial lines sync'd with the drive to within
3cc (On my PET, I used to use a single sync signal to sync the block transfers,
Giving me a 32KByte/sec ifc with 8cc tolerances.  Bryce suggested a double
sync to sync the sync, so to speak, which is why I can do 56KBytes/sec over
IEEE and he can do 20KBytes/sec over the original lines.  With 1541 FLASH,
the thoretical maximum is about the same as my IEEE transfers.  In either
case the transfer is 1000% better than Commodores, and the only holding 
factor is that the data must be read off disk before it can be sent over).


				Matthew Dillon (dillon@vax.Berkeley.ARPA)
Re: Misc. Discussion 1541/2031/4040/2040 [message #83294 is a reply to message #83292] Mon, 10 June 2013 21:28 Go to previous messageGo to next message
wjr is currently offline  wjr
Messages: 26
Registered: May 2013
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Message-ID: <309@utcs.UUCP>
Date: Sun, 30-Dec-84 00:09:33 EST
Article-I.D.: utcs.309
Posted: Sun Dec 30 00:09:33 1984
Date-Received: Sun, 30-Dec-84 01:09:04 EST
References: <3957@ucbvax.ARPA>
Reply-To: wjr@utcs.UUCP (William Rucklidge)
Distribution: net
Organization: University of Toronto - General Purpose UNIX
Lines: 15
Summary: 

In article <3957@ucbvax.ARPA> dillon@ucbvax.ARPA (The Sherif "Matt D.") writes:
>                                               Why commodore used a modem-
> speed interface with an intelligent disk drive I could not guess.


I could: it's cheap. The cables are DIN 6-pin, and it requires only
a few bits of I/O. It may take a few more man-years to program, but
Commodore has made millions of VICs/C64s/1541s and even a dollar
saved per unit in hardware makes up for a lot of software overhead.
-- 

"You can always put something in a box."
This message brought to you with the aid of the Poslfit Committee.
William Rucklidge	University of Toronto Computing Services
{decvax,ihnp4,utcsrgv,{allegra,linus}!utzoo}!utcs!wjr
Re: Misc. Discussion 1541/2031/4040/2040 [message #83298 is a reply to message #83292] Mon, 10 June 2013 21:28 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: dillon@ucbvax.ARPA (The Sherif "Matt D.")
Message-ID: <3974@ucbvax.ARPA>
Date: Mon, 31-Dec-84 07:40:27 EST
Article-I.D.: ucbvax.3974
Posted: Mon Dec 31 07:40:27 1984
Date-Received: Tue, 1-Jan-85 00:50:40 EST
References: <3957@ucbvax.ARPA> <309@utcs.UUCP>
Distribution: net
Organization: University of California at Berkeley
Lines: 23

> In article <3957@ucbvax.ARPA> dillon@ucbvax.ARPA (The Sherif "Matt D.") writes:
> >                                               Why commodore used a modem-
> > speed interface with an intelligent disk drive I could not guess.
> 
> 
> I could: it's cheap. The cables are DIN 6-pin, and it requires only
> a few bits of I/O. It may take a few more man-years to program, but
> Commodore has made millions of VICs/C64s/1541s and even a dollar
> saved per unit in hardware makes up for a lot of software overhead.
> -- 
> 
> "You can always put something in a box."
> This message brought to you with the aid of the Poslfit Committee.
> William Rucklidge	University of Toronto Computing Services
> {decvax,ihnp4,utcsrgv,{allegra,linus}!utzoo}!utcs!wjr

Yes! But Commodore could have used the same two serial clock and data lines
and connected them up to UNUSED hardware shift registers (The drive has one,
the C64 has two).	Frankly, This simple change (let's face it, there ARE
some idiots at Commodore) would have given the 1541 IEEE speeds as well reduced
the cost of the drive.
Re: Misc. Discussion 1541/2031/4040/2040 [message #85963 is a reply to message #83292] Mon, 17 June 2013 17:35 Go to previous message
dave is currently offline  dave
Messages: 135
Registered: February 2013
Karma: 0
Senior Member
Message-ID: <1731@zehntel.UUCP>
Date: Fri, 4-Jan-85 04:18:48 EST
Article-I.D.: zehntel.1731
Posted: Fri Jan  4 04:18:48 1985
Date-Received: Sun, 6-Jan-85 01:08:57 EST
Sender: berry@zehntel.UUCP
Organization: Zehntel Automation Systems Inc, Walnut Creek CA
Lines: 23
Nf-ID: #R:ucbvax:-100:zinfandel:19800017:000:754
Nf-From: zinfandel!dave    Jan  2 10:30:00 1985

<>

>Guess what!  Commodore did not write a new DOS for the 1541 or the 2031. 
>In fact, the used the 4040's DOS and attempted to take out all the references
>to the second drive.  Well, they just didn't get them all and that is why
>you get that DRIVE NOT READY error sometimes.  Their @replace bug was a 
>classic, and that was one of the first thing Bryce fixed in his 1541 FLASH.

In the 1541 FLASH manual, the author makes a *special point* of the fact
that they DID NOT fix the @replace bug.  They even go through a short 
explanation of why they think this bug pops up now and again. 


Dave Funk
Zehntel, Inc.
2625 Shadelands Drive
Walnut Creek, CA  92598
(415) 932-6900 x309

     ....!decvax!sytek!zehntel!dave
     ...."zehntel!dave"@BERKELEY
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