Megalextoria
Retro computing and gaming, sci-fi books, tv and movies and other geeky stuff.

Home » Digital Archaeology » Computer Arcana » Apple » Apple II » 60hz or 59.94hz?
Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend 
Switch to threaded view of this topic Create a new topic Submit Reply
60hz or 59.94hz? [message #261092] Wed, 16 July 2014 15:16 Go to next message
option8 is currently offline  option8
Messages: 99
Registered: February 2013
Karma: 0
Member
I've been playing around with some small NTSC displays ( e.g. https://www.adafruit.com/products/913 and https://www.adafruit.com/products/947 ). I've found that the larger display will work fine with my Apple IIe and IIc, and the smaller one will not - the video slowly scrolls. Both displays work fine with a Raspberry Pi, however.

I expect this has to do with the display being able to detect and compensate (or not) for the slight difference between a true 60hz signal and a 59.94hz one.

Am I correct in assuming the vintage hardware is at 60.0hz, and the newer Pi is 59.94?

And finally... is there any way to adjust the IIe or IIc to the more modern version of the standard?
Re: 60hz or 59.94hz? [message #261093 is a reply to message #261092] Wed, 16 July 2014 18:36 Go to previous messageGo to next message
Steve Nickolas is currently offline  Steve Nickolas
Messages: 2036
Registered: October 2012
Karma: 0
Senior Member
On Wed, 16 Jul 2014, option8 wrote:

> I've been playing around with some small NTSC displays ( e.g.
> https://www.adafruit.com/products/913 and
> https://www.adafruit.com/products/947 ). I've found that the larger
> display will work fine with my Apple IIe and IIc, and the smaller one
> will not - the video slowly scrolls. Both displays work fine with a
> Raspberry Pi, however.
>
> I expect this has to do with the display being able to detect and
> compensate (or not) for the slight difference between a true 60hz signal
> and a 59.94hz one.

I don't think that's it.

More likely, it's because of NTSC 525 scanlines per frame, and the Apple
only pushing 524. Some displays can cope, others can't.

-uso.
Re: 60hz or 59.94hz? [message #261095 is a reply to message #261092] Wed, 16 July 2014 22:41 Go to previous messageGo to next message
Michael Black is currently offline  Michael Black
Messages: 2799
Registered: February 2012
Karma: 0
Senior Member
On Wed, 16 Jul 2014, option8 wrote:

> I've been playing around with some small NTSC displays ( e.g.
> https://www.adafruit.com/products/913 and
> https://www.adafruit.com/products/947 ). I've found that the larger
> display will work fine with my Apple IIe and IIc, and the smaller one
> will not - the video slowly scrolls. Both displays work fine with a
> Raspberry Pi, however.
>
> I expect this has to do with the display being able to detect and
> compensate (or not) for the slight difference between a true 60hz signal
> and a 59.94hz one.
>
> Am I correct in assuming the vintage hardware is at 60.0hz, and the
> newer Pi is 59.94?
>
> And finally... is there any way to adjust the IIe or IIc to the more
> modern version of the standard?
>
I don't know.

Early tv sets, you had to play with the vertical hold quite a bit. I
remember it as being a regular thing in the sixties and seventies when we
had those "portable" tv sets.

But when I got my first color tv set in 1980, I dont' remember ever
fussing with the vertical hold. Maybe when I used a COmmodore monitor
with a VCR as a tv set in more recent times, but I can't remember that.

When I got an LCD tv set in 2011, there isn't even a method of adjuting
the vertical hold.

Which leaves me thinking something changed, but I cant' remember what the
articles about new tv technology said. They are either better at locking
to the incoming signal, or are locking to some crystal controlled standard
in the tv set, and assuming the incoming signal is on spec.

Michael
Re: 60hz or 59.94hz? [message #261096 is a reply to message #261095] Wed, 16 July 2014 23:27 Go to previous messageGo to next message
Christopher G. Mason is currently offline  Christopher G. Mason
Messages: 156
Registered: November 2012
Karma: 0
Senior Member
On 7/16/2014 10:41 PM, Michael Black wrote:
> I don't know.
>
> Early tv sets, you had to play with the vertical hold quite a bit. I
> remember it as being a regular thing in the sixties and seventies when
> we had those "portable" tv sets.
>
> But when I got my first color tv set in 1980, I dont' remember ever
> fussing with the vertical hold. Maybe when I used a COmmodore monitor
> with a VCR as a tv set in more recent times, but I can't remember that.
>
> When I got an LCD tv set in 2011, there isn't even a method of adjuting
> the vertical hold.
>
> Which leaves me thinking something changed, but I cant' remember what
> the articles about new tv technology said. They are either better at
> locking to the incoming signal, or are locking to some crystal
> controlled standard in the tv set, and assuming the incoming signal is
> on spec.
>
> Michael
>

When VCRs became commonplace, TV manufacturers had to build in tolerance
for out of spec video signals since whatever came off of VHS and Betamax
tapes was far from stable. Modern CRT sets (mid-1970s to present) are
much more forgiving in what they will show. In a way, we have regressed
since many LCDs are extremely picky about what type of signal they will
display.
Re: 60hz or 59.94hz? [message #261130 is a reply to message #261096] Thu, 17 July 2014 00:27 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Don Bruder

In article <lq7fsi$ppr$1@dont-email.me>,
"Christopher G. Mason" <cgm1@my-deja.com> wrote:

> On 7/16/2014 10:41 PM, Michael Black wrote:
>> I don't know.
>>
>> Early tv sets, you had to play with the vertical hold quite a bit. I
>> remember it as being a regular thing in the sixties and seventies when
>> we had those "portable" tv sets.
>>
>> But when I got my first color tv set in 1980, I dont' remember ever
>> fussing with the vertical hold. Maybe when I used a COmmodore monitor
>> with a VCR as a tv set in more recent times, but I can't remember that.
>>
>> When I got an LCD tv set in 2011, there isn't even a method of adjuting
>> the vertical hold.
>>
>> Which leaves me thinking something changed, but I cant' remember what
>> the articles about new tv technology said. They are either better at
>> locking to the incoming signal, or are locking to some crystal
>> controlled standard in the tv set, and assuming the incoming signal is
>> on spec.
>>
>> Michael
>>
>
> When VCRs became commonplace, TV manufacturers had to build in tolerance
> for out of spec video signals since whatever came off of VHS and Betamax
> tapes was far from stable. Modern CRT sets (mid-1970s to present) are
> much more forgiving in what they will show. In a way, we have regressed
> since many LCDs are extremely picky about what type of signal they will
> display.

One of the side-effects of the changeover from analog to digital TV.
Analog gear is, *IN GENERAL*, much more tolerant when it comes to
marginal signal timing. A "wobbling" signal an analog rig will
cheerfully display (even if it might take some twiddling of the vertical
hold knob to get there initially) will often leave a digital rig showing
whatever its particular "can't find a signal" display happens to be.

0.06 Hz doesn't sound like much (and when talking about analog gear, it
really isn't) but it can be more than enough to leave a digital unit
going "Duh... what signal, boss???"

--
Security provided by Mssrs Smith and/or Wesson. Brought to you by the letter Q
Re: 60hz or 59.94hz? [message #261144 is a reply to message #261130] Thu, 17 July 2014 04:38 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
Senior Member
Don Bruder <dakidd@sonic.net> wrote:
> In article <lq7fsi$ppr$1@dont-email.me>,
> "Christopher G. Mason" <cgm1@my-deja.com> wrote:
>
>> On 7/16/2014 10:41 PM, Michael Black wrote:
>>> I don't know.
>>>
>>> Early tv sets, you had to play with the vertical hold quite a bit. I
>>> remember it as being a regular thing in the sixties and seventies when
>>> we had those "portable" tv sets.
>>>
>>> But when I got my first color tv set in 1980, I dont' remember ever
>>> fussing with the vertical hold. Maybe when I used a COmmodore monitor
>>> with a VCR as a tv set in more recent times, but I can't remember that.
>>>
>>> When I got an LCD tv set in 2011, there isn't even a method of adjuting
>>> the vertical hold.
>>>
>>> Which leaves me thinking something changed, but I cant' remember what
>>> the articles about new tv technology said. They are either better at
>>> locking to the incoming signal, or are locking to some crystal
>>> controlled standard in the tv set, and assuming the incoming signal is
>>> on spec.
>>>
>>> Michael
>>>
>>
>> When VCRs became commonplace, TV manufacturers had to build in tolerance
>> for out of spec video signals since whatever came off of VHS and Betamax
>> tapes was far from stable. Modern CRT sets (mid-1970s to present) are
>> much more forgiving in what they will show. In a way, we have regressed
>> since many LCDs are extremely picky about what type of signal they will
>> display.
>
> One of the side-effects of the changeover from analog to digital TV.
> Analog gear is, *IN GENERAL*, much more tolerant when it comes to
> marginal signal timing. A "wobbling" signal an analog rig will
> cheerfully display (even if it might take some twiddling of the vertical
> hold knob to get there initially) will often leave a digital rig showing
> whatever its particular "can't find a signal" display happens to be.
>
> 0.06 Hz doesn't sound like much (and when talking about analog gear, it
> really isn't) but it can be more than enough to leave a digital unit
> going "Duh... what signal, boss???"

The answer can be quickly resolved by looking at the OPs "scrolling".

The Apple II frame rate is also it's field rate, since it's non-interlaced,
and that rate is (nominally) 60Hz. Each field/frame contains exactly 262
lines.

If the 2*262 vs. 525 line format is the issue, the raster should appear to
scroll up a whole screen every 262 60ths of a second, or a little more than
four seconds.

If the monitor is starting a new field 59.94 times per second, even though
vertical sync is occurring 60 times per second, then the raster will appear
to scroll down one whole frame in 1/0.06, or about 17 seconds.
--
-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
Re: 60hz or 59.94hz? [message #261201 is a reply to message #261092] Thu, 17 July 2014 11:09 Go to previous messageGo to next message
Gary Gray is currently offline  Gary Gray
Messages: 14
Registered: February 2013
Karma: 0
Junior Member
On 07/16/2014 03:16 PM, option8 wrote:
> I've found that the larger display will work fine with my Apple IIe and IIc, and the smaller one will not

Can the larger one handle 80 column text?
Re: 60hz or 59.94hz? [message #261272 is a reply to message #261144] Thu, 17 July 2014 14:36 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
Senior Member
Michael J. Mahon <mjmahon@aol.com> wrote:
> Don Bruder <dakidd@sonic.net> wrote:
>> In article <lq7fsi$ppr$1@dont-email.me>,
>> "Christopher G. Mason" <cgm1@my-deja.com> wrote:
>>
>>> On 7/16/2014 10:41 PM, Michael Black wrote:
>>>> I don't know.
>>>>
>>>> Early tv sets, you had to play with the vertical hold quite a bit. I
>>>> remember it as being a regular thing in the sixties and seventies when
>>>> we had those "portable" tv sets.
>>>>
>>>> But when I got my first color tv set in 1980, I dont' remember ever
>>>> fussing with the vertical hold. Maybe when I used a COmmodore monitor
>>>> with a VCR as a tv set in more recent times, but I can't remember that.
>>>>
>>>> When I got an LCD tv set in 2011, there isn't even a method of adjuting
>>>> the vertical hold.
>>>>
>>>> Which leaves me thinking something changed, but I cant' remember what
>>>> the articles about new tv technology said. They are either better at
>>>> locking to the incoming signal, or are locking to some crystal
>>>> controlled standard in the tv set, and assuming the incoming signal is
>>>> on spec.
>>>>
>>>> Michael
>>>>
>>>
>>> When VCRs became commonplace, TV manufacturers had to build in tolerance
>>> for out of spec video signals since whatever came off of VHS and Betamax
>>> tapes was far from stable. Modern CRT sets (mid-1970s to present) are
>>> much more forgiving in what they will show. In a way, we have regressed
>>> since many LCDs are extremely picky about what type of signal they will
>>> display.
>>
>> One of the side-effects of the changeover from analog to digital TV.
>> Analog gear is, *IN GENERAL*, much more tolerant when it comes to
>> marginal signal timing. A "wobbling" signal an analog rig will
>> cheerfully display (even if it might take some twiddling of the vertical
>> hold knob to get there initially) will often leave a digital rig showing
>> whatever its particular "can't find a signal" display happens to be.
>>
>> 0.06 Hz doesn't sound like much (and when talking about analog gear, it
>> really isn't) but it can be more than enough to leave a digital unit
>> going "Duh... what signal, boss???"
>
> The answer can be quickly resolved by looking at the OPs "scrolling".
>
> The Apple II frame rate is also it's field rate, since it's non-interlaced,
> and that rate is (nominally) 60Hz. Each field/frame contains exactly 262
> lines.
>
> If the 2*262 vs. 525 line format is the issue, the raster should appear to
> scroll up a whole screen every 262 60ths of a second, or a little more than
> four seconds.

Oops. Since we're talking what the monitor regards as frames here, it only
slips a line every 30th of a second, so the raster should appear to scroll
up a full frame about every *eight* seconds.

> If the monitor is starting a new field 59.94 times per second, even though
> vertical sync is occurring 60 times per second, then the raster will appear
> to scroll down one whole frame in 1/0.06, or about 17 seconds.


--
-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
Re: 60hz or 59.94hz? [message #261301 is a reply to message #261144] Thu, 17 July 2014 16:57 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Vladimir Ivanov

On Thu, 17 Jul 2014, Michael J. Mahon wrote:

> The Apple II frame rate is also it's field rate, since it's non-interlaced,
> and that rate is (nominally) 60Hz. Each field/frame contains exactly 262
> lines.

NTSC Apple II's refresh rate is about 59.92 Hz, tolerances not included.

Digitally sampling it brings a whole lot of unknowns because of the
software in the controlling MCU trying to "detect" the input signal.
Re: 60hz or 59.94hz? [message #261431 is a reply to message #261092] Fri, 18 July 2014 11:10 Go to previous messageGo to next message
option8 is currently offline  option8
Messages: 99
Registered: February 2013
Karma: 0
Member
here's a quick sample of the scrolling on my //e:

https://drive.google.com/file/d/0BxkaG9mcqJOfUHlwZHphQ0hiN1k
Re: 60hz or 59.94hz? [message #261694 is a reply to message #261431] Sat, 19 July 2014 16:09 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Vladimir Ivanov

On Fri, 18 Jul 2014, option8 wrote:

> here's a quick sample of the scrolling on my //e:
>
> https://drive.google.com/file/d/0BxkaG9mcqJOfUHlwZHphQ0hiN1k

Not exactly scrolling, looks like sampling/sync problem - the MCU (or
circuitry) inside re-tries to lock about once per second. Hence the
garbage pixels.
Re: 60hz or 59.94hz? [message #261695 is a reply to message #261431] Sat, 19 July 2014 16:24 Go to previous messageGo to next message
Bill Garber is currently offline  Bill Garber
Messages: 507
Registered: December 2011
Karma: 0
Senior Member
"option8" <option8@gmail.com> wrote in message
news:5b817768-ab6d-4d3d-b213-05bccf9f04e9@googlegroups.com...
> here's a quick sample of the scrolling on my //e:
>
> https://drive.google.com/file/d/0BxkaG9mcqJOfUHlwZHphQ0hiN1k

WT*? The "Apple //e" should be at the top of the screen, and
then the cursor only if you boot a disk, or you Control-Reset,
in which case the "Apple //e" disappears.

What do you get if you load and list a BASIC program?
Please provide video of that if you decide to do it.

Bill Garber
http://www.sepa-electronics.com
Re: 60hz or 59.94hz? [message #261731 is a reply to message #261695] Sat, 19 July 2014 22:41 Go to previous messageGo to next message
option8 is currently offline  option8
Messages: 99
Registered: February 2013
Karma: 0
Member
> WT*? The "Apple //e" should be at the top of the screen, and

Right. It starts at the top, scrolls off the top and comes back on the bottom of the screen. I let it roll for a few seconds before starting the video.
Re: 60hz or 59.94hz? [message #261732 is a reply to message #261694] Sat, 19 July 2014 22:42 Go to previous message
option8 is currently offline  option8
Messages: 99
Registered: February 2013
Karma: 0
Member
> Not exactly scrolling, looks like sampling/sync problem - the MCU (or
> circuitry) inside re-tries to lock about once per second. Hence the
> garbage pixels.


I've got a couple of other displays in now, so i can try with one of them and see if it's any different. i expect they're all the same, but it's possible i got a gimpy display the first time around.
  Switch to threaded view of this topic Create a new topic Submit Reply
Previous Topic: VSDRIVE pocket serial host finally available
Next Topic: Kids React to the Apple II
Goto Forum:
  

-=] Back to Top [=-
[ Syndicate this forum (XML) ] [ RSS ] [ PDF ]

Current Time: Thu Mar 28 22:20:08 EDT 2024

Total time taken to generate the page: 0.07723 seconds