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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 14th Aug 2023, 9:31 pm   #661
ScottishColin
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Default Re: Commodore PET 4032/8050/3022

Right - here's a full list of what was replaced on the motherboard. It's more than I thought.

6520 x 2
6522
6502
6545
MC3446 x 3
7417
74244 x 7
74145
74154
2114 x 2
74164

On the CRT board, we replaced 2 x resistors and a capacitor.

Colin.
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Old 14th Aug 2023, 11:47 pm   #662
SiriusHardware
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Default Re: Commodore PET 4032/8050/3022

I would say you can quietly lose a couple of those from the list. The 74154 (UE12) was wrongly blamed for an address problem when in fact there was a problem with the connection from one of the NOP tester output lines. The 7417 was an early attempt to work out what was dragging down the reset line, that turned out to be the original UB16. The main data bus buffers were removed so they could be tested in the UD13 / UD14 position but I think they proved to be OK, so if you only want to list what needed to be replaced you can probably lose all of those - unless you want to follow the whole process, wrong turns and all, which is fair enough.

Please do post the .bin code of those two EPROMs and we'll see if we can match them up with anything on zimmers. Just to be sure, the one labelled Superchip, which socket did you find that one in, UD11 or UD12? The Superchip files on zimmers seem to be written to reside at 9000 which would be the UD12 position.

As far as I can make out Superchip is some kind of editor enhancement although, not being familiar with the PET's UI, I don't know why the editor would need enhancing unless it adds features like select and block-copy, etc.
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Old 15th Aug 2023, 12:30 am   #663
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Default Re: Commodore PET 4032/8050/3022

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Originally Posted by Mark1960 View Post
Quote:
Originally Posted by ortek_service View Post
(I once found a Z80A CPU IC that only worked for about 30s, but did work for longer if sprayed with freezer spray - Well butane lighter refill fluid, as that was all I had to hand! - to prove it was at fault).
That should probably have a warning “Don’t try this at home”.
Well a small amount of it sprayed on the IC wasn't too dangerous, as it soon evaporates (but maybe avoid breathing butane etc gas in, as can be lethal!).
(And many PCB-cleaning fluids - especially back then - were rather inflammable)

Maybe more of a H&S issue, was that so much leaked out onto your hands, when trying to find an adaptor that actually fitted properly, when trying to refill a cigarette lighter - That I only used for heat-shrinking, lighting a candle to drop hot wax onto RF coils, and heating an adjustment tool's copper blade, (to adjust wax-sealed Toko coils and heat would conduct through the Ferrite to allow it to turn freer with less risk of it breaking). So maybe all things that could be slightly-dangerous!
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Old 15th Aug 2023, 12:41 am   #664
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Default Re: Commodore PET 4032/8050/3022

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Ah well. If I put the Superchip EPROM in, the PET won't boot at all - I just get a single left-arrow on the screen.

The PET boots with the unmarked ROM on its own, but I can't get it to do anything.

I'll take a memory dump of each EPROM and pop them on here to see if anyone can make anything of them but having got the PET working, I think I'll put them to one side now.

Colin.
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Originally Posted by SiriusHardware View Post
>>
Please do post the .bin code of those two EPROMs and we'll see if we can match them up with anything on zimmers. Just to be sure, the one labelled Superchip, which socket did you find that one in, UD11 or UD12? The Superchip files on zimmers seem to be written to reside at 9000 which would be the UD12 position.

As far as I can make out Superchip is some kind of editor enhancement although, not being familiar with the PET's UI, I don't know why the editor would need enhancing unless it adds features like select and block-copy, etc.

I wonder if the 'Superchip' manages to intercept control, before BASIC launches, and the single left-arrow is a prompt for a keypress / command entry etc? - If there's documentation out there for it, then maybe that might help to show how it is meant to work..

The unmarked ROM may be a bit of a disassembly-challenge to anyone, to work-out a likely entry-point / if it is intended to work in conjunction with the Superchip EPROM - I also presume you did try both in at the same time, as when you got this 4032?
So posting contents of these here, will no doubt result in a few people trying to work-out what they should be doing.

Of course the contents may well have got corrupted in these over the years, so may be a reason why they don't seem to do much. It's strange / a pity thee doesn't seem to be any readable ASCII text in these (which could also indicate bad-corruption of contents, if 'Utility' ROM's did usually have some text / copyright messages in them).

Last edited by ortek_service; 15th Aug 2023 at 1:00 am.
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Old 15th Aug 2023, 12:56 am   #665
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Default Re: Commodore PET 4032/8050/3022

Quote:
Originally Posted by ScottishColin View Post
Right - here's a full list of what was replaced on the motherboard. It's more than I thought.

6520 x 2
6522
6502
6545
MC3446 x 3
7417
74244 x 7
74145
74154
2114 x 2
74164

On the CRT board, we replaced 2 x resistors and a capacitor.

Colin.

Quote:
Originally Posted by SiriusHardware View Post
I would say you can quietly lose a couple of those from the list. The 74154 (UE12) was wrongly blamed for an address problem when in fact there was a problem with the connection from one of the NOP tester output lines. The 7417 was an early attempt to work out what was dragging down the reset line, that turned out to be the original UB16. The main data bus buffers were removed so they could be tested in the UD13 / UD14 position but I think they proved to be OK, so if you only want to list what needed to be replaced you can probably lose all of those - unless you want to follow the whole process, wrong turns and all, which is fair enough.
>>
>>
Well 21 - 2 still leaves 19off failed IC's! (So comparable with the 3016?)
- Although not sure if this includes any ones that legs got accidentally detached.
(Or if the 7off 74Ls244's included all 3off of the recently-removed UE8,9,10 ones, and whether more than one of those had been found to be actually faulty?)

What has probably been most useful, is having a few spares of these / another PET with these socketed, to be a temporary donor
- Ordering all 19off of these with many separate orders as each was found / suspected to have been faulty could get rather expensive in multiple order fees! And would no doubt have ended-up ordering some ones that were suspect, but were then found to be actually OK, when swapped, and fault was elsewhere.

Whereas, now only need to do the minimum number of orders to get replacements (+ maybe the odd future spare, for the relatively-cheap IC's).

Last edited by ortek_service; 15th Aug 2023 at 1:20 am.
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Old 15th Aug 2023, 1:07 am   #666
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Default Re: Commodore PET 4032/8050/3022

Looking through the files under the link Colin posted a little bit further back I found these - these are just filenames, you will need to go to zimmers to search for and find the actual files.

The first is a manual, the second a quick reference guide.

Quote:
superchip-toolkit.txt

PetMaster_Superchip_QuickRef.pdf

superchip-9000.bin

superchip40-9000.bin
The last two seem to be early and later versions of Superchip, the second one being V4.0. I downloaded the last file and did find some plaintext in it, mainly BASIC keywords.
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Old 15th Aug 2023, 1:29 am   #667
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Default Re: Commodore PET 4032/8050/3022

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>>

>>


The last two seem to be early and later versions of Superchip, the second one being V4.0. I downloaded the last file and did find some plaintext in it, mainly BASIC keywords.
I wonder if / how many of those Keywords are in addition to that in PET BASIC (4.0) ?
It's been quite a while since I last used a PET, but most of those I would have thought would be standard PET BASIC Keywords.
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Old 15th Aug 2023, 8:09 am   #668
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Default Re: Commodore PET 4032/8050/3022

Well, PEEK and POKE are certainly keywords in standard PET BASIC. Reading through the quick reference, second document in the list in #666 it seems possible that the Superchip adds one-letter shorthand for many of the common BASIC keywords. If so I'm not sure that would serve any purpose other than to make the code nearly unreadable, although it might conceivably make the BASIC interpreter run faster if it doesn't have to parse the whole keyword each time it finds it in a line of BASIC.

Maybe what it does is to allow entry of a line in shorthand form, which the editor then expands to the full normal syntax when you hit enter to add the line of code to the program.
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Old 15th Aug 2023, 10:31 am   #669
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Default Re: Commodore PET 4032/8050/3022

Colin could always make a Superchip EPROM by programming a 2532 with one of the .bin files referenced in #666 and try putting it in the UD12 position. The documentation also referred to in #666 appears to suggest that nothing will happen until you activate the EPROM by running a SYS (startaddress) command.

I really must try to get VICE (the Commodore emulator) up and running as it would make playing with this sort of thing very easy (for someone who doesn't have a PET).
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Old 15th Aug 2023, 10:44 am   #670
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Default Re: Commodore PET 4032/8050/3022

Two files attached - the Superchip is a NatSemi 2716G and I can see text in there using HxD.

The EPROM with a readable label (here as blankv2.bin) is an Intel 2716G and doesn't have any text I can see.

When I received the PET, the chip with the unreadable label was in UD11 and the Superchip in UD12. Both of those two sockets are the last remaining unreplaced white sockets btw.

Colin.
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Old 15th Aug 2023, 11:20 am   #671
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Default Re: Commodore PET 4032/8050/3022

Just had a quick look at the Superchip code from the one in your machine, I'm afraid it is slightly different from either of the SC code files available from Zimmers, all three have different checksums and crucially the descriptive text at the end of the EPROM differs slightly between each one, so between you and zimmers, that's three different versions.

With no file copy of your version on zimmers to make a direct comparison with, we can not unfortunately say whether your version is whole or corrupt.
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Old 15th Aug 2023, 1:59 pm   #672
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Default Re: Commodore PET 4032/8050/3022

I'll burn the superchip40-9000.bin just to see what it should look like.

Colin.
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Old 15th Aug 2023, 2:25 pm   #673
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Default Re: Commodore PET 4032/8050/3022

From what little I have had time to read I think you have to invoke it with a SYS command, so the machine should just boot normally with it inserted with no obvious effect until you do the SYS.

After that the RUN/STOP key functions like a CTRL key with various CRTL + Key combinations providing functions not normally available in the standard editor.
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Old 15th Aug 2023, 2:40 pm   #674
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Default Re: Commodore PET 4032/8050/3022

There are a couple of pages about Superchip starting at page 12 of this (user group) newsletter. This repeats the statement found in the text file on zimmers, that superchip is intended to work in conjunction with 'Toolkit' which might be what is supposed to be in that other EPROM.

http://archive.6502.org/publications...1_jan_1981.pdf

That whole series of newsletters could be very interesting to read if they are all archived there.
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Old 15th Aug 2023, 3:47 pm   #675
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Default Re: Commodore PET 4032/8050/3022

Saw your 'wanted' ad for replacement 6522 / 6520s, I think maybe the 6522 can't be substituted but there is apparently a currently produced chip, the WDC W65C21N, which is a drop in replacement for the 6520.

Have a look at AJ's old PET repair thread from about here on:

https://www.vintage-radio.net/forum/...=174919&page=9

While I appreciate you would probably prefer to keep it real (all original devices) those would at least allow you to put your other parts back in the 3016.
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Old 15th Aug 2023, 4:49 pm   #676
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Default Re: Commodore PET 4032/8050/3022

That's interesting. I have found 3 x 6522s here - I'll go hunt for the WDC W65C21N as suggested.

Colin.

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Originally Posted by SiriusHardware View Post
Saw your 'wanted' ad for replacement 6522 / 6520s, I think maybe the 6522 can't be substituted but there is apparently a currently produced chip, the WDC W65C21N, which is a drop in replacement for the 6520.

Have a look at AJ's old PET repair thread from about here on:

https://www.vintage-radio.net/forum/...=174919&page=9

While I appreciate you would probably prefer to keep it real (all original devices) those would at least allow you to put your other parts back in the 3016.
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Old 15th Aug 2023, 4:56 pm   #677
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Default Re: Commodore PET 4032/8050/3022

How about the MC6821? I have found a couple of threads suggesting that's a replacement and I can get them from Cricklewood. I can't easily find the W65C21N.

Colin.
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Old 15th Aug 2023, 5:01 pm   #678
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Default Re: Commodore PET 4032/8050/3022

I can send you a couple of MC6821 Colin, they're pin compatible and the 6520 datasheet says its "a high performance replacement for the Motorola PIA"
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Old 15th Aug 2023, 5:03 pm   #679
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Default Re: Commodore PET 4032/8050/3022

Thanks Phil -that's very kind. I'll PM you my address.

Colin.


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I can send you a couple of MC6821 Colin, they're pin compatible and the 6520 datasheet says its "a high performance replacement for the Motorola PIA"
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Old 15th Aug 2023, 5:23 pm   #680
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Default Re: Commodore PET 4032/8050/3022

What exactly is the difference between the 6520 and the 6521, does anyone know? I can't fathom the logic(!) of making functionally identical ICs with side by side numbers, although on rare occasions there is the realisation that a well known / well used chip has some weakness or bug, so a 'MK2' version gets made which has a slightly different IC number, but is presented as a better alternative to the original. Presumably that is what has happened here?
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