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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 28th Nov 2023, 9:19 pm   #1
ScottishColin
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Default EPROM questions

You may recall that in my 4032 PET were a couple of EPROMs that I removed whilst fixing it, but found out afterwards that they were utility chips - one called SuperChip and one a Programmer's Toolkit (PAICS).

They're both 2716s.

I've been trying to copy them to 'new' EPROMs so I can take them out 'just in case' however one of them is giving me problems.

I can read the PACIS EPROM fine, I can program a replacement 2716 with its code and verify it but no matter how many I go through it doesn't work when I perform the relevant SYS call on the PET; basically the PET freezes. When I put the original back in (Intel D2716 1977) it's all fine.

None of the replacement ones have been Intels; either Hitachis (HN462716G) or STMicroelectronics (M2716A or M2716FI) ones. but they verify on the Stag EPROM programmer OK.

I suppose the one constant is the (white) socket on the motherboard but the original works fine and I wouldn't mind keeping that socket until it's the last thing to change.

So here's my question; are all 2716s made equal? Is there something about the Hitachis or STMicroelectronics ones that is different?

The Hitachi 2716 works fine when burnt with the PET Tester code so I really don't think it's that.

I suppose once I've eliminated everything, the only remaining thing (white socket) must be the problem?

Any clues gratefully received.

Colin.
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Old 28th Nov 2023, 9:32 pm   #2
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Default Re: EPROM questions

I believe there were different speed devices made, which may be your problem. This can cause problems if the read speed is too slow.
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Old 28th Nov 2023, 9:43 pm   #3
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Default Re: EPROM questions

If you can read the original eprom while its in the pet, save the contents to a file, then compare that with one of your replacements to see if its different.

You might see a pattern in the diferences that could indicate a bad connection.

Its possible your programmer might not be reading the content of the original eprom correctly, then programming the wrong data in the copies.

If you read the original eprom on your programmer, can you then verify a few times. On some programmers they can verify on high and low supply voltage.

Sometimes old eproms can become sensitive to supply voltage. They work on stored charge and the read operation compares the stored charge with a threshold to determine 0 or 1. As they age the charge can dissipate, they were mostly specified to last ten years. There were also various fast programming algorithms that reduced programming time, but might not be so permanent as the full standard algorithms.
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Old 28th Nov 2023, 10:26 pm   #4
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Default Re: EPROM questions

I've read it OK and saved it.

The process I was using was to load from the EPROM to the Stag memory, then write that back out again and compare the 'new' 2716 to the Stag memory and that's OK. I guess it's possible that I haven't actually read it properly?

I can't find a copy of the EPROM out on the internet to check that I've read it properly; all the ones on Zimmers are different to the one I saved earlier (But I guess if I haven't read it properly then that may be the case).

I'll see if I can hunt a PAICS toolkit dated 1980 out there anywhere on the internet.....

Colin.



Quote:
Originally Posted by Mark1960 View Post
If you can read the original eprom while its in the pet, save the contents to a file, then compare that with one of your replacements to see if its different.

You might see a pattern in the diferences that could indicate a bad connection.

Its possible your programmer might not be reading the content of the original eprom correctly, then programming the wrong data in the copies.

If you read the original eprom on your programmer, can you then verify a few times. On some programmers they can verify on high and low supply voltage.

Sometimes old eproms can become sensitive to supply voltage. They work on stored charge and the read operation compares the stored charge with a threshold to determine 0 or 1. As they age the charge can dissipate, they were mostly specified to last ten years. There were also various fast programming algorithms that reduced programming time, but might not be so permanent as the full standard algorithms.
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Old 28th Nov 2023, 10:54 pm   #5
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Default Re: EPROM questions

OK - I took the file toolkit4.0_alt-a000.bin from Zimmers and burnt that and it works fine. I can only conclude that my EPROM programmer couldn't/didn't read the original contents properly.

Colin.
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Old 28th Nov 2023, 11:08 pm   #6
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Default Re: EPROM questions

Put the original working 2716 in the programmer, have the programmer checksum the device and note the 16-bit checksum value.

Remove the original EPROM, drop one of your verified copies into the programmer and have the programmer checksum that device. Do the checksums match?

When you program a device and it verifies successfully, that only means that the programmer succeeded in programming it with the code you told it to programme into the device.

Remember that the sockets in the PET, apart from the 'edit' ROM which is a special case, all expect, and are pinned for, 4K ROMs with an A11 pin on pin 18 and a chip-enable signal going to pin 20 and steady +5V going to pin 21.

Although you've said the original code does appear to run in the 2716 it came in, try programming the code you read out of the original 2716 into one of your 2532s, doubled-up (same code in the lower half and the upper half). Does it run then?

Edit: Crossed with Colin's last post above.
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Old 28th Nov 2023, 11:36 pm   #7
ScottishColin
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Default Re: EPROM questions

This is the first time (in admittedly not many times) that I've not been able to read/burn an EPROM.

It's strange that it read and verified, but clearly wasn't the right image.

One of those things I guess; old tech eh?

Colin.

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Originally Posted by SiriusHardware View Post
Put the original working 2716 in the programmer, have the programmer checksum the device and note the 16-bit checksum value.

Remove the original EPROM, drop one of your verified copies into the programmer and have the programmer checksum that device. Do the checksums match?

When you program a device and it verifies successfully, that only means that the programmer succeeded in programming it with the code you told it to programme into the device.

Remember that the sockets in the PET, apart from the 'edit' ROM which is a special case, all expect, and are pinned for, 4K ROMs with an A11 pin on pin 18 and a chip-enable signal going to pin 20 and steady +5V going to pin 21.

Although you've said the original code does appear to run in the 2716 it came in, try programming the code you read out of the original 2716 into one of your 2532s, doubled-up (same code in the lower half and the upper half). Does it run then?

Edit: Crossed with Colin's last post above.
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Old 29th Nov 2023, 2:13 am   #8
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Default Re: EPROM questions

This was why I suggested you read the old eprom data in the pet, as you said it was running in the pet, then check if reading one of your copies in the pet was showing the same data. If the pet is running with the old eprom but not reading correctly on the programmer this suggests the old eprom is close to failing.
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Old 29th Nov 2023, 9:37 am   #9
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Default Re: EPROM questions

if the original EPROM runs OK in the PET where it is resident then a useful exercise might be to write a BASIC program which PEEKs the value in each location of the EPROM, and writes them out to a file on your SD2PET from which you may possibly be able to copy it onto a PC?

I don't know if PET BASIC can write binary files but if not, then the workaround would be to write it to a file as ASCII HEX or Intel Hex, both of which are basically text files.

Is the built in monitor able to load and save binary files and if so, can it save them to 'disc' as well as to tape?
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Old 29th Nov 2023, 11:11 am   #10
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Default Re: EPROM questions

Just a list of the 2048 'peeked' decimal numbers would suffice,
its easy to convert that off-board to bin, hex, whatever
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Old 29th Nov 2023, 11:27 am   #11
ScottishColin
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Default Re: EPROM questions

I'd missed the "reading it on the PET" bit; apologies.

I'll go knock up some BASIC today when work allows.

Colin.

Quote:
Originally Posted by Mark1960 View Post
This was why I suggested you read the old eprom data in the pet, as you said it was running in the pet, then check if reading one of your copies in the pet was showing the same data. If the pet is running with the old eprom but not reading correctly on the programmer this suggests the old eprom is close to failing.
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Old 29th Nov 2023, 11:28 am   #12
ScottishColin
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Default Re: EPROM questions

Yes - this is all possible.

I can print it too on my Commodore printer....I like hardcopy

Colin.

Quote:
Originally Posted by SiriusHardware View Post
if the original EPROM runs OK in the PET where it is resident then a useful exercise might be to write a BASIC program which PEEKs the value in each location of the EPROM, and writes them out to a file on your SD2PET from which you may possibly be able to copy it onto a PC?

I don't know if PET BASIC can write binary files but if not, then the workaround would be to write it to a file as ASCII HEX or Intel Hex, both of which are basically text files.

Is the built in monitor able to load and save binary files and if so, can it save them to 'disc' as well as to tape?
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Old 29th Nov 2023, 2:53 pm   #13
ScottishColin
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Default Re: EPROM questions

So from a brief inspection (first 8 bytes), the original EPROM is the same as the file toolkit4.0_alt-a000.bin from Zimmers. As is the one I burnt as a replacement (unsurprisingly). But very different to that which the Stag reads.

I'll work on getting the whole 2048 bytes in a file just for fun.

Colin.
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Old 29th Nov 2023, 3:17 pm   #14
ScottishColin
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Default Re: EPROM questions

OK - here's the 2K from the PET dumped using the instructions here:

https://vintagecomputer.net/browse_thread.cfm?id=287

There's two differences:

"Compare error at OFFSET 46D
file1 = F4
file2 = F5
Compare error at OFFSET 6A4
file1 = B2
file2 = B1"

But I do not have a .bin file for the EPROM so it's possible they are either errors in reading (although the EPROM works) or there have been two small changes between the version I have and the one I downloded from Zimmers.

Colin.
Attached Files
File Type: txt PAICS Mem Dump.txt (2.0 KB, 17 views)
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Old 29th Nov 2023, 3:57 pm   #15
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Default Re: EPROM questions

At a glance, that looks good, it has recognisable ascii messages in there, "RENUMBER", "DELETE", "OUT OF RANGE" etc and "(c) 1980 PAICS"
I cant comment on the code as I've no 6502 experience at all
Heres the same file in Intel hex format (both F4/B2 and F5/B1 versions):
Attached Files
File Type: zip paics2716.zip (5.4 KB, 7 views)

Last edited by Phil__G; 29th Nov 2023 at 4:18 pm.
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Old 29th Nov 2023, 4:13 pm   #16
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Default Re: EPROM questions

The differences could just be due to the fact that it is a previously un-archived sub-version of the utility.

Try programming the file exactly as read out from the original EPROM by the PET, into another 2716 and see what happens.
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Old 29th Nov 2023, 5:42 pm   #17
ScottishColin
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Default Re: EPROM questions

That worked, as I suppose it ought to as it's byte for byte the same as the original EPROM that came out of the PET.

So what have I learnt?

1) that my Stag can't read every EPROM (even though is apparently worked)
2) that I now know how to dump an area of memory from the PET to a file and transfer it to my PC to program anew on the Stag.

Colin.


Quote:
Originally Posted by SiriusHardware View Post
The differences could just be due to the fact that it is a previously un-archived sub-version of the utility.

Try programming the file exactly as read out from the original EPROM by the PET, into another 2716 and see what happens.
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Old 29th Nov 2023, 5:55 pm   #18
ScottishColin
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Default Re: EPROM questions

For those with plenty of time, the original author reconstructed the source code from a disassembly of the ROM here (with manuals, adverts photos etc):

https://github.com/LenShustek/Nestar...'s_Toolkit

Colin.
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Old 29th Nov 2023, 7:18 pm   #19
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Default Re: EPROM questions

Quote:
Originally Posted by ScottishColin View Post
1) that my Stag can't read every EPROM (even though is apparently worked)
Station X had a similar problem recently
https://www.vintage-radio.net/forum/...to_threadtools
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Old 30th Nov 2023, 1:11 am   #20
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Default Re: EPROM questions

Quote:
2) that I now know how to dump an area of memory from the PET to a file and transfer it to my PC to program anew on the Stag.
To be honest I think it was a good thing you were, in a sense, forced to add that to your skill set, as you now have two different ways of reading certain types of EPROM (actually three because you could also have attempted to use your Arduino Mega to read it, as that approach did work in the thread Mark linked to above).
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