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What ROM type?

E

eight088

Experienced Member
Joined
Oct 31, 2018
Messages
158
Location
Perth, WA Australia
Hi

I just got my GQ-4x4 programmer, and I'm wanting to read the roms from a pet 8032. The writing on the rom is 901465-21. Before I do, I just wanted to know what type of rom I would select in usb prg in case choosing the wrong one can damage the rom? I think 2532 roms are a replacement so can I select that when reading them?

Cheers
 
The answer is no for most of the PROM in Pet.
The ROMs use other inputs for address decoding. When I read ROMs that are not exact replacement for I make adapters. Any pin that can have an incorrect voltage on it is disconnected. Make sure to not pass the programming voltage to the part. Look at the schematics for Pets. It will show how all the pins are used. Make sure if you are using a newer programmer that can read manufacture ID that you don't use the pin that is used to access the ID. If you run out of pins to read the entire ROM, use switches and read them a piece at a time.
Dwight
 
Dwight is probably talking about JEDEC standard EPROMs like the 2732; the TI 2532 is pretty well compatible with the 2332s used in most PETs, although not always with ones used in disk drives etc.

Oddly enough, even the 28-pin 2564 is pin-compatible with a couple of jumpers.

Here's a datasheet for the 2332 used in the PET; you should have no trouble finding one for the 2532 for comparison.

 
eight088 said:
Hi

I just got my GQ-4x4 programmer, and I'm wanting to read the roms from a pet 8032. The writing on the rom is 901465-21. Before I do, I just wanted to know what type of rom I would select in usb prg in case choosing the wrong one can damage the rom? I think 2532 roms are a replacement so can I select that when reading them?

Cheers
Click to expand...

They are for my Dynamic PET read equivalent for the 2532, so if your ROMs are the same type as my PET, you can select TMS2532JL , or just 2532 on the GQ-4x. The GQ-4x only supports reads (not writes) for the "2532 " selection anyway I believe.

It is not necessary, but I got a little paranoid about accidentally trying to write to the original ROMs by mistake and damaging them, so I made an adapter with two IC sockets to prevent that, but it is pretty unlikely if you are careful and don't select the write option in the GQ-4x software.
 
Hugo Holden said:
They are for my Dynamic PET read equivalent for the 2532, so if your ROMs are the same type as my PET, you can select TMS2532JL , or just 2532 on the GQ-4x. The GQ-4x only supports reads (not writes) for the "2532 " selection anyway I believe.

It is not necessary, but I got a little paranoid about accidentally trying to write to the original ROMs by mistake and damaging them, so I made an adapter with two IC sockets to prevent that, but it is pretty unlikely if you are careful and don't select the write option in the GQ-4x software.
Click to expand...

Some of the older Pet ROMs have partial address decoding. As Hugo says, you can use a larger address space EPROM mapping and attach the extra address decoding to addresses of the larger 27xx series parts. I still think it is best to do this with the programming voltage disconnected. I like to make adapter with three layers of machine pin sockets. It is easier to disconnect pins by punching the pin out. The middle layer is good for some of the rewiring.
Dwight
 
Just as an fyi, I was able to read the rom in two passes. I read it as a 2716 to get the first 2k, then as a 2532 to get the second 2k and merged the two contents together. Once I did this the checksum checked out as per the file on zimmers. I wasn't sure this would work, but as I thought the chip was dead I didn't mind testing the theory. The reason for thinking it was dead was because it got very hot when the machine was turned on, compared to the others.

Thanks for the replies :)
 
Gary C said:
nothing to add really but it's a shame we don't make chips as beautiful as we used to
:)
Click to expand...
Well I have to agree with you there.

IC's made of ceramic and gold appear to have become a luxury that few could afford.

So Epoxy packages started to replace them.

But if that is not all, the epoxy changed too.

The original epoxy packages that TI made in the late 1960's & late 1970's were almost as good as ceramic. Super hard resin and temperature resistant. So much so that they had to divide the IC's up in the production line with disc cutting like grinder tools. If you look at these early packages you can see the saw marks on the end. They are so temperature resistant, you cannot melt them even with a soldering iron set on 400 Deg C.

Later though, the epoxy formula changed and was softer and that is what we have today on nearly all IC's , except perhaps the occasional wide temperature range mil spec ones, which remain ceramic.

Comparing the old epoxy with the new, is like comparing a 1930's vintage 78 rpm record, with a Vinyl one from the 1970's. One is hard, brittle, temperature & wear resistant, the other soft, pliable and more easily melted.

Where I can, I try to buy ceramic cased IC's. For the 74 series I usually go for the mil spec 54 equivalents that were always ceramic.
 
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