Unknown EPROM

[centrespot]

Can anyone shed some light on what this eprom would be used for, it was inside a Commodore PET 4032, unfortunately the computer didn't come with any history when I bought it several decades ago.

[nlpe1goo]

Hi,
It depends on what you want to know. I can tell you only that it is a 4K*8 bits UV erasable EPROM. You probably found out by yourself. If you have a prom programmer you could read the eprom and get the data. Unfortunately I have no knowledge of the PET-computer itself.
Perhaps telling the location of that prom in your PET would help the others who know more about this computer.

[SiriusHardware]

Colin is probably going to be the go-to-guy for this, but it is probably an application / utility EPROM which is not essential for the working of the machine but provides some extra functionality when fitted.

Read it out with an EPROM reader / programmer (bear in mind that it is a 2532, not a 2732 - the pinout is different) and see if there is any plain text in the EPROM which may include the name of the application / name of the author etc and also, any text which is intended to be displayed as menu text may give you some clue as to what it does.

When you do read it, look at what your reader says the 16-bit checksum of the code read out from it is - with any luck it will be 8050 hex, the 4-digit number written on the label.

[Qbertni]

Visicalc on the pet came with a rom which acted as copy protection, this might be for that purpose

[SiriusHardware]

'VC' sounds highly suggestive in that context doesn't it?

But if so then the content of the EPROM is likely to be deliberately obscure. It may even be that each individual disc copy of Visicalc went out with a unique matching EPROM which means that unfortunately, even if you found a copy of PET Visicalc on disc it would be unlikely to run with this particular EPROM.

The EPROM looks home-made though so maybe there were widespread copies of the disc which matched this particular 'licence key' EPROM doing the rounds back in the day.

[ScottishColin]

If you don't have an EPROM reader, I can take a look if you're prepared to post it to me.

I believe VisiCalc EPROMs were individual per user, but as Sirius says, it's possible that someone might have either copied the EPROM and diskette as a pair.

The 8050 marking is interesting seeing as you have just fixed one of them. Perhaps it's related to that or maybe it's the checksum.

Anyway - let's see what's on the EPROM.

Colin.

[centrespot]

I did already have a go at reading the eprom and it didn't show much, only real text is as per attached photo.
I will sort through my disks to see if there is a visicalc one

[centrespot]

Unfortunately no disk

[centrespot]

I've googled and found the files for visicalc here

https://www.zimmers.net/anonftp/pub/cbm/pet/ALLFILES.html

I'm a bit too old to understand the new ways of handling files, what is the step by step process to opening the files, for example this one which has a copy of the ROM image

visicalc40-80+rom.d64.gz

[SiriusHardware]

8050 doesn't seem to be the checksum so maybe it's the 'Licence Key' number which maybe matched a similar number on its disc.

A '.gz' file is an 'archive' file similar to a .zip file. If you have a Linux based computer, even a Raspberry Pi, saving the file onto that and then double clicking on that file would bring up an option to unpack and separate the individual files in the archive. I've just checked and my works Win10 computer here has no idea what to do with a .gz file unfortunately so I can't just unpack the files and post them for you.

The good news is that that archive surely must contain a 'matched' Visicalc program file and ROM file otherwise there would be little point in archiving it.

[centrespot]

Originally Posted by SiriusHardware

8050 doesn't seem to be the checksum so maybe it's the 'Licence Key' number which maybe matched a similar number on its disc.

A '.gz' file is an 'archive' file similar to a .zip file. If you have a Linux based computer, even a Raspberry Pi, saving the file onto that and then double clicking on that file would bring up an option to unpack and separate the individual files in the archive.

The good news is that that archive surely must contain a 'matched' Visicalc program file and ROM file otherwise there would be little point in archiving it.

Sadly only windows based computers, would someone else be able to unpack it and somehow send it to me or have a link to download it

[ScottishColin]

With reference to the text found, see page 13 of the attached PDF. Too much of a coincidence for me. I have a 3022 and I'll pull the EPROM from there and compare it.

Would you mind uploading the contents of your EPROM as an attachment here?

https://retro-bobbel.de/zimmers/cbm/manuals/printers/Druckerhandbuch_cbm_3022_3023.pdf

Also, on a Windows PC if you download and install 7-ZIP it will allow you to unpack .gz files. .

Colin.

[ScottishColin]

So you need to install 7-Zip (or your preferred .gz program) on windows and unpack the .gz file

Then you need a program that understands .d64 files - I use DirMaster here:

https://style64.org/dirmaster

Attached is a screenshot of the files contained in the .d64 file.

I also attach the file you have posted in post 9 as a .ZIP file in case you don't want to install 7-ZIP.

This still may turn out to be a Visicalc EPROM - we're not done yet I don't think.

There are Visicalc EPROM images here that you might like to download and compare against the one you have:

https://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/other/index.html

Colin.

[ScottishColin]

OK - I'll stand down on the 3022 EPROM.

The following file:

https://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/other/visicalc-9000.901472-04.bin

Seems to have the same text and checksum as the picture you posted in post 7.

If you could upload the .bin you have extracted we can confirm (or you can download the file in this post and compare yourself).

Colin.

[centrespot]

Originally Posted by ScottishColin

Would you mind uploading the contents of your EPROM as an attachment here?

zipped .bin file attached

[centrespot]

Definately the visical ROM

[centrespot]

Originally Posted by ScottishColin

So you need to install 7-Zip (or your preferred .gz program) on windows and unpack the .gz file

Then you need a program that understands .d64 files - I use DirMaster here:

https://style64.org/dirmaster

Attached is a screenshot of the files contained in the .d64 file.

I also attach the file you have posted in post 9 as a .ZIP file in case you don't want to install 7-ZIP.

This still may turn out to be a Visicalc EPROM - we're not done yet I don't think.

There are Visicalc EPROM images here that you might like to download and compare against the one you have:

https://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/other/index.html

Colin.

Thank you Colin
Presumably once this is done (which I have) the result needs to be saved to a 5.25 disk in some way.

[ScottishColin]

I wonder why it had 8050 written on it.

I do recall that some programs (I can't say that this is the case for VisiCalc) were supplied on both 'notmal' and high density diskettes. I wonder if this was that. Who knows.

Now you need to get VisiCalc running....

There's some help here if it isn't easy:

https://abitoutofplace.wordpress.com/2015/04/30/visicalc-on-a-pet-8032/

Colin.

[SiriusHardware]

I think you might need one of the PET SD CARD 'drive' units so you can put the files from a PC onto an SD card and copy them onto a real PET disc.

If you go that route then you specifically need an SD card 'drive unit' which can be connected to the machine at the same time as the real drives - not all of them have that connectivity.

Again, Colin is your man for the lowdown on this sort of thing. He did a roundup of all the after market gizmos for the PET just recently elsewhere in this section.

[centrespot]

Originally Posted by SiriusHardware

I think you might need one of the PET SD CARD 'drive' units so you can put the files from a PC onto an SD card and copy them onto a real PET disc.

If you go that route then you specifically need an SD card 'drive unit' which can be connected to the machine at the same time as the real drives - not all of them have that connectivity.

Again, Colin is your man for the lowdown on this sort of thing. He did a roundup of all the after market gizmos for the PET just recently elsewhere in this section.

I had placed an order with bitfixer.com on 10th Jan for the PETdisk MAX v2 Kit, it has wifi capability as well, I'm hoping it will arrive soon and give me the ability to create real disks as well as loading from the SD card.