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To the community,

I have several Myarc 512 ramdisks that have been in storage many years. I am in the process of pulling things out and making repairs. I have two, one that is set up as a memory card for a Geneve and the other still set up as a ramdisk for TI/Geneve, that are facing issues. One is completely missing the GAL16V8 and the other has a bad one, known to be bad after replacing a bad 74LS139, and a bad HM50464 ram chip and then when it wouldn't come up as extended memory on the Geneve, I switched the GAL out with the known good GAL, I had on the working 512 card and it worked.

 

I am going to research on how to dump the good one, late last night I try to read the good one in my Minipro, and all I see is a series of 1's, but the bad one has 1's till about the last 50 or so values then it has a mixture of 1's and what could be 0's, but they look like they have a little tiny numeral 5 in the center, will give screen shots tomorrow.

 

I bring the topic up because I feel it would be good to start a repository of PAL and GAL jedec files as we figure out how to dump them. Like helocast has started to do on the Corcomp controller. Things happen and I would hate to see a lot of cards laying by the way side, because they can't function due to a part that at the time can't be replaced.

 

Thoughts. Thanks,

Ricky

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Ricky,

 

I agree about a repository for the PAL and GAL files.

 

You did write something that I am not sure I misinterpreted or not, so I want to make sure we are on both the same page.

 

An unmodified Myarc 512K card will not be useable in any situation I am aware on a Geneve 9640. The only way to use a Myarc 512K card on a Geneve is to do the modification. Once a card is modified for the Geneve, it is not useable on the TI-99/4A. The 512K card can be used for either the TI-99/4A if the card is not modified, or in a modified form, for the Geneve. You can't move the same card between the two systems.

 

Your message seemed to suggest one card was setup for both, and to my knowledge, that was never possible.

Beery

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Ricky,

 

I agree about a repository for the PAL and GAL files.

 

You did write something that I am not sure I misinterpreted or not, so I want to make sure we are on both the same page.

 

An unmodified Myarc 512K card will not be useable in any situation I am aware on a Geneve 9640. The only way to use a Myarc 512K card on a Geneve is to do the modification. Once a card is modified for the Geneve, it is not useable on the TI-99/4A. The 512K card can be used for either the TI-99/4A if the card is not modified, or in a modified form, for the Geneve. You can't move the same card between the two systems.

 

Your message seemed to suggest one card was setup for both, and to my knowledge, that was never possible.

Beery

You would be right, but of the Myarc cards, I have at hand, I use two with the Geneve, and are modified, I used the eproms in two Foundation cards, converting them to Myarc compatible at the same time, I did it BITD, the other Myarc 512 card is not modified, but was missing the eprom, GAL, and the 74HCT259 chip setting above it, but they all use the same GAL, the one close to the crystal on the lower left hand corner. I think I have another one or two in storage, but have not found them yet. Sorry if there was any misunderstanding, that's just my thought processes I guess. :-D The two chips missing together, leads me to conclude that I still have that GAL somewhere and it was knocked off in storage.

Edited by RickyDean

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Jim Fetzner and I have been discussing the possibility of establishing a PAL/GAL repository for JEDEC files for a couple of years. The problem is that Myarc and most CorComp cards have the PALs locked which means that they cannot be easily read. The only recourse is to reverse engineer the circuitry to reconstitute the equations to produce appropriate JEDEC files. Anyone in the mood to take on such a project? I think Jim has the JEDEC files for most of the TI cards.

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Jim Fetzner and I have been discussing the possibility of establishing a PAL/GAL repository for JEDEC files for a couple of years. The problem is that Myarc and most CorComp cards have the PALs locked which means that they cannot be easily read. The only recourse is to reverse engineer the circuitry to reconstitute the equations to produce appropriate JEDEC files. Anyone in the mood to take on such a project? I think Jim has the JEDEC files for most of the TI cards.

I know that helocast has done some work in this area, but I am going to build a pal/gal dumper for common chips, found on the internet and see what I can accomplish. Stuart has stated to me too, that his 9900 board could also possibly be used in this type of work also. But I am not versed in Assembly Language, so this would be difficult for me, but not impossible.

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If the PAL/GAL equations can be re-constructed, one could use WINCUPL or another similar utility to assemble the JEDEC files from them. I have the logic files for the CorCom FDC Rev A and some miscellaneous third-party PALs (i.e., QUEST RAMdisk).

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Do you by chance have the logic files for the Databiotics Grand RAM? I have some experience with wincupl and i'm willing to figure out how to write the new PAL chip. But i'm not advanced enough yet to work out my own reverse engineered logic.

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What would also be useful is for a list of the PAL types used on the various boards, and whether there is a pin-for-pin GAL replacement. Most modern (EPROM) programmers can program GALs, but very few (if any) can program PALs. For the CorComp FDC, it looks like a small adapter board will be needed to use GALs in place of the 12L6 PALs; using PALs directly (if you were able to program them) could get rather expensive if it takes several iterations to get the correct equations.

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What would also be useful is for a list of the PAL types used on the various boards, and whether there is a pin-for-pin GAL replacement. Most modern (EPROM) programmers can program GALs, but very few (if any) can program PALs. For the CorComp FDC, it looks like a small adapter board will be needed to use GALs in place of the 12L6 PALs; using PALs directly (if you were able to program them) could get rather expensive if it takes several iterations to get the correct equations.

 

Ah, looks like I was wrong. A GAL16V8 can directly replace a PAL 12L6. ;-)

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This is a somewhat kool looking item that found it's way to me through the generosity of another AA member.

post-64523-0-85843200-1553799747.jpg

Is this where I come to figure out what type of file (if available)... would be used and what kind of programmer might allow me to consider there to be good reason for populating this "Universe"? :)

I think this originaly used PALs but could now use GALs...

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This is a somewhat kool looking item that found it's way to me through the generosity of another AA member.

 

attachicon.gifWHTbd.JPG

 

Is this where I come to figure out what type of file (if available)... would be used and what kind of programmer might allow me to consider there to be good reason for populating this "Universe"? :)

 

I think this originaly used PALs but could now use GALs...

You can probably use the TL866 minipro programmer to program this. I know it will allow access to the Gal16v8, don't know about the PAL's. But you will need to find the jedec files to burn these, the original developer should have them, but others here may have too. I'm sure others here will have a better run down on what you need.

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So far as I know, no one in the community has the JEDEC files for those cartridge boards. A few of the bare boards turned up at the Chicago Faire a few years ago, and have trickled out into the community in the time since. The PALs would be doing the GROM chip selection and the ROM chip banking, as the four 161s on the board would be doing the address stepping for the GROMs.

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One of the problems with those boards was that the PAL equations were incorrect. As a result, the board was non-functional. Also, I believe there was a design flaw.

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