Interest for a C64c (250469) PLA replacement?

fordav1 said:

Anyway, I'm sure you have not sought help from the manufacturers so that's still an opportunity to solve the problem.

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Give my regards to Xilinx and tell them I need a custom version of the XC95288XL which fits on a 12x12mm footprint. I'm sure they'll be very happy to make one for less than half a million dollars.

Of course then you'll have to ask yourself where exactly are you going to storage the tens of thousands of ICs they just made for you as a minimum order for that custom version of the chip...

In the interim, while you're busy figuring how to make money out of this rather expensive venture, I'll be busy working on things which actually bring in a bit of money.

Even at $5 each it is wasted money because it is 35+ years old and will die the same way as all the others.

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Have you ever heard of the difference between the 8521 and the 6526. Also, do you know why some 6526 have the code 216A stamped on them ?

Added edit:
My 2 cents worth...

I don't recall mentioning anything about any manufacturer making a special custom chip. Hmmm let me check previous posts... hmmm, nope, nothing there about making a custom IC.
As for the last part, I'm sure everyone with a C64 is interested to know the answers to your quick quiz and why CIAnide isn't available....

fordav1 said:

I don't recall mentioning anything about any manufacturer making a special custom chip. Hmmm let me check previous posts... hmmm, nope, nothing there about making a custom IC.

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Then exactly what help did you expect me to seek from manufacturers? :jester:

They don't make any CPLDs with more than 200 macrocells of less than 20x20mm in size (a footprint of 22x22mm with the pins). Unless, of course, you come up once more with some magical solution which actually is another dead-end.:banghead:

As for the last part, I'm sure everyone with a C64 is interested to know the answers to your quick quiz and why CIAnide isn't available....

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Now, that is definitely in the previous posts...

My answer to any and all further posts you may have about this subject: :tired:

I don't know about others but this was very informative and interesting read for me, and I don't mind if it escalated a bit. Thank you eslapion, you certainly know your stuff.

b00mer said:

... Thank you eslapion, you certainly know your stuff.

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Thanks for the vote of confidence. It always makes me feel somewhat awkward when people make comments like that because I feel I don't know my stuff that much.

I can tell you for sure Gideon Zweijtzer knows his stuff a LOT more than I do.

It's funny that learning the insides of the VIC-20 and the C64 is what got me into EE and even today, 35 years later, I still learn more stuff about these machines.

If VIC-20s/C64 were still being made, I guess they would remain a good starting point and tool to learn the most important aspects of EE.

One of the most difficult aspect of making a replacement PLA for the C64c is finding pin headers with 0.070" (1.778mm) pitch. Well, I did find some which are considerably less expensive than the ones found on Digikey.

The project is still 'in the air'...

Hello, my first post

Looks like I'm reviving this thread from the dead, but I think it would be worth while to create a PLA replacement fro C64c.

I've checked the C64 service manual from 1992 edition, and they didn't cover Rev.B boards with PLA 252535-1.

Do you have any idea what would it take to make an interchangable PLA where you could "attach" RAM as there is plenty of space where RAM chip sits in Rev.4 boards, or a board with headers for RAM chip for Rev.4, and no pin headers for Rev.B ?

donnied said:

Hello, my first post

Looks like I'm reviving this thread from the dead, but I think it would be worth while to create a PLA replacement fro C64c.

I've checked the C64 service manual from 1992 edition, and they didn't cover Rev.B boards with PLA 252535-1.

Do you have any idea what would it take to make an interchangable PLA where you could "attach" RAM as there is plenty of space where RAM chip sits in Rev.4 boards, or a board with headers for RAM chip for Rev.4, and no pin headers for Rev.B ?

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The C64c mainboard I have is 250469 with PCB 252311 Rev. 3 and I invested absolutely no effort in comparing with other boards.

I truly concentrated my efforts on PLA 251715-01 and understanding exactly how it functions. So far, these efforts have not borne fruit. I'm just left with a pair of boards, one small and using surface mount and one large with DIP ICs, which are totally non functional with no explanation whatsoever.

Since the PLA 252535-01 is the 251715-01 with added color RAM then obviously I'm not there at all.

Precisely the point on what you are saying, as if 251715 can be recreated, a version of the board could be created with configurable ram, or with the header that would fit the ram socket on rev3/4, or witout header for 252535-1. RevB board has a diode on one Video RAM trace between PLA and VIC2.

As you have already done it with PLAnkton, "only" support chips integrated in one of those "super PLAs" should be added recreated...but you are the expert here

I'll be recapping both boards, and then making the Rev4 ZIF socketed when I got some time, and later the same for RevB.

Here are my boards:


Seems that someone has already done some groundwork here:

http://www.frank-buss.de/c64/pla/
http://skoe.de/docs/c64-dissected/pla/c64_pla_dissected_a4ss.pdf
http://www.zimmers.net/anonftp/pub/cbm/documents/projects/memory/c64/index.html


Source Code: https://github.com/FrankBuss/c64pla