4264 vs. 2164 RAM chips

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PunkTiger
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4264 vs. 2164 RAM chips

Post by PunkTiger »

My venerable breadbin C64 has developed a black screen problem. (Sounds familiar, right?) Dead test cartridge gives me one flash telling me the first (hopefully, only) fault is the memory chip in U12. Pop open the computer, expecting to find some 4264 chips... instead I find 8 Sharp KM2164 chips soldered on the board (see pic). :shock: Well, THAT'S new (the chips, not the soldering). An online search for info on the 2164 chip yields nothing (aside from some Ram truck parts, depending on the search criteria).

So, I ask for wisdom and guidance from those who may be more experienced: can the 4264 chips be a direct replacement for the 2164 chips, or are there differences I should know about? I know it would probably be a Bad Idea to mix the chips in any case, so I'll probably have to buy a complete set of 8 to repair good ol' Vyvyan, and I want to make sure the pinouts of the chips are compatible.

Thanks for any help you can give me.
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radron5809
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Re: 4264 vs. 2164 RAM chips

Post by radron5809 »

I snipped this from the 1986 Sharp-Mos semiconductor data book, don't know if it will help or not. By the way, you aren't using a stock c64 power supply are you? If so, get away from it, they kill before they die. Think they take out the RAM chips first.
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Re: 4264 vs. 2164 RAM chips

Post by radron5809 »

Another snip
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Re: 4264 vs. 2164 RAM chips

Post by PunkTiger »

radron5809 wrote:
Sat May 18, 2019 3:44 pm
I snipped this from the 1986 Sharp-Mos semiconductor data book, don't know if it will help or not. By the way, you aren't using a stock c64 power supply are you? If so, get away from it, they kill before they die. Think they take out the RAM chips first.
Thanks for the info. I guess more research is necessary. And no, I'm not using the stock power supply. I'll be getting a modern supply in the near future, but for now, I cobbled together a ghetto power supply: a 9VAC wall wart, and a 5VDC wall wart (appropriate amperages for them both) going into a DIN plug. Crude, but effective.

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Re: 4264 vs. 2164 RAM chips

Post by radron5809 »

I read this in the Melon64 forum in the past. I ordered these chips from digikey but never used any yet, just in case I need them. Believe you can use them to replace bad C64 chips.
eslapion wrote:
Sun Jan 24, 2016 11:38 pm
Zippy Zapp wrote:Is there a list someplace that shows modern equivalents? I thought the important parts was 74LS257, etc. And that the other letters like SN for TI and BN for package type etc didn't matter. But apparently it does.
The extra letters are sometimes used to indicate the fabrication process (who cares...) and the type of package which can be surface mount SOIC, TSSOP or normal through hole DIP.

Obviously you want a through hole component no matter what letter is used.

Honestly, I just search on Digikey for 74LSxxx and then in the search options, I check "In stock" and click on "through hole" in the "mounting type" options field.

Usually what remains is the purchasing format which is either "tape and reel" in thousands of units or tubes which can contain 1 to 20 units.

I just did it on Digikey for the LS257 and the only result of this search was SN74LS257BN. At that point, whatever the letters are is insignificant.
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Re: 4264 vs. 2164 RAM chips

Post by Zippy Zapp »

Heh. As you can see above this was and still can be confusing with all these numbers etc. I have learned/relearned a lot since then. I have a cross reference for these numbers someplace but I will have to dig for it. But the 2164s are obviously compatible with the 4164s. The service manual lists them as 4164 200ns. So anything 200ns or better should be fine. You can just use a 4164 as they are still easy to come by. Actually with a bit of wire jumping to the chip you can apparently also use a 41256 which are even easier to come by, although I have not tried this myself.

https://www.c64-wiki.com/wiki/RAM

As for mixing chips it is not usually a problem. We even mixed chips back in the day when we were upgrading the 1764 REU to 512k. I still have and use the very same unit. I also upgraded quite a few other REUs at the time and the local supplier never had exactly the same brand DRAM but always something equivalent.

Jameco sells them new:
https://www.jameco.com/z/4164-150-Major ... 41662.html
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Re: 4264 vs. 2164 RAM chips

Post by eslapion »

Just wanted all of you guys to know... since sourcing dynamic RAM of 64kx1 and 64kx4 (as used on C64 and C64c boards) is becoming increasingly difficult, Francis Bernier has come up with a nice little board which allows using a pair of 32kx8 static RAM chips on C64/C64c mainboards. These ICs are still in production.

He was at the recent VCF selling his stuff and some of my products.
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Re: 4264 vs. 2164 RAM chips

Post by Zippy Zapp »

I think I read someplace that someone created a adapter board that converts a SMD DRAM that is also apparently still in production. I can't for the life of me find it but maybe someone else has heard about it.

Does using SRAM change any behavior or present any kind of compatibility problem with the 64?
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Re: 4264 vs. 2164 RAM chips

Post by Gyro Gearloose »

Hmmm, forgive my intrusion upon this learned discussion, but I think you can just pop in a 41256 chip in lieu of a 4164 and it should work as a 64k chip. The C64 will simply never address the extra memory.
The extra A8 line on the 41256 would be left floating, so you'd need to tie it to a low-impedance logic level, just strap a wire across to pin 16.
Anyone ever try this?
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Re: 4264 vs. 2164 RAM chips

Post by rmzalbar »

Zippy Zapp wrote:
Wed Jun 05, 2019 6:09 pm
Does using SRAM change any behavior or present any kind of compatibility problem with the 64?
Yeah, it does. It fixes the VSP "bug," in case your C64 is affected by it (usually C64C models, not breadbins) which is certainly not a problem.

If you're not aware of VSP, it's an intentional violation of DRAM timing to allow for a high-quality scrolling effect that the C64 shouldn't be able to do on paper. Most C64s have no trouble with it, but a few of them crash. Apparently these are most likely to be C64Cs, these use different DRAM than the breadbins. The SRAM has no trouble with it.

VSP is seen in a lot of scene demos, and increasingly used in C64 retro games. Super Mario Bros. 64 for example. I use "retro" in the sense that these are modern games but written for old hardware..

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