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Nes CHR RAM/SRAM Question
http://forums.nesdev.com/viewtopic.php?f=28&t=16182
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Author:  silentadminz [ Thu Jul 06, 2017 6:42 pm ]
Post subject:  Nes CHR RAM/SRAM Question

My question is what other options for chr ram do I have, is there a list somewhere of compatibility or what should I be comparing besides it being Sram @ 8192x8, DIP28, pinout, and physical form factor of the ram. Looking for an exact drop in replacement, not rewiring of the pins to the board. I assume it can be bigger in memory size (more than 8x8), but not sure hense the post.

HM6264LP-15 - Currently have a few of these and they work great for UN/OROM..etc Looking at HY6264ALP-70 datasheet it looks to be compatible? I'm no expert in ram or indepth electronics, just making a private repro collection/hobby and need to find cheaper ram solutions preferably in bulk that doesn't cost $243k. :?:

Author:  Memblers [ Thu Jul 06, 2017 8:26 pm ]
Post subject:  Re: Nes CHR RAM/SRAM Question

Yeah, HM6264 and HY6264 are compatible. Any part with 6264 in the part number should be the same.

62256 (32k x 8) is more common (in DIP28 package, I'm not so sure though) and is almost pin-compatible. You would need to make sure pin 1 is connected to something (could be 5V, GND, or even pin 2). Pin 26 is different, more than likely whatever board you're using has pin 26 connected to 5V. In that case, no further changes are needed.

Author:  silentadminz [ Fri Jul 07, 2017 12:57 am ]
Post subject:  Re: Nes CHR RAM/SRAM Question

Memblers wrote:
Yeah, HM6264 and HY6264 are compatible. Any part with 6264 in the part number should be the same.

62256 (32k x 8) is more common (in DIP28 package, I'm not so sure though) and is almost pin-compatible. You would need to make sure pin 1 is connected to something (could be 5V, GND, or even pin 2). Pin 26 is different, more than likely whatever board you're using has pin 26 connected to 5V. In that case, no further changes are needed.


Awesome, Appreciate the info. I figured the 6264 series was compatible, but needed the verbal thumbs up from someone that knows so things :D I looked up HM62256BLP-7 is a DIP28 a good bit cheaper too, the pinout does look different though as said. I'll steer clear of of that for now, but it's nice to know there are options.

Author:  tepples [ Fri Jul 07, 2017 6:19 am ]
Post subject:  Re: Nes CHR RAM/SRAM Question

The 62256 is the same thing as a 6264, just with 32K instead of 8K and no +CE. This can give you bankable CHR RAM, which has advantages.

Author:  silentadminz [ Fri Jul 07, 2017 7:43 am ]
Post subject:  Re: Nes CHR RAM/SRAM Question

tepples wrote:
The 62256 is the same thing as a 6264, just with 32K instead of 8K and no +CE. This can give you bankable CHR RAM, which has advantages.


Will there be any issues with roms/nes seeing more ram on the cart or no :?: From what was said above "make sure pin 1 is connected to something (could be 5V, GND, or even pin 2) and ping 26 should be fine if already connected to 5v. Would I just lift pin one and connect it to one of the previous mentioned or just leave it down and jump it over to one of those mentioned?

I already bought a bulk of 6264's :beer: so I probably won't need any for a good while, but I could have saved $20 perhaps :roll:

Author:  tokumaru [ Fri Jul 07, 2017 9:23 am ]
Post subject:  Re: Nes CHR RAM/SRAM Question

By connecting the (unneeded) higher address lines to GND or 5V you are making the extra memory in the chip inaccessible, the NES will not be able to tell the difference from an 8KB chip.

Bankable CHR-RAM would only benefit new programs made to work with the banking scheme you design.

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