jasa1063 wrote on 2026-01-19, 02:52:

I just picked up an AST Advantage! PRO 486SX/33. It can support 64K or 256K external cache. There are 8 DIP-28 sockets and 1 DIP-32 for tag ram. I thought I could get by with a DIP-28 32K SRAM chip for the tag ram. but that does not work. I am having difficulty locating a source for 32Xx9 DIP-32 SRAM chip. Does anyone know a good source for a one? I found this one on eBay, but I am not sure this would work. Any input would be appreciated.

https://www.ebay.com/itm/277621132195?_skw=32K+SRAM+DIP-32

Did you perhaps not insert it quite right? In most cases the DIP-32 socket is backwards compatible with a DIP-28 chip, if you leave the left 4 pins open.

The Ebay one should also work, though the picture is generic. The detail description below seems to confirm it's a NARROW DIP-32, which is what you need.
The name and description also seem inconsistent, '512' seems to say it's actually 64Kb x 8. But bigger usually works fine.

Beerfloat wrote on 2026-01-19, 04:56:

Did you perhaps not insert it quite right? In most cases the DIP-32 socket is backwards compatible with a DIP-28 chip, if you le […]
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jasa1063 wrote on 2026-01-19, 02:52:

I just picked up an AST Advantage! PRO 486SX/33. It can support 64K or 256K external cache. There are 8 DIP-28 sockets and 1 DIP-32 for tag ram. I thought I could get by with a DIP-28 32K SRAM chip for the tag ram. but that does not work. I am having difficulty locating a source for 32Xx9 DIP-32 SRAM chip. Does anyone know a good source for a one? I found this one on eBay, but I am not sure this would work. Any input would be appreciated.

https://www.ebay.com/itm/277621132195?_skw=32K+SRAM+DIP-32

Did you perhaps not insert it quite right? In most cases the DIP-32 socket is backwards compatible with a DIP-28 chip, if you leave the left 4 pins open.

The Ebay one should also work, though the picture is generic. The detail description below seems to confirm it's a NARROW DIP-32, which is what you need.
The name and description also seem inconsistent, '512' seems to say it's actually 64Kb x 8. But bigger usually works fine.

I did insert the DIP-28 cache chip in correctly and I also tested all the SRAM chips in Retro Chip Tester Pro. I will look into ordering the one from eBay.

I found some Alliance Semiconductor AS7C259-15PC 32Kx9 DIP32 15ns SRAM modules for $2.80 each with $8.00 shipping on UTSource. I bought 10, so I should be good to go!

Nice find, look forward to success story

Beerfloat wrote on 2026-01-19, 04:56:

Did you perhaps not insert it quite right? In most cases the DIP-32 socket is backwards compatible with a DIP-28 chip, if you leave the left 4 pins open.

It is true that 32k * 8 chips work fine in sockets that also accept 64k*8 and 128k*8. The pinout of the *8 chips has been extended in a way to bigger sizes that allows this kind of compatibility. This has already been done this way when stepping up from 8k*8 to 32k*8.

On the other hand, *9 chips use a different pinout. The extra data pin is at the location that is used for A0, one of the address bits, on *8 chips. So unless that pin is reconfigured using a jumper, a board that is designed for *9 chips does not work with *8 chips.

The 32Kx9 DIP32 SRAM I got from UTSource works and the computer now has a functional 256K cache. I am very happy with the result.

jasa1063 wrote on 2026-02-07, 23:17:

The 32Kx9 DIO32 SRAM I got from UTSource works and the computer now has a functional 256K cache. I am very happy with the result.

Very cool congrats!