Probably SOJ chips.

Found a bunch on eBay, thanks for the pointer!

Never seen this socketed cache before until I picked up an IBM PC330-P75 that also had them. If needed I can look up the exact chip types - but it's SOJ alright.

WIthout having any manual for this machine, could you tell me what chips you're using?

This one seems to mean to me that 128k is found in each chip, and I will need 8 of them, for a total of 1,024 (seems excessive)

https://www.ebay.ca/itm/QTY-20-TC558128AJ-20- … AwAAOSwPCVX3Aee

but I would really like to go 256k.

Is this what I need?

https://www.ebay.ca/itm/5PCS-IDT71256SA25Y-71 … HEAAOSwcmZa5Y48

I have a Socket 5 motherboard using SRAM chips in SOJ-28 package. Sockets are 32-pin and chips are inserted leaving out pins 1,2,31,32, as usually seen on 486 motherboards. Looked up their datasheets and I think they are 3.3V SRAM. Never got to test that motherboard, I think all my power supplies lack the dedicated 3.3v/6-pin connector. Lazy, I know 😁

Hey quicknick! 😁

Upon closer inspection (the previous pic was from the seller), it clearly says 32kx8 on the board, in two banks. The jumpers are also labelled very well. I really like the attention to detail in this machine! All the cache sockets are 28 pin, but the TAG chip is a 32 pin SOJ.

I think I'll get the 32kx8 units off eBay, but I'm not sure about the tag. Now that I have a spec sheet for the product number, I will take a multimeter to the TAG socket and see what/where the voltage comes out of, and compare it to the spec sheet.

So far so good, I transplanted all the goodies out of my clone 486/66 (hard disk, CDROM, NIC, sound, video, and CF, as well as replaced the BIOS battery). I also paired it with my NCR 17 inch CRT which is looking a bit worn, in need of a power button cover, and generally some retrobrighting.

Here it is:

It's pretty tightly packed in there, but I appreciate the German 90s build quality.

What I still need to do:

-CACHE!
-5.25 inch floppy
-CPU fan
-Solder on a small 3.5 inch floppy power connector for my CF card reader
-Obtain a Microsoft PS/2 mouse
-Load DOS/Win LAN drivers

A fall/winter project for sure.

Tag RAM requires a 32kx9 chip, CY7C188 for example

Thank you all! That was the final piece of the puzzle. I purchased a 20NS 32 pin TAG chip, now we wait for the international shipments to arrive at my door and the upgrade can begin! For now, cache-less Civ2 play...

Also, holy crap - https://www.ebay.com/itm/SIEMENS-NIXDORF-PCD- … G-/181406916333 😕

Also also : Re: 486 Upgrade - is it worth it?

Could have saved $6, contributed to the British economy, and not have to wait 45 days for the cache to arrive. I should always search Vogons first. Let that be a $6 lesson to me.

Jed118 wrote:

WIthout having any manual for this machine, could you tell me what chips you're using?

Apologies for the late reply, but at last found time to open up my PC330 today.

Cache chip: Motorola MCM6306DJ15B (32kx8 3V 15ns fast SRAM)
Tag: ST M628032-15E1 (also 32kx8 3V 15ns SRAM)

Interesting: the sockets for the cache chips are 32p sockets, but the chips are 28p, so they don't use the last pins. The tag socket is 28p and fits snugly.

I've seen this technique used on DIP type cache chips. Hell, I've even seen offset BIOS chips.

It seems that your chips are 3.3v, whereas from what I gather mine need to be 5v. Thanks for digging that up though, I might actually have a use for the 3.3v chips as I just came across something interesting.

Cache memory came really quickly!! The tag chip (from the US) came at the same time as the chips from China.

And has been added!! Set a couple jumpers...

This is very satisfying:

Now to activate it in BIOS:

Boot it up,

And some benchmarking (higher scores = cache)

And while I was underhood, I added a very fast CPU cooler, and since I had to wire it in, I soldered on an extra molex for my CF card. However since it is a WD disk (I have had issues with these and CF cards on the same channel), it won't play nice with it. Looks like I will need to find a 1-2gb disk somewhere...

Jed118 wrote:

And while I was underhood, I added a very fast CPU cooler, ...

Oh man, that looks like one of those ~9K RPM 1U server 40mm fans... is it as loud as I think it is? At least the CPU and new cache will be cold at all times with it on. 🤣

Jed118 wrote:

I've seen this technique used on DIP type cache chips. Hell, I've even seen offset BIOS chips.

It seems that your chips are 3.3v, whereas from what I gather mine need to be 5v. Thanks for digging that up though, I might actually have a use for the 3.3v chips as I just came across something interesting.

Those voltages make sense with 486 vs Pentium P54C, hadn't considered it, but it's the different I/O voltage of course.

SW-SSG wrote:

Jed118 wrote:

And while I was underhood, I added a very fast CPU cooler, ...

Oh man, that looks like one of those ~9K RPM 1U server 40mm fans... is it as loud as I think it is? At least the CPU and new cache will be cold at all times with it on. 🤣

Yeah, there's a steady sound of very fast air movement. I picked up two of these, the other one is on my 233 MMX machine. They're nice if you don't mind the, I'm not sure what to call it, it's not really a hum or and not quite a whistle, closest I can think of is a carburetor on fast idle without the air cleaner on it minus the engine noise.

hey jed118, could you give me the product number of the sram and tag cache ? I have the same board without the cache memory and would like to fill it as you did. The markings are unreadable on the photo.
Thank you

Guys, all of them will work ? Cheaper memory cache is even faster.