those seem to be SRAM chips, so a cache module most likely.

Could this be an Intel Turbo Cache module? That was a thing in early 486 (mainly OEM) era.

That said, iirc Turbo Cache was taller and narrower. This looks like it might have been for use in a laptop.

Edit:
Nope, not turbo cache, those things had a 485 cache controller on them too

Those chips are IDT 71256SA15Y - 32Kx8 with a speedy 15ns access time. So yeah, my guess is that it's a 256KB L2 cache module (plus a couple extra chips for the cache tags) for an 80486 motherboard.

Proprietary graphics card memory upgrade?

Gemini AI tells me this is

This board is a high-speed SRAM memory expansion module manufactured in 1995 for industrial telecommunications equipment, specifically for Nokia's DX200 digital switching systems. The presence of ten IDT 71256 chips confirms a total capacity of 320 KB (32 KB per chip), where the extra two chips likely handled parity bits or error correction, which was a standard requirement for mission-critical infrastructure. The "15Y" suffix indicates a very fast 15-nanosecond access time, while the 54-pin connectors and the "M" in a circle logo identify it as a proprietary "mezzanine" card built on a PCB from the Finnish manufacturer M-Sercap Oy (Aspocomp).
Technically, the board functions as a high-performance data buffer or routing table storage. The two 74F373D transparent latches and the 74F125 buffer act as bus interfaces, managing the flow of data between the memory chips and the main processor unit. The date codes on the components and stickers (9414 and 9522) pinpoint its production to mid-1995. Given its rugged design, including high-quality tantalum capacitors and gold-plated connectors, this board was engineered for 24/7 reliability in the backbone of early GSM mobile networks.

leency wrote on 2026-05-14, 08:47:

Gemini AI tells me

to eat glue ...

leency wrote on 2026-05-14, 08:47:

specifically for Nokia's DX200 digital switching systems

Manufactured since seventies ...

leency wrote on 2026-05-14, 08:47:

"M" in a circle logo identify it as a proprietary "mezzanine" card built on a PCB from the Finnish manufacturer M-Sercap Oy

founded in 2009

leency wrote on 2026-05-14, 08:47:

(Aspocomp).

unrelated to Sercap, never used that logo

its glue all the way down

As they say best way to get good answer is to post wrong one :] Those cards are Cache modules for https://theretroweb.com/motherboards/s/icl-er … -c4-d4-p-series Re: Need help identifying extra socket on 486 SX and posible upgrades.
edit: also https://theretroweb.com/motherboards/s/icl-er … 0,-ergopro-e440
On paper British ICL (owned almost entirely by Japanese Fujitsu at the time) bought Nokia Data in 1991. https://www.latimes.com/archives/la-xpm-1991- … -254-story.html First they made ICL branded computers in Finland, then used Fujitsu name.

@rasz_pl, you've made my day! A"I" chat/search bots equal sh33t!

Those PCs are so obscure I might even be inclined to design reproduction cache if an owned of one of those ICL
ERGOPROs shows up.

aVd wrote on 2026-05-14, 10:15:

@rasz_pl, you've made my day! A"I" chat/search bots equal sh33t!

They have their moments. This one did correctly guess Finland and smelled Nokia. Probably slurped up pictures of Nokia equipment with same PCB manufacturing house logo.

Can see same logo and even PRI-SIDE SEC-SIDE text on this mobo https://theretroweb.com/motherboards/s/icl-er … 0,-ergopro-e440

leency wrote on 2026-05-14, 08:47:

Gemini AI tells me this is

This board is a high-speed SRAM memory expansion module manufactured in 1995 for industrial telecommunications equipment, specifically for Nokia's DX200 digital switching systems. The presence of ten IDT 71256 chips confirms a total capacity of 320 KB (32 KB per chip), where the extra two chips likely handled parity bits or error correction, which was a standard requirement for mission-critical infrastructure. The "15Y" suffix indicates a very fast 15-nanosecond access time, while the 54-pin connectors and the "M" in a circle logo identify it as a proprietary "mezzanine" card built on a PCB from the Finnish manufacturer M-Sercap Oy (Aspocomp).
Technically, the board functions as a high-performance data buffer or routing table storage. The two 74F373D transparent latches and the 74F125 buffer act as bus interfaces, managing the flow of data between the memory chips and the main processor unit. The date codes on the components and stickers (9414 and 9522) pinpoint its production to mid-1995. Given its rugged design, including high-quality tantalum capacitors and gold-plated connectors, this board was engineered for 24/7 reliability in the backbone of early GSM mobile networks.

Perhaps it fits on this board:
Re: Need help identifying extra socket on 486 SX and posible upgrades.

Kasreyn wrote on 2021-07-16, 18:32:

I also have one of these ICL Ergo Pro C4/33 slimline computers, and no, there was never a cache module installed. Bit of a sham […]
Show full quote

I also have one of these ICL Ergo Pro C4/33 slimline computers, and no, there was never a cache module installed.
Bit of a shame since it could be a nice upgrade path with a DX2 66 MHz.

This is it:

What? ICL made proprietary PC’s. Where does Nokia come from?

These confidently wrong hallucinations…

rasz_pl wrote on 2026-05-14, 10:03:

leency wrote on 2026-05-14, 08:47:

Gemini AI tells me

to eat glue ...

Wasn’t it rocks?

The glue is to stick the cheese to the pizza.

Ok, in the end I guess you’d eat that roo…

st31276a wrote on 2026-05-14, 10:50:

What? ICL made proprietary PC’s. Where does Nokia come from?

ICL made normal PCs since nineties in former Nokia Finnish factory.

Ah that's nice we have solved this puzzle. Thanks!
I remember I found it in a bin of 8086-486 components intended for recycling.

I can sell this card or even donate in case of scintific / replication purpose.