My Moondog whitebox 486 DX4 has one of those M912s with a real Cache on it that works.

Typically the way to tell is if the chips are socketed or not, and to see if the cache traces on the motherboard lead to other components, or if they just loop back into themselves. I also have a (dead) Pc Chips M919 with fake Cache and the propreitary Cache module slot on it. the Cache on that one loops around back into the plastic chips, which say "Write Back Cache" on them (lol).

My Moondog is a pretty decent machine, not as fast as the FIC 486-PVT my main DX4 has, but it does great for what it is.

creepingnet wrote on 2022-01-11, 22:34:

My Moondog whitebox 486 DX4 has one of those M912s with a real Cache on it that works.

Typically the way to tell is if the chips are socketed or not, and to see if the cache traces on the motherboard lead to other components, or if they just loop back into themselves. I also have a (dead) Pc Chips M919 with fake Cache and the propreitary Cache module slot on it. the Cache on that one loops around back into the plastic chips, which say "Write Back Cache" on them (lol).

My Moondog is a pretty decent machine, not as fast as the FIC 486-PVT my main DX4 has, but it does great for what it is.

My chips were obvious fakes, "Writeback cache" written on them. They were soldered directly to the board. The traces all head off to the chipset though.
What suprises me more is that a lot of the BIOS images I can find online cause it to not even start. With them there is no activity on a POST card.
Andrew

Which version of the M912 is it ? There are two (1.4 and 1.7) and they are slightly different..look by the Keyboard connector it should have a V #.
Can you post a good picture of the board ?

Horun wrote on 2022-01-12, 04:41:

Which version of the M912 is it ? There are two (1.4 and 1.7) and they are slightly different..look by the Keyboard connector it should have a V #.
Can you post a good picture of the board ?

Apologies, I should have said. Its a V1.7 board. I'm at work currently, but will post some photos when home.
Andrew

Here are some pictures.
Andrew

I assume you did the jumpering like this:

According to the manual TAG RAM must be populated with a 256K (32Kx8) chip. Have you tried this?

In your picture there´s a 128K = (16Kx8) chip as TAG-RAM, which in the PC-Chips manual is documented in none of the supported configurations.

It´s a pity you´re restricted to 256K of cache in total with DIL 28 sockets in BANK1. You could go for 512K or even 1Mb with DIL 32.

majestyk wrote on 2022-01-12, 08:25:

I assume you did the jumpering like this: […]
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I assume you did the jumpering like this:

m912_cache.JPG

According to the manual TAG RAM must be populated with a 256K (32Kx8) chip. Have you tried this?

m912_tag.JPG

In your picture there´s a 128K = (16Kx8) chip as TAG-RAM, which in the PC-Chips manual is documented in none of the supported configurations.

It´s a pity you´re restricted to 256K of cache in total with DIL 28 sockets in BANK1. You could go for 512K or even 1Mb with DIL 32.

Hi
Yes, the jumpers are set as per the manual. Good call on the 128K tag chip though, I must have got mixed up, I'll swap that out.
I have also tried the 256k A configuration with 9x 32k x8 chips, again, jumpered as per the manual.
Every time it just behaves as if the cache just isn't there, no errors etc, just boots into DOS, with Cachechk reporting just the L1 cache.
Andrew

Do all chips have power supply between Vss and Vdd?
I would also check for damaged traces very carefully.

I had many cases of cache-problems, often BIOS reports "faulty cache" or a wrong cache size when single traces are interrupted or resistor arrays are broken, it´s a strange thing BIOS is reporting nothing at all here.

Hi
Sorry its taken a while, I've been very busy
All sockets have Vcc and Vss where expected.
No sign of broken traces. I'm fairly certain its a BIOS issue now...
Andrew