You can upgrade it for 2MB cache with 2 chips 128K x 64. You will also have to replace the TAG chip with a 64K x 8 one.

If you´re going for 1MB (just add a second 64K x 64 chip), you don´t need to upgrade TAG-RAM, just leave it at 32K x 8.

In either case there will be some adjustment necessary by changing 0 Ohm resistors.

majestyk wrote on 2024-04-04, 09:25:

You can upgrade it for 2MB cache with 2 chips 128K x 64. You will also have to replace the TAG chip with a 64K x 8 one.

If you´re going for 1MB (just add a second 64K x 64 chip), you don´t need to upgrade TAG-RAM, just leave it at 32K x 8.

In either case there will be some adjustment necessary by changing 0 Ohm resistors.

If we do, we will add 512kb only.
Can you please explain what to change at resistor level and where?

Mamba wrote on 2024-04-04, 10:20:

Can you please explain what to change at resistor level and where?

There are usually 1 or two resistors for grounding / connecting the unused / used address lines at the TAG chip (high numbers) and another resistor (combination) to tell the BIOS what´s populated. This mainboard can be configured for 512K, 1MB and 2MB so it must provide the resistors for all 3 cases.
Either compare with a 1MB version of the mainboard or do some measuring / try and error.

majestyk wrote on 2024-04-04, 13:04:

Mamba wrote on 2024-04-04, 10:20:

Can you please explain what to change at resistor level and where?

There are usually 1 or two resistors for grounding / connecting the unused / used address lines at the TAG chip (high numbers) and another resistor (combination) to tell the BIOS what´s populated. This mainboard can be configured for 512K, 1MB and 2MB so it must provide the resistors for all 3 cases.
Either compare with a 1MB version of the mainboard or do some measuring / try and error.

Yes, that was the plan, to compare with a 1Mb board.
But I fail to find one clear picture online.