You need to add the second TAG chip at the upper right corner for 512MB cacheable area. It has to be the same size as the one already present.
This only makes sense if there´s 512K L2 cache installed. Check the two chips for capacity first, otherwise you must replace them to upgrade from 256K to 512K.

majestyk wrote on 2023-07-13, 09:39:

You need to add the second TAG chip at the upper right corner for 512MB cacheable area. It has to be the same size as the one already present.
This only makes sense if there´s 512K L2 cache installed. Check the two chips for capacity first, otherwise you must replace them to upgrade from 256K to 512K.

It is a 512K Cache model indeed; there are 2x 64Kx32 Cache chips installed.

So I guess I need to add another N341256SJ-15 (or equivalent) at U1?

Yes, and add the torn off electrolytic C42 (if this is your board).

Does the BIOS already have the 64M/512M option? If not, you´ll have to unhide it with Modbin.

My 5DHX had a DIL TAG-chip so I added a DIL socket for the 2nd chip...

I can't seem to see where the torn off C42 is? Oh wow I just noticed this after you pointed it out! Can you confirm C42 as a 47uF 16V electrolytic? The board POSTs without that cap,but I'll replace it regardless.

I also noticed R72 also looks weird on your board?

I have the 1.80 BIOS on the board, if you already have a BIOS modded for 512MB cacheable RAM option, I'd be grateful if you could share it with me. Cheers!

This BIOS has the option enabled (it´s called "L2 Cache Cacheable Size"):

R72 is not populated, there´s only a trace that looks like a loose resistor.
C42 is 47µF 16V.

Thank you for all of this!

I wonder if I could also go with the DIP IC for the second TAG as well, or they have to be the same package..

You can as well mix. Both packages are pin compatible.

Thanks for the assist. I replaced C42 with a 42uF 25V electrolytic and all is well. I also checked and my board's BIOS does have the 64MB/512MB Caceable L2 Size option.

So I'm guessing installing this SRAM in a socket would work: https://www.aliexpress.com/item/1005005352245 … id=nuNs1ssLjwFP

Theoretically I can run an MMX 233 with 256MB RAM on this board then?

You should be able to go all the way to 512mb if you can get the tag and cache working correctly.

Well, actually, 512mb is supported without the tag and cache, is my understanding, but will be slow

There is one other way around this,

K6-3
K6-2+
K6-3+
Cpus can support fast large amounts of ram without need of on motherboard tag or l2 cache

In fact in some cases disabling motherboard L2 (L3) can increase performance with these cpus.

I’m gonna tag calamitylime in this thread, he has a nice guide you should read, though not for this board, very interesting.

This board can only do 2.9V or 3.3V so going beyond K-6 doesn't seem possible. Also 512MB would require 4x 128MB EDO 72-pin which I do not have 🙁

Those simms can be bought, the voltage issue can be overcome. 😀

If you wanted to…

Sphere478 wrote on 2023-07-14, 07:01:

Those simms can be bought, the voltage issue can be overcome. 😀

If you wanted to…

Well, assuming that I installed a VRM that does 2.2V, would the BIOS even recognize and run a K6-2/III? I guess that would also need patching?

appiah4 wrote on 2023-07-14, 07:09:

Sphere478 wrote on 2023-07-14, 07:01:

Those simms can be bought, the voltage issue can be overcome. 😀

If you wanted to…

Well, assuming that I installed a VRM that does 2.2V, would the BIOS even recognize and run a K6-2/III? I guess that would also need patching?

DIY Bios Modding guide Jan Steunebrink k6-2+/3+ 128gb

Socket 5/7/SS7 (Voltage Interposer) Tweaker. (Released)

That looks like a super interesting and super janky mod 🤣 I'll try it at some point I think, but the cache is the first bridge to cross for now!

This might be a very stupid question, but.. It looks like the SRAM IC that is soldered on the board is a SOJ28. I wonder if I can solder a SOP28 SRAM onto the pads for the second SRAM?.. That's the only cheap option I have locally it seems.

This IC in particular.

appiah4 wrote on 2023-07-14, 13:21:

This IC in particular.

55nS is far too slow!
Go for a 12nS or 15nS SRAM.