Heathen wrote on 2021-11-09, 13:12:

I have a Jetway 542B motherboard that I'm about to assemble alongside a K6-2 500 and 128MB of SDRAM. I'd initially read that bugs in that board's Aladdin V M1542 chipset mean that only 128MB of RAM can be cached without a performance penalty that may outweigh any increase in RAM (something to do with the TAG RAM implementation?) I've then seen conflicting advice across the years on this board about whether this was resolved in some board revisions, whether this is isolated only to those K6 chips without onboard L2 (i.e. pre 2/3+ CPUs) and how meaningful the impact really is.

This behavior is specific to almost all Super Socket 7 boards, with very few exceptions (a few boards with certain chipset revisions).
So, generally speaking, on a Super Socket 7, you want to use 128 MB for the max performance.

Heathen wrote on 2021-11-09, 13:12:

Is this problem genuine (i.e. if I were to add more SDRAM to this system, all else being equal, would the problem manifest) and how significant is the performance penalty?

Yes it is, but I would not call it a problem. 128 MB is arguably enough for a Super Socket 7, which in and of itself is a slow performing platform. Games that require more RAM will be heavily CPU limited anyway, so a different platform altogether would be recommended for those. On most boards, when going above 128 MB, the performance drop with a regular K6-2 is up to 25 - 30% (maybe more in certain instances).

Heathen wrote on 2021-11-09, 13:12:

Is it true that this issue would be resolved if the K6-2 were to be replaced by a 2/3+ with onboard L2 cache?

Again, I don't consider it an issue, but... yes, it would be partially resolved by going with a K6-3 or K6-2/3+ CPU. However, depending on the game/benchmark, you will still see a performance drop of up to 5 - 10% when going above 128 MB.

Heathen wrote on 2021-11-09, 13:12:

Are there other options to address the issue? I understand it's not a BIOS problem so not something a later or patched BIOS can address. Is this issue widespread for SS7 systems or isolated to Aladdin V chipsets?

If you want to play games that actually require more RAM, you want to avoid SS7 and go with a completely different platform.

Heathen wrote on 2021-11-09, 13:12:

I've seen some scattered references to certain SS7 boards suffering significant performance penalties swapping in 2/3+ CPUs, again possibly at a hardware level. Is this something I need to be aware of for this chipset/board? I'd obviously like to avoid swapping one problem for another!

This is something specific to Asus P5A rev 1.05 and 1.06. I'm not familiar with your board, but I would imagine that it's not affected by this issue.

Heathen wrote on 2021-11-09, 13:12:

[*]I've seen some scattered references to certain SS7 boards suffering significant performance penalties swapping in 2/3+ CPUs, again possibly at a hardware level. Is this something I need to be aware of for this chipset/board? I'd obviously like to avoid swapping one problem for another!

Look here:
Re: Just bought a “new” mobo

Re: Just bought a “new” mobo

Intels 430 FX and TX chpsets are limited to a cacheable area of 64MB. 430 HX has a limit of 512MB
In case of the ALI V northbridge it depends on the revision. Late revisions G and H (with fixed bugs) can cache up to 4GB, most early revisions are limited to 128 MB.
VIA´s MVP3 chipset with 512K L2 cache has a cacheable area of 128MB, with 1MB L2 cach it´s 256MB and with 2MB L2 cache the limit is 512MB.
So there´s no general limitation in SS7 mainboards, it´s all a matter of the chipset.

Abd there´s a workaround: If you are using a K6-2+ or K6-3+ CPU, these limitations don´t apply.

Pretty much as others have mentioned.
I find that with my K6-3+ there is very little to no penalty with using more than 128MB of ram. Likely less than 10% and closer to 5% in nearly all apps tested. Sometimes not any at all.
With that said...there is very little point to using more than 128MB ram with a S7/SS7 machine just like the others mentioned.
These machines shine in their DOS/Up to late 90s flexibility.

Thanks guys, much appreciated.

G