As a long-time AWE64 owner and enthusiast, I wish I had an answer for you. From what I know, the people who upgraded the RAM on that card were few and far between, when it was sold in stores, and I suspect that most of the few people who ever did upgrade it, did so with after-market retro parts, years later.

For the Gold versions (CT4390, CT4540), the onboard and the upgrade are added together for a max total of 28MB. I would imagine that the Value versions work the same but I haven't actually tested that though I do have everything needed to do so.

Here is one current available upgrade path that is quite affordable:
https://www.serdashop.com/SIMMCONN

I actually converted the old PCB layout files to help get this project going. Had to go through multiple programs.

There is also a person on eBay selling boards that are more like the originals with the RAM soldered on. They are about triple the cost of the one linked above.

You can also upgrade a Value from 512KB to 2MB by replacing the onboard RAM chip and moving a couple resistors:
Creative AWE64 CT4500 upgraded to 2MB of RAM

cyclone3d wrote on 2021-08-02, 19:41:

For the Gold versions (CT4390, CT4540), the onboard and the upgrade are added together for a max total of 28MB. I would imagine […]
Show full quote

For the Gold versions (CT4390, CT4540), the onboard and the upgrade are added together for a max total of 28MB. I would imagine that the Value versions work the same but I haven't actually tested that though I do have everything needed to do so.

Here is one current available upgrade path that is quite affordable:
https://www.serdashop.com/SIMMCONN

I actually converted the old PCB layout files to help get this project going. Had to go through multiple programs.

There is also a person on eBay selling boards that are more like the originals with the RAM soldered on. They are about triple the cost of the one linked above.

I suspected that may be the case with the Gold series, as based on my research, Creative only appears to have sold 4MB, 8MB, 12MB and 24MB modules, and the box art for the AWE64 Value mentions it supports a maximum of 24MB RAM (due to KBs being less than MBs).

Booted up my system with an AWE64 Value and a SIMMCONN to check. I have a 8MB SIMM in the card, and it reports 8192KB of space available for soundfonts. On the 4MB Gold cards, I have to assume the 4MB module adds to the total storage, otherwise there would be no point in the 4MB upgrade module. That might be part of the point of the Value/Gold variation on the SIMMCONN. A SIMMCONN might be a good solution if an AWE64 Value develops bad memory, then, since it seems to entirely replace the onboard memory. Or maybe the first 512KB of the stick isn't used? Who knows.

In short,
Value does not sum together capacity, Gold does. (Though I don't know if the SIMMCONN might behave differently than the original Creative modules)
512KB+8MB = 8MB (I assume the 4MB module would result in 4MB)
4MB+4MB=8MB

Error 0x7CF wrote on 2021-08-02, 20:10:

Booted up my system with an AWE64 Value and a SIMMCONN to check. I have a 8MB SIMM in the card, and it reports 8192KB of space a […]
Show full quote

Booted up my system with an AWE64 Value and a SIMMCONN to check. I have a 8MB SIMM in the card, and it reports 8192KB of space available for soundfonts. On the 4MB Gold cards, I have to assume the 4MB module adds to the total storage, otherwise there would be no point in the 4MB upgrade module. That might be part of the point of the Value/Gold variation on the SIMMCONN. A SIMMCONN might be a good solution if an AWE64 Value develops bad memory, then, since it seems to entirely replace the onboard memory. Or maybe the first 512KB of the stick isn't used? Who knows.

In short,
Value does not sum together capacity, Gold does. (Though I don't know if the SIMMCONN might behave differently than the original Creative modules)
512KB+8MB = 8MB (I assume the 4MB module would result in 4MB)
4MB+4MB=8MB

this is all accurate

Error 0x7CF wrote on 2021-08-02, 20:10:

Booted up my system with an AWE64 Value and a SIMMCONN to check. I have a 8MB SIMM in the card, and it reports 8192KB of space a […]
Show full quote

Booted up my system with an AWE64 Value and a SIMMCONN to check. I have a 8MB SIMM in the card, and it reports 8192KB of space available for soundfonts. On the 4MB Gold cards, I have to assume the 4MB module adds to the total storage, otherwise there would be no point in the 4MB upgrade module. That might be part of the point of the Value/Gold variation on the SIMMCONN. A SIMMCONN might be a good solution if an AWE64 Value develops bad memory, then, since it seems to entirely replace the onboard memory. Or maybe the first 512KB of the stick isn't used? Who knows.

In short,
Value does not sum together capacity, Gold does. (Though I don't know if the SIMMCONN might behave differently than the original Creative modules)
512KB+8MB = 8MB (I assume the 4MB module would result in 4MB)
4MB+4MB=8MB

I have come up with memory expansion formulas below that could be useful for things like determining the real behavior of expanding memory on AWE cards (useful for improving emulation of these cards in various PC emulators).

Based on these observations and the information I was able to find online, the memory expansion formulas seem to work like this (although verification of these amounts IRL using actual cards may help confirm these figures):

Memory expansion formula on the AWE64 Gold (CT4390, CT4540):

4MB on card (and no memory expansion added) = 4MB

4MB on card + 4MB memory expansion = 8MB

4MB on card+ 8MB memory expansion = 12MB

4MB on card + 12MB memory expansion = 16MB

4MB on card+ 24MB memory expansion = 28MB

Memory expansion formula on the AWE64 Value (CT4380, CT4500, CT4520):

512KB on card (and no memory expansion added) = 512KB

512KB on card + 4MB memory expansion = 4MB

512KB on card + 8MB memory expansion = 8MB

512KB on card + 12MB memory expansion = 12MB

512KB on card + 24MB memory expansion = 24MB

Memory expansion formula on the Sound Blaster AWE32 if Creative memory combination guidelines are adhered to (CT2760, CT3900, CT3980, CT3990):

512KB on card enabled by memory expansion jumper (and no memory modules added) = 512KB

512KB on card disabled by memory expansion jumper and 1MB+1MB memory modules added = 2MB

512KB on card disabled by memory expansion jumper and 4MB+4MB memory modules added = 8MB

512KB on card disabled by memory expansion jumper and 16MB+16MB memory modules added = 32MB (28MB addressable due to EMU8000 4MB reservation)

Memory expansion formula on the Sound Blaster 32 if Creative memory combination guidelines are adhered to (CT3930, CT3600, CT3620, CT3670):

No memory modules added (card lacks built in 512KB RAM) = 0MB

1MB+1MB memory modules added= 2MB

4MB+4MB memory modules added = 8MB

16+16MB memory modules added = 32MB (28MB addressable due to EMU8000 4MB reservation)

Would it be possible to test memory combinations like 2MB+2MB or 8+8 on a real AWE32 or SB32? I don't think this has been verified or tested by anyone from what I can tell (It should work in theory, otherwise the AWE64 Gold with 4MB of base RAM would not have been able to be released with that amount of memory).

Most people don't have 2MB or 8MB 30-pin SIMMs to test with. They were never a standard product.

mkarcher wrote on 2021-08-02, 22:03:

Most people don't have 2MB or 8MB 30-pin SIMMs to test with. They were never a standard product.

I suspected this may be why the Creative memory module recommendations only suggested combos of 2, 8 and 32MB. There is another set of RAM on these cards, (I have also seen this in EMU8000 equipped E-mu Emulator and Proteus pro samplers/ROMplers as well, on a Proteus PCB picture I saw, the small RAM chip next to the EMU8000 was labelled "FX RAM") which is always next to the CT1971/EMU8000 or its combined CT8903/CT8920 derivatives. The chip is a Toshiba TC514256AJ-70 (seen on early revision of CT2760), ZMD UD61464DC (seen on CT3990, CT3980, CT3900 AWE32s, as well as CT3930, CT3600, CT3620 SB32s, CT3910 AWE32 Values, CT4500 AWE64 Values), TI TMS44C256DJ (seen on CT4380 AWE64 Value). There are other RAM chip brands I have seen next to the EMU8000 on various AWE card models (I have seen Mitsubishi and Siemens RAM chips being used), however it would take forever for me to collate and add them to the list above. The most common one I have seen is the ZMD chip seen on the AWE models that are considered go-to models on this forum (especially the real OPL cards).

I have found out that this RAM chip stores effect data (Reverb, Chorus, Bass, Treble, etc.) for the EMU8000 and it could potentially help with documenting how the effects processor on the EMU8000 works (useful for emulation as mentioned in a previous message). There are users on the forums who may have the resources to concretely determine this information (and some who may have better programming experience than me as well), as documentation on the EMU8000 is notoriously poor (apart from basic register info and the like). Things like the filter info are in expired patents as well.

This may be potentially unrelated, but it seems that there is documentation for CQM (expired patent US5900570A), and I saw a thread on this forum where someone was able to determine the frequency rate and KHz of CQM vs a real OPL3 as well. Research like this could pave the way for CQM (and other OPL clones, like ESFM, Crystal FM and others to be preserved and emulated).