I'm not finding any pics of the voltage jumpers online. Could you post pics of the jumpers and what documentation you have? A lot of the time on the Socket 7 and Super Socket 7 boards, the undocumented settings were very easy to figure out.

Pull back to 64MB and retest your computer with some games to see if this helps. 128mb does not make sense on 233MMX as not much games can use best of these memory and one that does taxes the CPU too much. This computer is good for stuff to around 1998 games. Anything later, works well on PIII.

PCI S3 is great video card for this or CL-GD5446 2MB.

Cheers,

xxbeefydjxx wrote on 2021-12-21, 00:39:

[...]

My main question is, am I absolutely stuck with a 233mhz MMX or is there a possibility, that with some hardcore tinkering, heatsinks + extra fan in the front of the case I could run a K6-2 500mhz and take advantage of 3D-NOW + my 128mb RAM?
The machine does have it's own various jumpers and "VRM" so to speak which has some hidden options that are hardly documented, and I have various tools at my disposal (Multimeter, lots of 30AWG+ wire etc) if need be, all in the name of sending this machine right up to it's upper limits...

Hang on a minute... multiple issues with statements/assumptions here.

Are you 100% certain of the ID as PB640? If so I'd double-check the "Pentium MMX" and the "VRM". The PB640 had silkscreen for a VRM, but never heard of it being implemented, and indeed it almost never was on i430FX boards. The only jumper relating to voltage was J6A2, which sets VS vs VRE (3.2V vs 3.5V)
Here's the best documentation I'm aware of: http://uktsupport.co.uk/pb/mb/640.htm

If you are sure you have a VRM, I'd suspect you have a PB682/683 (i.e. Intel NV430VX) with i430VX chipset and split voltage design.

Both share the 64MB cache limitation (which every Intel So7 chipset has other than i430HX with extra tag).

The Pentium MMX is such an overengineered CPU, it's possible you're running it at 3.3V without ill effects, which is likely the case if you are sure it's PB640 and Pentium MMX. Will be pretty hot though and not something I'd recommend.

As for a K6-2 being able to circumvent that: nope. It's a CPU with L1 and no L2 cache onboard, just like the Pentium (MMX). You're probably mixing it up with the K6-3 and K6-2+/3+ which have L2 cache on-die. They can cache up to 4GB. But they run at significantly lower voltages, around 2.0V for the K6Plus, up to2.4V for the K6-3. That sounds close to 2.8V, but it's not close enough: those chips were nowhere near as over-engineered and running close to their thermal limits in-spec. You'd probably toast it at 0.4V higher.

If your board actually has a VRM you might be able to hack it to lower voltages (look up the VRM MOSFET, see if its datasheet says anything about other voltages, if not, see about replacing it with one that does - but get a BIG heatsink if you want to drop from 3.3V to 2.4V with a linear heatsink to feed a thirsty CPU like the K6-3), otherwise so not an option. Only way for an So7 CPU with on-die L2 cache is a voltage regulating interposer. Can't even guarantee that would work, as Intel has a penchant for BIOS that refuse to boot with unknown CPUs, although I don't know if that would apply here.

You could get 3DNow with a Winchip2 which runs at single voltage VRE, but its very poor clock-for-clock performance would negate any advantage 3DNow would give you (20% slower than an MMX without it), so no upgrade there.

If anyone knows of a proper MR.BIOS image for the PB640 board that would be hugely appreciated too, since the HDD limitations of the CP0R bios revision are not helpful when trying to use larger CF cards in an IDE converter...

There's an MR-BIOS for the NV430V X (PB68x Orlando), so not completely impossible, but problem is positive ID of the original (Intel) name. I've seen several people at Tomshardware refer to it as "Intel Advanced/MN-A", which would supposedly be a newer version of the Advanced/MN with PLB cache. Only problem is I can't find any Intel documentation for the board, and the BIOS versions I see listed for it don't match with the PB640. You *could* try flashing the Advanced/MN MR-BIOS on it (V097B50N), but given the flash ROM is soldered so recovery could be very difficult, I'd personally not risk it...

Other questions you may be able to help with:
VooDoo1 is good, but what would you suggest for the "best" PCI based 3d Accelerator card for the 95 era? I have a Nvidia FX5500 256mb but I think that would be best staying in my Dimension PIII build 🤣

In the Win95 era the "best" depends a lot on your software. That was long before OpenGL and Direct3D became dominant, indeed before 3Dfx did with Glide. If Glide games are your thing, the fastest PCI Voodoo would be recommended, although I doubt anything over a V2 would benefit a CPU this slow. On the other hand the PowerVR PCX was definitely a thing back then, with decent software support, if the specific games are up your alley.

Aztech has shockingly bad DOS support and whilst it is a reasonable digital sound card for the time, I would prefer something that does OPL properly, and support for WaveTable. Best or most recommended sound cards with Line-In Headers?

Oh? Which Aztech card do you have? I'd expect a workhorse like the MMSN837 (Sound16A in PB-speak) with this, and that in fact has excellent DOS support, with real OPL3, full SBPro2, bug-free MPU-401 MIDI and WSS thrown in for good measure. If it doesn't work in DOS, I'd suspect you should be doing something different.

I'm a big fan of Aztech 3rd gen cards like this to pair with buggy SB16 cards to compensate for their weaknesses (hanging notes and slowdowns in MIDI, stereo issues in SBPro2 games and in many cases CQM) and rarely have trouble. Just run CONFIG.EXE to set the resources manually to something sensible (A220 I5 D1 T5 U9 P330 usually does the trick) and reserve those resources in BIOS to avoid PnP conflicts.

Edit:
Hang on, been looking at that MR-BIOS repository and spotted V097B5NN for "PACKARD BELL 1.00.XX.CP0R". That BIOS string does match with what you posted earlier, so might definitely be worth a try.

dionb wrote on 2021-12-21, 02:03:

*SNIP*

Hi Dionb,

Thanks for your response.

I'm fairly certain it's the 640 (Again, mostly BIOS revision matching etc and I don't think there ever was a CP0R BIOS release for the newer 682/3s but I could be mistaken.), I will double check later in the week.

I believe you're right in that I am refering to J6A2 which indeed, only drops to 3.2v.
I have monitored the Pentium MMX to ensure it isn't getting overly hot and it doesn't seem to be doing too bad.

By Extra Tag, what do you mean? the Cache Modules?

K6-2 is out of the question for fixing the issue, I was looking at the later K6-3s and know that under absolutely no circumstances would a K6-3 be a "plug and play" solution on a socket 7.

That said, I got lucky on eBay just after putting up this post and have managed to snag a K6-3 400mhz with interposer, which will resolve the voltage concerns. Boxed, manuals and the Windows 95 patches included.

I am fairly certain that the board does have a VRM on it but I wouldn't like to say for certain, might be misremembering as I do watch a lot of 386/486/Socket7 videos online....

RE BIOSes, I will have a look at the V097B5NN link you posted, as I'm fairly certain that would indeed be the right MR-BIOS for these machines.
Thankfully, the machines have a header you can use that will boot to a recovery rom you can then use a Floppy Disk to boot from and recover the BIOS with a known working image. I always keep the original BIOS handy just in case. No saying that is bulletproof though if a MR-BIOS flash goes wrong. Willing to desolder and flash by hand if need be as I have the tools somewhere.

That will likely be the "make or break" between me being able to use the K6-3. Fingers crossed! Failing that, making sure this P MMX is comfortable will do just fine if it is the best I can offer up to this board.

RE Aztech cards, I just checked the photo I took of the sticker on the sound card and it is indeed the "Sound 16B SRS 3D".
Whilst it does work in DOS, getting the PB editions of these cards to work properly is a total pain in the behind. So far I have had issues with it not being detected which I resolved, it was the Config, but now I have issues in some dos games, the music is super, super quiet vs the sound effects which just straight up drown out anything else. (DOOM for example, music is super quiet but definitely there, but the sound effects for say, the door opening just blast on through). Would that be a potential EQ issue? Do these cards even have such a feature?

RE Video Cards/Accelerators:
Right now with the Voodoo 1 the machine runs like a dream especially paired with the P MMX 200. (Not a 233, my apologies.), maybe one day when the price is right I will put a VooDoo2 or possibly a 3 in this machine if I can get the K6-3 working. 😀

Thanks for your helpful pointers and insights. Goes a long way helping budding "retro" enthusiasts like me as this tech is older than I am 🤣. (not by much though, I grew up with a PB Multimedia Pentium 100 hand me down as a kid!)

Mission Success!
I received the K6-3 400 in the mail today post holiday delays, so decided to finally get around to installing MRBIOS V097B5NN on my machine after verifying that it was the right one for my machine.

MRBIOS installation worked a treat, Windows 95 OSR2 had no issues with that and all was detected and reinstalled.

I then installed the K6-3 400 and can confirm it is possible with the correct Interposer to install a K6-3 in a Packard Bell with a PB640 Motherboard.
(Pic of it running, that "Windy" fan technology is keeping this K6-3 incredibly cool, albeit at the cost of the fan being a bit on the noisy side (it's just the speed, not a bearing/wear issue))

For those interested, I snagged the I-O Data PK-K6HX400, originally marketed as a NEC/IBM PC Socket 7 upgrade in Japan, though if you can find any other S7 > SS7 Interposer with VRM, you're golden! 😀

Here is the Pentium MMX 200 I was running previously, despite there being an insane voltage difference.
I would not recommend this, the stock "VRM" solution still overvolts these poor CPUs quite hard, albeit the heatsink + fan combo I was using helped keep the heat down, Warm to the touch even after some real hot gaming sessions.

Next up for this PB will be replacing the Quantum Fireball 4GB HDD with an internal CF to IDE drive or maybe a 128GB SSD now I can finally make use of larger drives thanks to MRBIOS.

For those of you into numbers, here are some benchmarks under Windows 95 DOS Mode, using Phils Computer Lab Benchmark kit.

Pentium 200mhz MMX
128mb ram

VGA Benchmark 1.0: off the charts.
VGA benchmark 1.0c: 93.1

Chris' 3D Benchmark: 125.2 = 75.1fps
Chris' 3D Benchmark 640x480: 39.6 = 23.7fps

PC Player Benchmark: 34.3
PC Player Benchmark 640x480: 11.6

Doom Min Details: crashed.
Doom Max Details: crashed.

Quake TimeDemo: 33.6 FPS
360x480: 14.2 FPS

SysInfo 8.0:
CPU speed benchmark: 677.1 CI
Disk Speed: 28.8 DI
Scored 23.4 overall

Landmark system speed test:
1600.26MH CPU
3408.75MH FPU

Top bench: 285

Speedsys 4.78:
Memory bandwidth 77.55MB/s
PI: 149.99

L1 cache: 355.91MB/s 16kb
L2 Cache: 121.49MB/s 256kb
Throughput 73.54MB/s

K6-3 400mhz
128mb RAM

VGA Benchmark 1.0: off the charts. (66.6)
VGA benchmark 1.0c: 158.7

Chris' 3D Benchmark: 166.2 = 100.5FPS
Chris' 3D Benchmark 640x480: 45.0 = 27.5fps

PC Player Benchmark: 61.3
PC Player Benchmark 640x480: 18.6

Doom Min Details: 2134 gametics in 301 realtics
Doom Max Details: 2134 gametics in 1445 realtics

Quake TimeDemo: 41.4 FPS
360x480: 16.2 FPS

SysInfo 8.0:
CPU speed benchmark: 5141.1 CI
Disk Speed: 27.3 (test partially blocked by MRBIOS settings)
Scored 180.7 overall

Landmark system speed test
5058.30MHPU
6231.96MH FPU

Top bench: 301

Speedsys 4.78:
Memory bandwidth 89.16MB/s
PI: 454.42

L1 Cache: 1881.22MB/s (32kb)
L2 Cache: 877.59MB/s (256kb)
Throughput: 61.14mb/s

xxbeefydjxx wrote on 2021-12-23, 00:39:

dionb wrote on 2021-12-21, 02:03:

*SNIP*

Hi Dionb,

Thanks for your response.

Apologies for my late response this time. Was traveling during the holiday period, then recovering from a reminder of why travel during a pandemic might not be such a bright idea...

[...]

By Extra Tag, what do you mean? the Cache Modules?

No, tag RAM is basically an index keeping track of which parts of memory are being cached. In So7-era systems it's a separate little SRAM chip. Or chips in the case of the i430HX. Bigger RAM needs more tag RAM to keep track of caching., but the motherboard chipset determines how much is supported and how it can be used. Intel's are particularly inflexible. Larger cache size doesn't enable more cacheable area, nor does setting L2 to write-through instead of write-back (slower, but better than no caching). On i430FX, VX and TX you get one external 8b tag RAM and 64MB max cacheable area regardless. On i430HX, a second external 8b tag is supported, which increases it to 512MB cacheable - at least, if the motherboard has it implemented, or a socket/slot (COAST) for it.

Here's a pic showing the tag clearly:

This is a FIC PA-2005 with Via VP1 chipset, but priniciples are the same. The cache itself is the two rectangular TMtech chips above the CPU, the tag is the smaller EtronTech chip to the left of them. The other similarly-sized chip is a PLL (clock chip), so unrelated to cache. Your PB640 will also have a tag chip somewhere if it contains cache. If it's a cacheless PB640 (yes, PB stooped that low sometimes), then they'll have left off the tag too. I see on your photo there's no COAST slot in any event (that's the slot silkscreened on the extreme left next to the PC speaker).

K6-2 is out of the question for fixing the issue, I was looking at the later K6-3s and know that under absolutely no circumstances would a K6-3 be a "plug and play" solution on a socket 7.

That said, I got lucky on eBay just after putting up this post and have managed to snag a K6-3 400mhz with interposer, which will resolve the voltage concerns. Boxed, manuals and the Windows 95 patches included.

Wow, well done, those interposers are amazing. Be VERY careful with the pins though, they're much less sturdy than regular CPU pins. I also have one that I managed to use all of about three times before an essential pin in the corner broke off. Still trying to figure out how to fix...

I am fairly certain that the board does have a VRM on it but I wouldn't like to say for certain, might be misremembering as I do watch a lot of 386/486/Socket7 videos online....

No, it doesn't. The connector for a VRM is silkscreened to the left of the CPU on your first pic.

[...]

RE Aztech cards, I just checked the photo I took of the sticker on the sound card and it is indeed the "Sound 16B SRS 3D".
Whilst it does work in DOS, getting the PB editions of these cards to work properly is a total pain in the behind. So far I have had issues with it not being detected which I resolved, it was the Config, but now I have issues in some dos games, the music is super, super quiet vs the sound effects which just straight up drown out anything else. (DOOM for example, music is super quiet but definitely there, but the sound effects for say, the door opening just blast on through). Would that be a potential EQ issue? Do these cards even have such a feature?

They have a mixer, and yes, that is quite likely what needs tweaking, as the music is coming from the OPL3 (Yamaha YMF262) whereas the sound effects are digital audio - two different sources that can be set to different sound levels. I forget whether settings are persistent in EEPROM (I sort of suspect they are), but if you run MIXTSR.EXE you can change settings and after saving onload the TSR.

[...]

RE Video Cards/Accelerators:
Right now with the Voodoo 1 the machine runs like a dream especially paired with the P MMX 200. (Not a 233, my apologies.)

If you're massively overvolting anyway it might just as well be. Set multiplier to 1.5x (i.e. setting for Pentium 100) and it should run at 233MHz, as the P55c interprets the 1.5x setting as 3.5x 😉

[...]

Thanks for your helpful pointers and insights. Goes a long way helping budding "retro" enthusiasts like me as this tech is older than I am 🤣. (not by much though, I grew up with a PB Multimedia Pentium 100 hand me down as a kid!)

Sounds like a good reason to be nostalic about this specific one. I worked at PB's helpdesk a few years after these were current, but they still cropped up occasionally on the premium support lines. I was one of the few idiots there who actually enjoyed helping people with the then "ancient" (~5 year old) stuff 😜

xxbeefydjxx wrote on 2022-01-04, 18:28:

Mission Success!
I received the K6-3 400 in the mail today post holiday delays, so decided to finally get around to installing MRBIOS V097B5NN on my machine after verifying that it was the right one for my machine.

MRBIOS installation worked a treat, Windows 95 OSR2 had no issues with that and all was detected and reinstalled.

Nice, very nice work. That wasn't documented anywhere explicitly; now it is, which is good, as the PB640 is one of the commonest early So7 PB boards and MR-BIOS is always VERY nice 😀

I then installed the K6-3 400 and can confirm it is possible with the correct Interposer to install a K6-3 in a Packard Bell with a PB640 Motherboard.

Nice!

Shame you didn't try it the other way round though, I'd have been very curious about whether it would work with the default Intel OEM BIOS. Still, now we know which MR BIOS to flash there's no real reason to want that combination.

[...]

For those interested, I snagged the I-O Data PK-K6HX400, originally marketed as a NEC/IBM PC Socket 7 upgrade in Japan, though if you can find any other S7 > SS7 Interposer with VRM, you're golden! 😀

Very interested. I hadn't realized how big these interposers were in Japan - I can see quite a few options for some very nice prices, perhaps even nice enough to make up for shipping and import taxes..

For those of you into numbers, here are some benchmarks under Windows 95 DOS Mode, using Phils Computer Lab Benchmark kit.

[...]

Nice! Not quite stellar improvement in Quake, but that's to be expected with the relatively powerful P55C FPU vs the relatively weak K6-3 one. Quake 2 with 3DNow support would probably show a quite different picture.

P55C FPU is weaker, Quake just hyper-optimised to Intel. download/file.php?id=11663&mode=view

BitWrangler wrote on 2022-01-05, 00:38:

P55C FPU is weaker, Quake just hyper-optimised to Intel. download/file.php?id=11663&mode=view

Not exactly convinced by that graph. There are a lot of CPUs on there with exactly the same FPU (the two PPros, all the K6-2/2+/3+ etc) that still score very differently. Whatever it's testing, it's not pure FPU, that much is clear. Looks more like cache performance bench than anything else...

FPUmark'99 shows a different picture:
https://thandor.net/benchmarks/cpu/cpu?a=39&c … =0&i=0&s=Submit

Pentium MMX gets 3.57 points per MHz vs K6-3+ with 3.3 points per MHz on same platform (Aladdin V)

Still not enough difference to explain the disappointing Quake performance on the K6-3, so optimizations are also relevant, as is the inefficiency of a high multiplier - as soon as something's not in that big L2 cache, the K6-3 needs to wait just as long for stuff from the RAM as the P55C, which amounts to twice as many lost cycles.

dionb wrote on 2022-01-04, 23:01:

Nice, very nice work. That wasn't documented anywhere explicitly; now it is, which is good, as the PB640 is one of the commonest […]
Show full quote

xxbeefydjxx wrote on 2022-01-04, 18:28:

Mission Success!
I received the K6-3 400 in the mail today post holiday delays, so decided to finally get around to installing MRBIOS V097B5NN on my machine after verifying that it was the right one for my machine.

MRBIOS installation worked a treat, Windows 95 OSR2 had no issues with that and all was detected and reinstalled.

Nice, very nice work. That wasn't documented anywhere explicitly; now it is, which is good, as the PB640 is one of the commonest early So7 PB boards and MR-BIOS is always VERY nice 😀

I then installed the K6-3 400 and can confirm it is possible with the correct Interposer to install a K6-3 in a Packard Bell with a PB640 Motherboard.

Nice!

Shame you didn't try it the other way round though, I'd have been very curious about whether it would work with the default Intel OEM BIOS. Still, now we know which MR BIOS to flash there's no real reason to want that combination.

[...]

For those interested, I snagged the I-O Data PK-K6HX400, originally marketed as a NEC/IBM PC Socket 7 upgrade in Japan, though if you can find any other S7 > SS7 Interposer with VRM, you're golden! 😀

Very interested. I hadn't realized how big these interposers were in Japan - I can see quite a few options for some very nice prices, perhaps even nice enough to make up for shipping and import taxes..

For those of you into numbers, here are some benchmarks under Windows 95 DOS Mode, using Phils Computer Lab Benchmark kit.

[...]

Nice! Not quite stellar improvement in Quake, but that's to be expected with the relatively powerful P55C FPU vs the relatively weak K6-3 one. Quake 2 with 3DNow support would probably show a quite different picture.

Thanks,
I put the slight result skews down to the fact I was running MRBIOS completely stock and the W95 setup I am using is a little borked.

I'm sure if I set up an SD with dedicated DOS 6.22 image, and kept W95 Separate as it's own SD Card, I could get way better results, especially using an SD to ide over the well aged but still good for a preiod correct machine Quantom drive in there at the moment 🤣

I was curious also, about the Intel/Packard Bell OEM BIOS support for anything newer than the Pentium OverDrive w/MMX (that's the newest listed CPU, officially confirmed by PB support when users asked back in the day!), however I didn't want to risk it since a lot of the forum posts from back in the day, suggested that AMD cpus straight up don't post at all or had weird detection issues.
Besides, seeing MRBIOS with it's amazing feature set, and wayyyyyyy faster POST times on this board is insane. It posts and starts booting almost immediately especially with memory checks turned off etc, and you can get instant reboots.
Not to mention you're stuck with 32gb or lower drives in the OEM bios due to Allocation Table support being shaky at best.

I too didn't realise how big Interposers were in Japan until this came up. It was already in the UK as "Boxed, opened" and the seller didn't really know too much about it.
That said places like Yahoo Auctions JP are excellent places to look for older tech at insanely low prices, minus shipping and import fees though, they can be killer!

You're right that Quake runs better on the P55C FPU, but that is down to optimisation, not the P55C being faster. The K6-III FPU is lightyears ahead in terms of speed in that regard, shown when you run any CPU test that does FPU too (5x improvement in most cases!)
Anywho, I'm not just here for numbers. I am just glad that this PC is almost fully mega specced and will sit very nicely as a true portal into the 90s with it's early 3d Graphics, and great DOS gaming support. <3

dionb wrote on 2022-01-04, 22:38:

Apologies for my late response this time. Was traveling during the holiday period, then recovering from a reminder of why travel […]
Show full quote

xxbeefydjxx wrote on 2021-12-23, 00:39:

dionb wrote on 2021-12-21, 02:03:

*SNIP*

Hi Dionb,

Thanks for your response.

Apologies for my late response this time. Was traveling during the holiday period, then recovering from a reminder of why travel during a pandemic might not be such a bright idea...

[...]

By Extra Tag, what do you mean? the Cache Modules?

No, tag RAM is basically an index keeping track of which parts of memory are being cached. In So7-era systems it's a separate little SRAM chip. Or chips in the case of the i430HX. Bigger RAM needs more tag RAM to keep track of caching., but the motherboard chipset determines how much is supported and how it can be used. Intel's are particularly inflexible. Larger cache size doesn't enable more cacheable area, nor does setting L2 to write-through instead of write-back (slower, but better than no caching). On i430FX, VX and TX you get one external 8b tag RAM and 64MB max cacheable area regardless. On i430HX, a second external 8b tag is supported, which increases it to 512MB cacheable - at least, if the motherboard has it implemented, or a socket/slot (COAST) for it.

Here's a pic showing the tag clearly:

This is a FIC PA-2005 with Via VP1 chipset, but priniciples are the same. The cache itself is the two rectangular TMtech chips above the CPU, the tag is the smaller EtronTech chip to the left of them. The other similarly-sized chip is a PLL (clock chip), so unrelated to cache. Your PB640 will also have a tag chip somewhere if it contains cache. If it's a cacheless PB640 (yes, PB stooped that low sometimes), then they'll have left off the tag too. I see on your photo there's no COAST slot in any event (that's the slot silkscreened on the extreme left next to the PC speaker).

K6-2 is out of the question for fixing the issue, I was looking at the later K6-3s and know that under absolutely no circumstances would a K6-3 be a "plug and play" solution on a socket 7.

That said, I got lucky on eBay just after putting up this post and have managed to snag a K6-3 400mhz with interposer, which will resolve the voltage concerns. Boxed, manuals and the Windows 95 patches included.

Wow, well done, those interposers are amazing. Be VERY careful with the pins though, they're much less sturdy than regular CPU pins. I also have one that I managed to use all of about three times before an essential pin in the corner broke off. Still trying to figure out how to fix...

I am fairly certain that the board does have a VRM on it but I wouldn't like to say for certain, might be misremembering as I do watch a lot of 386/486/Socket7 videos online....

No, it doesn't. The connector for a VRM is silkscreened to the left of the CPU on your first pic.

[...]

RE Aztech cards, I just checked the photo I took of the sticker on the sound card and it is indeed the "Sound 16B SRS 3D".
Whilst it does work in DOS, getting the PB editions of these cards to work properly is a total pain in the behind. So far I have had issues with it not being detected which I resolved, it was the Config, but now I have issues in some dos games, the music is super, super quiet vs the sound effects which just straight up drown out anything else. (DOOM for example, music is super quiet but definitely there, but the sound effects for say, the door opening just blast on through). Would that be a potential EQ issue? Do these cards even have such a feature?

They have a mixer, and yes, that is quite likely what needs tweaking, as the music is coming from the OPL3 (Yamaha YMF262) whereas the sound effects are digital audio - two different sources that can be set to different sound levels. I forget whether settings are persistent in EEPROM (I sort of suspect they are), but if you run MIXTSR.EXE you can change settings and after saving onload the TSR.

[...]

RE Video Cards/Accelerators:
Right now with the Voodoo 1 the machine runs like a dream especially paired with the P MMX 200. (Not a 233, my apologies.)

If you're massively overvolting anyway it might just as well be. Set multiplier to 1.5x (i.e. setting for Pentium 100) and it should run at 233MHz, as the P55c interprets the 1.5x setting as 3.5x 😉

[...]

Thanks for your helpful pointers and insights. Goes a long way helping budding "retro" enthusiasts like me as this tech is older than I am 🤣. (not by much though, I grew up with a PB Multimedia Pentium 100 hand me down as a kid!)

Sounds like a good reason to be nostalic about this specific one. I worked at PB's helpdesk a few years after these were current, but they still cropped up occasionally on the premium support lines. I was one of the few idiots there who actually enjoyed helping people with the then "ancient" (~5 year old) stuff 😜

Apologies, I didn't see this message above too!

Thanks for the heads up about TAG Cache and the mixer hints, I will take another look at the motherboard once the longer IDE cable arrives (hopefully this weekend) and see what the trick is with this board.
Maybe take a few more photos whilst I'm in there 😎

I have a suspicion there is more we could do hardware mod wise, but alas it may not go much further than the current setup.

That's pretty cool you used to work on the PB help desk, I'm sure you probably remember quite a few quirks then 😁