UPDATE here:

I tried multiple other SB16's a 2940 with the OPL3 and another 2940 without it. Both exhibit the same random static the 1740 is producing. Next I hooked up a cheap pair of powered external Logitech speakers, and those too gave me the static.

So now I'm wondering if either:

A) the PC is too slow for the audio or...
B) I have the SB card is the very bottom slot of the 396 board. Above it are the SMC 8416 network card, Cirus Logic 5429 card, and finally the LG IO/IDE card.

Should the SB16 be above the video and Nic as IIRC and it's been a long time... ISA cards in the bottom could have issues when it's fighting over the NIC and Video? Maybe someone can chime in on that. I thought if I remember with ISA you'd want heavily
accessed devices on the top most slots...

This sounds like buffer underruns when only some games have the issue not all of them. 386 is on the slow end, 16bit playback takes more effort than 8bit of earlier SB cards. You could try choosing SB rather than SB16 and perhaps reduce sample rate when possible in game setup to see if it makes a difference.

Tiido wrote on 2022-08-15, 05:22:

This sounds like buffer underruns when only some games have the issue not all of them. 386 is on the slow end, 16bit playback takes more effort than 8bit of earlier SB cards. You could try choosing SB rather than SB16 and perhaps reduce sample rate when possible in game setup to see if it makes a difference.

I'll give that a try. I did notice that on top of the random bursts of static, when I move the serial mouse, there is constant static. Stop moving the mouse and I only hear the SB random static. Move the mouse and I hear both the SB static and the mouse static at the same time, almost as if the serial mouse has a separate issue introducing its own static.
I pulled the LGS Prime 2C controller and doubled checked the jumpers and settings. Then checked in the AMI bios to verify I didn't have any wrong settings. Finally I installed UNIVBE 5.3a for dos as after digging it seems SB had issues with Cirrus Logic cards and that could be a fix.
What's interesting about the static noise (not the static that the mouse introduces) is that when you hit Test Video in the text Murphy config, you get this hissing, static noise and the screen gets this faint TV snow effect.

I'll try changing the setting to SB instead of SB 16, but I have a suspicion there is a larger conflict going on between the Cirrus Logic card and the SB cards. The serial mouse could be related but it's odd you can hear the SB static and if you move the mouse you'll hear more static at the same time as the SB static I normally hear.
Tempted to just upgrade the system to a P75, although I really wanted to keep this 386 together for a while longer.

Mouse part does sound like CPU power running out, because when you move a mouse it causes interrupts to the CPU and it has to service them, taking away CPU time from what it was doing before.
But the video test thing is strange, apart from TV static which could be palette updates which are "snowy" on many video cards since RAMDAC palette update interferes with normal pixel output and you see it in screen fade ins/outs etc.

Tiido wrote on 2022-08-15, 12:01:

Mouse part does sound like CPU power running out, because when you move a mouse it causes interrupts to the CPU and it has to service them, taking away CPU time from what it was doing before.
But the video test thing is strange, apart from TV static which could be palette updates which are "snowy" on many video cards since RAMDAC palette update interferes with normal pixel output and you see it in screen fade ins/outs etc.

Appreciate the explanations, the video part is interesting something I didn't know so thanks for explaining. I think at this point I'll just update the system to a Pentium classic with a PCI S3 Trio64 or ATI.

I think a 486DX33 is probably the slowest thing that can run UAKM in any type of playable fashion

maxtherabbit wrote on 2022-08-15, 14:43:

I think a 486DX33 is probably the slowest thing that can run UAKM in any type of playable fashion

Yeah, IIRC it really wanted a Pentium, however the system requirements (I know... meaningless) calls for a 386/25, so I figured I'd give my 386DX-40 a go. I only have a single AT case, and so can only keep one build together which is why I wanted to keep the 386 together, as it's been hella fun the last 6 months using it. I also used the 386 to beat Tex Murphy 1&2 which was a "somewhat" fun experience since those 2 games are mad hard, and if you click the wrong dialog you can dead end yourself. This is my first time ever playing Under a Killing Moon, so maybe this is the universe telling me to experiencing it the way it was meant to be played, on a faster system 🤣. I never played any of the Tex Murphy games back in the day so figured I'd start this year, especially since I own (but never played) the new Tex Murphy Tesla Effect.

Currently the 386 has Dos 5.0 & Win 3.1 installed, so either I'll drop in a Pentium 75/100 on a older FX/HX/VX chipset so I can keep the same software setup, or I'll move to a faster Pentium MMX and go all out to 95/98. At least that'll let me install later software and games, also allowing for using a 100+GB Drive on a Asus TX97-E.

I tried a few configurations back when it was originally released. I started with an ISA-only 486DX-33, and it mostly worked, as long as you could tolerate the occasional stall in the video sequences. All of those disappeared when I switched to a VLB motherboard with ATI Mach32-based VLB video card and generic VLB I/O controller (the SCSI controller for the CD-ROM drive was still 8-bit ISA). In both of those configurations, I used a Sound Blaster 16 Basic and serial mouse, so those shouldn't be part of your problem.

Yes, performance was even better when I splurged on an early Pentium (mostly PCI, except for the SB16) some time later.

640K!enough wrote on 2022-08-16, 03:53:

I tried a few configurations back when it was originally released. I started with an ISA-only 486DX-33, and it mostly worked, as long as you could tolerate the occasional stall in the video sequences. All of those disappeared when I switched to a VLB motherboard with ATI Mach32-based VLB video card and generic VLB I/O controller (the SCSI controller for the CD-ROM drive was still 8-bit ISA). In both of those configurations, I used a Sound Blaster 16 Basic and serial mouse, so those shouldn't be part of your problem.

Yes, performance was even better when I splurged on an early Pentium (mostly PCI, except for the SB16) some time later.

Yeah, I reluctantly upgraded the system this week. Dropped in a P166mmx, 1x 32mb sdram, Asus TX97-E, S3 Trio64V2DX 4MB PCI, 40GB WD 7200, and a SB 2740 with the OPL3 Yamaha chip. I haven't tested Tex Murphy yet as I still need to install everything onto the blank 40gb and will probably be going with W95. I'll have some time this weekend to get that done and then I'll know if this will fix it, although I'm 99% sure it will 😀