Never heard of any issues there with the software (works fine on a Pentium 2) and haven't noticed anything odd with my SB Pro 2 cards. Could the ISA bus be running at a nonstandard speed I wonder? I'm not sure exactly how the cards derive their speed, but IIRC sbfmdrv uses the OPL chip for timing while PCM audio uses a different onboard timer. So the chances of them both being broken is odd, yet I would imagine they are both derived from the same underlying time source, which I thought was an onboard oscillator rather than the ISA bus. So possibly one of the oscillators on the card might have gone out of spec?

Probably the only way to know would be to get hold of a frequency counter or figure out some other way to measure the frequency of the crystal oscillators on the card to see if they need replacing. There's definitely no damage to the card? I think oscillator frequency is set by the size of the crystal inside the tin can, so possibly some minor damage may cause the frequency to drift.

I am running it on 550Mhz K6-3+ 550Mhz which is probably about same speed as P2. I can't see any damage on the card. If I run sbfmdrv without slowing down the pc, driver usually fails to load few times before it finally succeed and then if I play one of cmf file, I just get really loud noise, playing cmf files works fine if I disable both caches which should be about 386 speed normally. If I am only one having problems, perhaps I need to test it on some other computer to find out if the card is really broken.

Sounds like a good idea to test it on another PC as that would at least tell you whether the problem is the motherboard or the sound card. Almost certain to be the sound card though. As things age they just stop working so if the card is definitely broken don't throw it away as it is likely to be a simple repair, once the difficult job of discovering which component is faulty has been done of course!

I just tested few games commander keen 4, doom and quake. There was no problems with sound in those games and I didn't need to slow down the pc.

What revision is your CT1600?

If I remember correctly, there was some discussion a while ago about how maybe the earlier revisions had speed issues while the later ones did not.

cyclone3d wrote:

What revision is your CT1600?

If I remember correctly, there was some discussion a while ago about how maybe the earlier revisions had speed issues while the later ones did not.

I actually don't know. I have not seen any revision markings on the card.

The bottom left number "059234" is the revision information. In this case, it is Revision "05", which was designed in year 19"92", Week "34"

I did have issues with my CT1600, same revision, in a K6-3+ 450. I had to slow it down to about 200MHz for it to run properly in all cases.

fitzpatr wrote:

The bottom left number "059234" is the revision information. In this case, it is Revision "05", which was designed in year 19"92", Week "34"

I did have issues with my CT1600, same revision, in a K6-3+ 450. I had to slow it down to about 200MHz for it to run properly in all cases.

Thanks, it is good to know that there is probably nothing wrong with the card itself. Though probably it is not the right choice of sound card for my build then.

This is a later model CT1600.
The earlier ones have a copyright date of 1991, and they do not have their own crystal. They take the clock from the 14.318 MHz NTSC signal from the ISA bus.
This is an earlier one (like the one I have):

I use one in my 233mmx build and I have not found any problems with the CT1600 being speed-sensitive. The same games that need slowdown with the SB16 for example need it with the ct1600 as well. Never tried the bundled software though - except the initialization/mixer programs.

This isn't related to CT1600 but I wanted to ask. I also have even older CT1320C model of sound blaster which is I assume is probably even more speed sensitive. How fast PC it would start to have problems with? Would it be ok to pair CT1320C with a intel 486dx 33Mhz cpu?

I have tested a CT1350B on my 233mmx pc, it had speed issues (maybe opl2 related). The lowest I would go for this systems would be the CT1600.
I assume the 1320 would be worse....

My Sound Galaxy NX Pro seems to be speed sensitive with Pentium class and faster CPU's.
However, with a 486DX-33, it runs fine. I would guess that your CT1320 should run fine as well.

keropi wrote:

I have tested a CT1350B on my 233mmx pc, it had speed issues (maybe opl2 related). The lowest I would go for this systems would be the CT1600.
I assume the 1320 would be worse....

Yea, there would be a difference between OPL2 and OPL3. OPL2 takes longer between register writes.
The DSP should be exactly the same on both, using an Intel 8051 microcontroller.

The general consensus from what I have seen for sound cards with speed sensitivity is that it starts happening around 133Mhz.

cyclone3d wrote:

The general consensus from what I have seen for sound cards with speed sensitivity is that it starts happening around 133Mhz.

The CT1600 I have seems to be happy with 200Mhz, but not with 550Mhz. I am not sure if K6-3+ with 200Mhz would match speed with another cpu at 133Mhz though.

cyclone3d wrote:

The general consensus from what I have seen for sound cards with speed sensitivity is that it starts happening around 133Mhz.

That depends a lot on the exact sound card. For example, ESS AudioDrives are a lot less speed-sensitive than real SB cards.

It would be actually nice to have a list of speed sensitive sound cards and what is the max speed cpu that you can use them with.

Baoran wrote:

It would be actually nice to have a list of speed sensitive sound cards and what is the max speed cpu that you can use them with.

That would be impossible, because technically it's not the card that is 'speed-sensitive', but the application code. So the actual maximum CPU speed depends on the application.