If you can get that dallas battery fixed, then stick with the DEC. And as it is a Pentium system, and not an 486 system, then the S3 is the best option. Plus you do not have to waste a slot for Video/GFX. If it dies, then you have the Cirrus Logic card. Other than that, I think you are on the right track here. 80mb of Ram might be overkill though, and personally I am running my Pentium-166 (non-MMX) with 64mb. For the sound then I really do not know if a 2800 is good or bad. When you have it up and running, then why not fix the Compaq back to it's factory/default configuration?

I'd say : remove 16 MB, why ? L2 cache. Many pentium chipsets can't cache more than 64MB of ram, so that means if something use that (like the OS), your performance will drop.

Remember than in 1999, 64MB were still considered as a great amount of RAM. My pentium II system has 128MB of ram and has no issue to run even the most demanding games from the era. Since a pentium is much less powerful, the ram amount won't be a bottleneck at all.

People these days tend to put overkill amounts of ram because "more can't hurt", but in the reality, more ram could hurt the performance (not only that, but also programs with poorly made code like .... Windows 9x !)

Interesting. The box came with 80mb, so I was just going to leave it at that. It has 8 MB onboard the motherboard, two 32 MB simms and two 4 MB simms. I would have to get some new 72-pin simms to drop it to 64 MB.

You could just remove one 32 MB SIMM and go with 48 MB of RAM. That will be plenty for DOS/3.1. Lots of machines of that era had only 32 MB. Back in the 90's I ran Windows 95 on a Pentium 90 with 24 MB of RAM for years.

It is a socket 7 right?
Assuming that it is socket 7, if you don't have clearance issues i would suggest an all copper heatsink with fan.
For the cpu i would stick with a p166 as it is fast enough to some dos late dos games and with caches disabled it can run wing commander without it running too fast.
For video the s3 trio64v is nice, if you can, find a voodoo 2, i guess that for dos games you don't even have to sli.
For audio if you don't plan to use midi stuff the sb vibra 16 should work,for midi afaik it have some bugs, and i also don't know if the vibra 16 has one real opl-3 chip, at least the model that i have it doesn't seem to have aone ymf-262, the sound is nice though.
Abou the audio drive i really don't know.
The ram is fine to have at max 64mb, however it isn,t the end of the world if you have more.
Hard drive well it is all about you, personally i would go with one sd to ide adapter for convenience, or even a cf to ide adapter, transferring file that way is really nice.
If you already have a network card is a cool addon, its not required, but it is nice to have.

The maximum cacheable RAM can be calculated in the following way:
Write-thru: 2^n * C
Write-back: 2^(n-1) * C
Here n is the bit-width of the tag ram and C is the amount of cache onboard. For example, if your board has 256KB cache and your tag ram is 8bit wide, it can cache up to 32MB in write back mode or 64MB in write through mode.

Katmai500 wrote:

You could just remove one 32 MB SIMM and go with 48 MB of RAM. That will be plenty for DOS/3.1. Lots of machines of that era had only 32 MB. Back in the 90's I ran Windows 95 on a Pentium 90 with 24 MB of RAM for years.

The MB requires ram simms have to be populated in pairs, so that isn't an option for me.

Katmai500 wrote:

It is a socket 7 right?

It's a Socket 5. The current fanless heatsink is massive, so there is a lot of room for a heatsink with a fan. Yeah, if I upgrade a fan on the CPU might be a good plan with no real case fan.

.legaCy wrote:

For the cpu i would stick with a p166

I already picked up a P200 for only $3.... I know it is overkill, but I think it will be fun to mess around with the fastest CPU that was ever made for Socket 5. If it is a disaster I'll downgrade.

Katmai500 wrote:

i also don't know if the vibra 16 has one real opl-3 chip

The CT2800 has a real OPL3, unlike some other Vibra 16s cards.

.legaCy wrote:

if your board has 256KB cache

Yup, that is what is has!

Fimbulvetr wrote:

Katmai500 wrote:

You could just remove one 32 MB SIMM and go with 48 MB of RAM. That will be plenty for DOS/3.1. Lots of machines of that era had only 32 MB. Back in the 90's I ran Windows 95 on a Pentium 90 with 24 MB of RAM for years.

The MB requires ram simms have to be populated in pairs, so that isn't an option for me.

Ah yeah, that pesky 64-bit Pentium memory bus wouldn't like mis-matched 32-bit SIMMs very much. So 72 MB, 16 MB, or off to eBay to buy some SIMMs, I guess.

Yeah, the service manual says my board uses interleaved memory, so matched pairs of simms only.

Let's stop making assumptions about the chipset / memory controller. In So5 days things were far more diverse than later. i430NX could cache 256MB, OPTi and UMC had (awfully slow) chipsets that could handle single SIMMs...

Fimbulvetr, which chipset does the DEC system have? And what about the Compaq?

I think the DEC has a SiS 550x, can't remember on the Compaq. I'll have to take a look...

Then you're out of luck. The 5501 can't cache much: 32MB with write-back, 64MB write-through. See this (old, badly readable) document with a typo (5101=5501): https://groups.google.com/forum/?hl=de#!msg/d … Rk/u9YbGvBMh2oJ

As for the Compaq, I'm at a loss for documentation, but if it has a Compaq Triflex chipset it will probably cache anything you throw at it. Slowly. In that case you have an interesting choice: up to 32MB the 5501 will beat the pants off the Triflex, but if you need more than 32MB the Triflex will win hands down.

P200 will play a lot more late DOS games better, especially if you want to play in SVGA. If you only care about VGA, then the P75 will be enough. The P200 can be slowed down with cache manipulation too. Try SETMUL.

For DOS and Win3.x, you won't need more than 32MB, and 16MB may even be better. That keeps you under any cache limits and also avoids a handful of games that don't work right with too much RAM (Privateer has issues with >16MB, for example, and there are other games I can't think of at the moment).

The CL-GD5446 is a great card, very compatible and fast in DOS. I'd pick it over the onboard S3. S3 is also great, but in my experience, integrated graphics chips are a little slower than dedicated PCI versions. I'd avoid the Millennium--too many compatibility quirks.

Onboard (dedicated chip with its own memory) and integrated (chip or core sharing memory access with the CPU) are two very different beasts. Integrated VGA is almost always (more than) a little slower than dedicated PCI versions, which can be on their own cards or onboard on a motherboard. This S3 Trio64 is the same chip as you'd find on a PCI card, with its own RAM, and the same performance.

I was never a huge fan of S3 Trio chipsets, preferring the Vision 86x line for 2D and Virge for 3D, but in this case the advantages of a GD5446 or Millennium are negligible (for most purposes - for high-res, low colour work the Millennium is clearly superior) so I'd just go with the onboard chip.

Definitely a SiS 5501/5502/5503 chipset in the DEC. I found the data sheet for that chipset: (link fixed)

http://www.datasheetspdf.com/datasheet/SIS5503.html

I have no idea what chipset the Compaq has. The motherboard has Compaq-branded chips and I can’t find any documentation. I do know that the Compaq takes much longer to do the startup ram check with 32 mb of ram than the DEC takes to check 80 mb. The DEC just seems like a snappier machine so far, but I have yet to really put either of them to the test.

Compaq-branded? That almost certainly means a Triflex. Then it's the choice I stated: <=32MB the SiS5501 wins hands down, >32MB the Triflex wins.

Only other factor: OS

If you run DOS or Win9x, it resides in the top of memory, so uncached with too much RAM. If you run Linux it resides in the bottom, so cached regardless. As for NT/OS/2: no idea...

Here someone has made a convenient parts list of the Compaq motherboard (the Prolinea is the same as the deskpro, I checked the parts on my motherboard)

http://matthieu.benoit.free.fr/Compaq_Prolinea575.htm

I still can’t figure out what the chipset is.

Fimbulvetr wrote:

Here someone has made a convenient parts list of the Compaq motherboard (the Prolinea is the same as the deskpro, I checked the parts on my motherboard)

http://matthieu.benoit.free.fr/Compaq_Prolinea575.htm

I still can’t figure out what the chipset is.

Can you take a high-res picture of the motherboard? One we can read the text on the chips on?

Here is a pic of the Compaq motherboard.