A Tualatin 1.4GHz should be on par with your current CPU in terms of power consumption (because of the newer 130nm node), so nothing to worry about here except CPU compatibility with the motherboard.

IMHO, unless you get low framerates (sub 20FPS), the FX5600XT is good enough. If you still want to upgrade, go for the 5900XT, because it's really good for DX8 games.

The 6800 is more suited for a Windows XP build.

I'd say around a Geforce 4 is suitable for that system. I had a 6800 on my Athlon XP 3200+ in 2004, so it's significantly newer. That means newer drivers and/or worse compatibility with old games.
The PSU is low for cards like that!

Danoxman wrote on 2020-07-03, 10:28:

Hello, […]
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Hello,

I have an Deskpro EN with a PIII 866, and I came across two gpus for a cheap price. The FX5900XT and 6800.
I know that the 6800 is way better, but I want to add a Tualatin 1.4 in the system, so I wonder what card to choose or if the 6800 is waaay overkill.
Its actually the same price for the GPUs.

My plan is to play games up to around Quake4 decently(If possible), but want to build mostly for fun and some older gaming.

I have the original PSU in the system, 200W, will that even be suffiecient for any of those and when i add the Tualatin?

My current hardware:

Deskpro EN
P3 866 (Coppermine)
2x 256mb 133 Ram
FX 5600XT
140Gb HDD
DVD and Floppy
SoundBlaster Live!
Win98SE

If you can get a 5900 and a 6800 for a cheap price, I'd get both of them and worry about what to use them for later.

Your PSU will probably be insufficient with either card btw. The difference in power dissipation (and thus in how much energy they will use) between a Coppermine 866 and a Tualatin 1400 should be negligible.

There are Windows 99SE drivers for the 6800 and as it's a way better card I would opt for it.

Should you ever wish to setup the system as Dual boot with XP then the latest XP Driver is way more recent.

I was never able to fix a stability issue with Geforce 6 6600GT and a Geforce 6 6600 on my 815 board under Windows 98 SE . Issue was a freeze or suddenly switch to incredibly slow screen updates when scrolling . Exact behaviour varied with driver version (tried a lot of those).

I ended up with using a Geforce FX 5900, which works fine .

Then it might be a FX5900xt then, or a TI 4xxx (but those are not cheap that I found).

If I want to replace the PSU, must I find a Compaq one, or can i buy whatever?

For the PSU, I do not know and would not hazard a guess . If you can't get official documentation, what I would suggest is checking if there is a pinout on the PSU label and, if there isn't, using a multi-meter to map out voltage and ground pins on the PSU connector . Then you can compare with official standard docs and be certain .

EDIT: For the video card, I often see them at prices I would consider reasonable (less than 75 US with shipping to Canada for an FX 5900 variant) from eastern European vendors on a certain auction site . I actually have two on order for my spare parts bin.

Is 250w enough for my plan, or should i go for 300-350?

I have found some 250w Compaq psu's on ebay, but have no clue what to look for when it comes to compatibility.

Anyone here that knows some, or have upgraded the psu on a Deskpro EN?

What's the reference on your current supply?-

Part No.
Spare No.
Series PDP No.

Some of these old Compaq PSUs are custom sizes and may not fit your case

Part: 221256-001
Spare: 224061-001
Series: Pdp-110p

That's the downside of those Compaq cases... I have a DeskPro EP/SB and most standard PSU's won't fit 🙁

Danoxman wrote on 2020-07-03, 17:58:

Part: 221256-001
Spare: 224061-001
Series: Pdp-110p

OK, so I assume you've got a Deskpro EN Convertible Mini Tower, rather than one of the SFF / compact desktop versions. The PSU enclosure is definitely Compaq custom rather than standard ATX and there doesn't seem to be a uprated genuine Compaq replacement for this 200W unit. Whilst you may be able to shoehorn a better generic PSU into the space (either a small footprint ATX or an SFX PSU) another problem is that the 24-pin connector on the current supply is not wired to standard ATX spec, but to Compaqs own so you'd have to work round that as well.

I've been looking around, but came to the decision to keep what I have, and maybe upgrade the cpu to a tualatin at best.

I think I might do an P4 or AthlonXP build next, from the ground up.

But thanks for the help guys! Now I know where I should go when I have questions.