Dean Kukral wrote:
> Please be aware that PC's are undergoing a change right now, so that 
> compatability is an issue.
> 
> The latest motherboards are PCI Express ones.  This means that they take 
> PCIe video cards, not AGP cards.  Also, they require a PCI Express power 
> supply (24 pins), which - using an adapter - is backward compatable.  I 
> don't **think** that the older power supplies (20 pin) can be used with the 
> newer motherboards.

It's about 50-50 from experience.  Whether or not you can use a 24-20 
pin adapter (BA20019 from MWave) to connect an old PSU depends on the 
specifications.  A lot of the older ATX PSUs don't supply enough 
amperage on the +12V rail to drive a newer motherboard.  Modern PSUs 
provide two or three 12V rails, each with 10+ amps.

(You'll definitely need the full amperage if the system is loaded down 
with extra components like heavy-duty video cards or multiple hard 
drives.  Or a power-hungry CPU from the upper-end of the range.)

Now for the technical stuff...

I built an AMD Athlon64 3000+ 939 system using the ASUS A8N-VM CSM 
motherboard, 1GB of RAM, CD-ROM and 80GB HD.  In it, I attempted to 
re-use an older 300W ATX PSU.  The amperages for the various rails were 
+3.3V 28A +5V 30A +12V 15A +5Vsb 2A -5V 0.3A -12V 0.8A.  The +12V 15A 
rail was borderline for driving a more modern system, but since I was 
putting only a Athlon64 3000+ in with a single hard drive it was worth a 
shot.

The system ran fine all week as I put it through stress tests at my home 
office.  It even worked for the first day at the installation site.  But 
after being on the flaky power (local power company issues) for a few 
hours it stopped booting up.  Case fans would spin, but the CPU wouldn't 
spin up.  I went down to the local CompUSA and replaced it with a brand 
new Antec 430W TruePower and the machine has been running fine ever since.

More modern PSUs have +12V amperages in the range of 20-30A, split 
between 2 or 3 rails (10-15A per rail).  I suspect that the Antec 
TruePower 430W that I have in my parts pile with +12V 18A will probably 
not work, while the +12V 24A unit (also a TruePower 430W) will work with 
a 24-20 pin adapter.

(Ask me at the end of September whether those spare parts worked on 
newer motherboards...  I won't be building those systems out until early 
September.)

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                       Drew Dunn<[log in to unmask]>