P3, P4, AMD Power Supply Requirements?

  • Thread starter Thread starter Al Franz
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Al Franz

I have some older ATX cases which I was thinking of upgrading cheaply, which
have Power Supplies that worked with Pentium II's and III's. It is my
understanding that these power supplies will not work with P4 motherboard's
and processors, is that correct? What about any of the AMD processors?
Thanks.
 
Al said:
I have some older ATX cases which I was thinking of upgrading cheaply, which
have Power Supplies that worked with Pentium II's and III's. It is my
understanding that these power supplies will not work with P4 motherboard's
and processors, is that correct? What about any of the AMD processors?
Thanks.
Click to expand...
For P4 boards - and even some XP boards - you need the additional 12V
power connection which is not supplied by 'legacy' PSUs.

roy
 
Roy said:
For P4 boards - and even some XP boards - you need the additional 12V
power connection which is not supplied by 'legacy' PSUs.

roy
Click to expand...

but there's an adaptor you can get to turn a 4pin molex from the PSU
into the 4pin square for the P4, right?
 
but there's an adaptor you can get to turn a 4pin molex from the PSU
into the 4pin square for the P4, right?
Click to expand...

It wouldn't matter, as those older supplies wouldn't support the newer
processors, even if their total power output was equal. In other words,
don't try to use a 500W PII or PIII power supply (if such an animal exists)
with a PIV or any recent AMD chip. There's more differences between the
power supplies besides just connectors. -Dave
 
Dave said:
It wouldn't matter, as those older supplies wouldn't support the newer
processors, even if their total power output was equal. In other words,
don't try to use a 500W PII or PIII power supply (if such an animal exists)
with a PIV or any recent AMD chip. There's more differences between the
power supplies besides just connectors. -Dave
Click to expand...
Especially the 12 V output is essential for P4 and XP CPUs.

roy
 
Roy Coorne said:
For P4 boards - and even some XP boards - you need the additional 12V
power connection which is not supplied by 'legacy' PSUs.
Click to expand...

Not always, I installed an Asrock P4 motherboard recently, it didn't
even have the 12V connector on it. I'm running it with an old-style
ATX power supply with no problems.
 
Are the cases required identical though for the older Power Supplies and the
P4 and XP power supplies and associated motherboards. Can I just purchase
new power supplies and still use the old P2/P3 ATX cases?
 
Al Franz said:
Are the cases required identical though for the older Power Supplies and the
P4 and XP power supplies and associated motherboards. Can I just purchase
new power supplies and still use the old P2/P3 ATX cases?
Click to expand...

Yup. An ATX case will fit an ATX power supply. -Dave
 
-
Al Franz stood up at show-n-tell, in IHFKb.750842$HS4.5881949@attbi_s01, and
said:
Are the cases required identical though for the older Power Supplies
and the P4 and XP power supplies and associated motherboards. Can I
just purchase new power supplies and still use the old P2/P3 ATX
cases?
Click to expand...

Yes.

But, another question surfaces.....Do you really think all of that heat will
be gotten out by your current case? I, myself, used my old trusty midtower
when going to a P4 2.4C. Took me one week, exactly, to realize that I
needed a better case. Full tower, 7 fans. Your mileage may vary. What
climate are you in? What is your avg room temp? Other things to consider
when ramping up. I'm sure others, here, will also have experiences to
share.
 
DaveW said:
ATX power supplies have to be rated for P4's to run; they have an extra
power connector.
Click to expand...

Not exactly. P4 power supplies need to be rated for P4s to run. Of course,
if a power supply is P4, it's practically guaranteed that it will also be
ATX format. But the reverse isn't necessarily true. -Dave
 
Strontium said:
-
Al Franz stood up at show-n-tell, in IHFKb.750842$HS4.5881949@attbi_s01, and
said:




Yes.

But, another question surfaces.....Do you really think all of that heat will
be gotten out by your current case? I, myself, used my old trusty midtower
when going to a P4 2.4C. Took me one week, exactly, to realize that I
needed a better case. Full tower, 7 fans.
Click to expand...
Strontium
Click to expand...

I can't believe it ... straunch is a fanboy?
 
Al said:
I have some older ATX cases which I was thinking of upgrading cheaply, which
have Power Supplies that worked with Pentium II's and III's. It is my
understanding that these power supplies will not work with P4 motherboard's
and processors, is that correct? What about any of the AMD processors?
Thanks.
Click to expand...

www.formfactors.org
 
Al Franz said:
I have some older ATX cases which I was thinking of upgrading
cheaply, which have Power Supplies that worked with Pentium
II's and III's. It is my understanding that these power
supplies will not work with P4 motherboard's and processors,
is that correct? What about any of the AMD processors?
Click to expand...

The mechanical fit is exactly the same.

The type of processor doesn't matter, only the design of the
motherboard does. Some boards, mostly older ones, power the CPU from
the +5V source and use only a 20-pin power connector (a few also have
a 6-pin connector), but most newer boards run the processor from the
+12V and so have an extra 4-pin +12V cable to supplement the single
+12V yellow wire on the 20-pin connector. If your motherboard
possesses such a 2nd connector, be sure your power supply has a
matching connector or you could experience instability or even melt or
burn the yellow wire on the 20-pin connector. There are adapter
cables that let older power supplies work reliably with such
motherboards, by taking +12V from a disk drive power connector, but
since they use only one +12V wire instead of 2, even if they have 2
yellow wires themselves, they're inadequate for the fastest CPUs -- I
wouldn't trust one for anything faster than 2.4 GHz (Pentium 4) or
XP-2400+ (Athlon). But there still are some motherboards that don't
need the 4-pin connector, and they're often featured in the Fry's
Electronics newspaper ads.
 
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