On Wed, 2007-06-06 at 12:27 +0100, Paul wrote:
In my collection of "odds'n'sods", I have a PSU with a 20 pin connector with a mechanical on/off switch (about 200W as I recall).. Also have a couple of MoBos that will accept either P8/9 or 20 pin connectors so Chris' combination is quite possible..
It was more the combination of 2000 era CPU in a 1995 era form factor that bothered me The secondary monitor feed is inconsequential as they were still commonplace well into the ATX form factor..in fact some aftermarket ATX PSU's some come equipped with this.
On the subject of power supply types there is an additional (short lived) configuration that I had long since forgotten about that caught me out when fixing a box the other day. That is 20Pin ATX header plus one half of the P8/P9 pair for the CPU power (this predates the 4 pin 12V CPU power connector you see now)
If you want real oddball, also have a PSU with just floppy/HD connectors plus a single 2x2 block (just +5V & +12V rails).
Actually I don't think we are that far from this sort of configuration becoming commonplace. Some of the ATX suppy rails are already technically redundant since the demise of the ISA bus, Modern machines already tend to source CPU core from the 12V rail and use switching regulators to bring it down to the correct voltage on board so the +3.3 is becoming less and less relevant.
Already the -5V is technically optional even to the point that it is not actually included in the latest revision to the ATX spec, the -12 could soon well follow. The only problem being that the seemingly duplicated rails coming out of the ATX header are actually provided by separate secondary circuits in the PSU to avoid power fluctuations on the drive and accessory rails causing problems on the supplies to the chipset. But if you are going to derive the critical stuff from on board DC-DC conversion this problem mostly goes away.
Actually the subtle revision changes in ATX spec between 1995 and now mean that Modern PSU's are not necessarily fully backward compatible. As well as the above mentioned now optional supplies the ratio of capacities have changed. Specifically the capacity of the +5 rail has dropped relative to the PSU's maximum output rating.
Crumbs I will stop writing now, I am starting to sound like a geek :-)