In comp.sys.ibm.pc.hardware.chips Robert Myers wrote in part:
I had previously noted the puniness of power supplies on OEM
boxes, but not by overloading them to the point where the machine
wouldn't run. I don't think that upping the RAM by 50% and adding
a HDD causing a power supply overload is a reasonable expectation.

Agreed. HDDs (especially 10k) can cause a heavy motor-start
load on the 12V but should otherwise be fine. One problem with
big OEMs is they are also aiming at EPA EnergyStar targets
which cause them to tight-size PSUs for max efficiency.
The German TuV may also have powerfactor targets.


Something else about this machine that is shaved very close is
the thermal design. It will not run for long with the side cover
removed. That wouldn't surprise me if the side cover included a
duct, but there are only holes strategically placed in the side
panel. The CPU has an enormous heat sink, but no fan of its own!

There is your clue, no CPU fan -- the cover is a duct. With the
cover off, air can bypass the CPU heatsink and slip straight to
[from] the PSU fan. I've built machines without CPU fans, and
you have to be very careful about airflow.


-- Robert R