I was adding some memory (DDR) to a Compaq 6000T computer to send to a
friend. This computer is a Celeron 2 GHZ that can accept up to 2 Gig of
RAM. The minimum speed is PC2100 and the MB has two slots for memory.
It had been running with 512 MB (2x256) and can accept either high
density or low density RAM in any combination up to 2 GB.

Now the interesting part: I purchased two sticks of low density PC3200
DDR so that I could put the maximum memory in the computer before
sending it out. Upon receiving the RAM I removed the existing RAM and
installed both sticks of PC3200 RAM WITHOUT having removed the A/C power
cord. Next I ran a memory test on the new memory to make sure no errors
occurred. It passed without error and recognized the full 2 GB.
Thinking everything was fine, I unplugged the computer from the A/C and
worked on something else.

Upon returning to the computer I plugged in the power cord to the A/C
and immediately the computer tried to start without having pushed the
power start button on the computer front. It did NOT successfully
start, but went into an oscillation of the power supply starting and
stopping every half second or so. (Pushing the power button during this
event had no effect at all.) During this oscillation the power on LED
would flash and the power supply fan would start and stop. I unplugged
the power cord after a few seconds of this and waited a couple of
seconds before plugging it in again. Upon plugging in the cord again,
the same thing happened again. It went into a cycle of turning on and
off the power.

Wondering what could possibly have gone wrong, I returned the old RAM
to the slots in place of the new RAM and plugged in the power cord. It
behaved normally, whereas the pushing the power button started the
computer. Thinking the larger size RAM might be drawing more current
and making the power supply suspect, I installed a 300W PS in place of
the 250W that had been in the computer. This had no effect, so I
returned the 250W one to the computer. The 250W power supply had an LED
on the back of the PS indicating (I suppose) that the standby power was up.

What I discovered was that if I waited to plug in the power cord again
until after the LED went out, the oscillation I described above would
NOT occur, even if both sticks were 1 GB PC3200 ones! It was as if the
standby voltage was not coming up fast enough when the PS had totally
discharged, but if you returned the A/C when the LED had just gone out
all was fine regardless of the RAM.

Since I did not want to give someone a computer that could go into a
power oscillation like I describe above, I wired in a reset button as
this computer did not come with one. After establishing that the reset
button did work properly, I wanted to see if pushing the reset button
could stop the oscillation if pushed. It did not! So it seemed if the
2 GB of PC3200 RAM was installed, and power was to be restored after
something like a power failure, the oscillation would occur. I could
not live with this possibility.

Since I wanted to install as much memory as possible in the computer, I
experimented to see if something less than the 2 GB of RAM would have
the same problem. It seems that as long as both sticks were not the 1
GB sticks, everything worked fine. I ended up installing one 1 GB stick
of PC3200 and one 512 MB (high density) stick of PC2700. From that
point on, it never failed as described above. So my question is this:
Why did the computer fail to behave properly ONLY when power was
completely removed and ONLY when two 1 GB sticks of PC3200 were
installed???? Since it is no longer a problem, I am curious to
understand what might have been happening. Any theories???