Hi. I have an IBM 350 P100, and when I got it, it was working though there were some pecularities with the IDE channels. I had to put a new coin battery in for the CMOS. The machine is now in a state where I don't even get beeps anymore, even with the board out, on a non-conductive surface, with and without the unpopulated riser board, and no drives installed - only the memory it came with, and the CPU, a Pentium P54C-90. I've also taken out all the memory, and no beeps that way either.

When I try it in this state, the power supply and cooling fan that is plugged into the mobo spins up. if I have the drives plugged into power, but the IDE cables still not connected to the board, they spin up and do their basic power on things (it also has a 3 inch floppy and a CD-rom). Still no beeps though.

When I plug the HDD's IDE cable in, and the rest powered as previously, the fans and power supply don't spin up as much.. there's some life in the PS but that's it. This remains the same with multiple IDE cables. Still no beeps. I suppose they all could be bad, but I doubt it (as yet I don't have another PC to compare to/try it on).

It should be noted that ever since I got the PC, the secondary IDE connection has not worked. Also, on the primary, if I leave the secondary connection on the IDE cable blank, the machine won't boot off the HDD or even POST. I basically have to have a CD-ROM or an IDE-CF drive installed on the secondary (although now not even that gets the board to come to life). I've tried an IDE cable with no secondary plug, same behavior. I've tried other dual-device IDE cables, same behavior. I've tried the jumpers in numerous configurations - master, slave, cable select- with just the HDD cabled, and with both (also with multiple secondary device jumper configs), and the behavior doesn't change.

I've taken a multimeter to the power supply and checked the voltages with nothing plugged in, given that the commonalities are the power supply and the board and CPU. The PS reads that the power levels might be a bit high, on the order of .5V . I theorize - perhaps incorrectly - that with nothing at all connected to it, thus no load, perhaps the PS might be expected to run a bit high V-wise.

I got my hands on a different mobo, one for the slightly later Aptiva models that can still handle the same CPU and use the same PS and memory. I tried starting the new board on a non-conductive surface with just the CPU and PS connected (both of which were the ones from the 350), no memory, no IDE devices - and no life, no beeps and no video. However, that's with no riser board (because it didn't come with that and I don't have one that fits it, the one from the original mobo doesn't); I suppose it's possible that without the riser the board won't come to life. I confirmed the jumper for internal/external speakers was set for the on-board internal speaker.

So now we're down to PS, and CPU.

Getting an AT power supply with two additional P10 6-pin connectors (one for the riser and another, if I get its riser, for on board the Aptiva board) is not the easiest thing, and the couple I see listed cost more than the 350 and new mobo put together, so I am planning on pulling out the PS, opening it, and after carefully discharging those caps on it (I work on tube amps and radios too), giving it a once-over and see if anything looks hinky (and no doubt it needs a cleaning out). It's possible that plugged fully into the mobo, its behavior changes.

I have a POST tester card. when plugged into the PCI slots on the original 350 board's riser, I get no numerical POST codes, and the RST light stays lit. To me that says a short somewhere, maybe? I can't use the POST card without the riser on the new board. I get no life on the ISA slots of the original's riser at all.

I've found the new board's layout and pin-out info online, and the original board's diagram and settings are right on a sticker on the inside of the top cover of the 350, so that made things easier there. I also have just received another processor, though it's an MMX 233 that I was getting for a future project; perhaps I'll try that installed and see if anything changes. Though I am wary of the voltage needed on the MMX being different, I'm pretty sure the MMX can handle it long enough to see if I get beeps.

Can anyone think of anything I missed, or suggest anything else? The IDE issues seem to me to be hinting at SOMETHING, but what I can't grasp. Thanks!