1) I think that's slot 1 so you need a 5V processor, whatever you get.

BUT we could use the machine type number (like 2155, 2168, etc) from the sticker if it's there.

2) If you can find a "487", they're kind of rare, they're actually DX's that disable the SX you have installed, so that *is* an upgrade, though I'm not sure what limits you have on frequency (i.e. 20MHz, does it automatically switch to 25MHz if you put a DX2-50 or DX4-75 in there).

3) Aftermarket upgrades like the Evergreen 5x86, though faster than you were looking for, have been used successfully.

4) Here's a service manual for the PS/1: http://ps-2.kev009.com/pccbbs/aptiva/63g2028.pdf

5) Here's an article on PS/1 upgrades: http://ps-2.kev009.com/pcpartnerinfo/ctstips/4886.htm

Disclaimer: Never even touched a PS/1, just looked a few things up. You can do an internet search for specifics (like "PS/1 487", "PS/1 Evergreen upgrade", or even "PS/1 CPU upgrade".

Good call on the model number - it's a 2155-G44. As for searching on processor upgrades, most of what I find relates to machines with the processor soldered in, whereas this one actually has it in a socket. I'd rather use the bog standard 486dx2 (5v, of course) if possible, since they seem cheaper and easier to come by than anything that'd work in the 487 socket.
After spending some more time digging around on Google, I'm thinking I'm going to have to swap out the oscillator by the processor with a faster one in order to increase the clock speed.

bubish wrote:

Good call on the model number - it's a 2155-G44. As for searching on processor upgrades, most of what I find relates to machines with the processor soldered in, whereas this one actually has it in a socket. I'd rather use the bog standard 486dx2 (5v, of course) if possible, since they seem cheaper and easier to come by than anything that'd work in the 487 socket.
After spending some more time digging around on Google, I'm thinking I'm going to have to swap out the oscillator by the processor with a faster one in order to increase the clock speed.

If the money isn't a problem, you could always buy the parts and try it, and report back so we know how it worked!

If you already have a DX2-66, then yeah, at the very least you'd have to replace the clock crystal.

The only thing that makes me doubt that would be that all the 30-pin motherboards (I think yours would be a 30-pin memory board) were 20 and 25MHz procesors, the DX2-66 (33MHz bus) was a 72-pin motherboard.

Merovign wrote:

If the money isn't a problem, you could always buy the parts and try it, and report back so we know how it worked! […]
Show full quote

bubish wrote:

Good call on the model number - it's a 2155-G44. As for searching on processor upgrades, most of what I find relates to machines with the processor soldered in, whereas this one actually has it in a socket. I'd rather use the bog standard 486dx2 (5v, of course) if possible, since they seem cheaper and easier to come by than anything that'd work in the 487 socket.
After spending some more time digging around on Google, I'm thinking I'm going to have to swap out the oscillator by the processor with a faster one in order to increase the clock speed.

If the money isn't a problem, you could always buy the parts and try it, and report back so we know how it worked!

If you already have a DX2-66, then yeah, at the very least you'd have to replace the clock crystal.

The only thing that makes me doubt that would be that all the 30-pin motherboards (I think yours would be a 30-pin memory board) were 20 and 25MHz procesors, the DX2-66 (33MHz bus) was a 72-pin motherboard.

I have a PS/1 with 30 pin simm that have installed a 486DX33 (swap to a 486DX2 by me). so, 30 pin not means slower bus. IBM made a moltitude o combination of every computer they made, absolutely a nightmere.

Good to know that 30 pin SIMMs can work - thanks!
I think I'm gonna start with dropping in a dx2 and see if it will work underclocked. If it does, than I'll try swapping the oscillator. I wonder if that's something I can put in a socket for? Then I wouldn't have to keep de/resoldering the board if it doesn't work out.

http://www.andonelect.com/cat/Crystal-Oscilla … Sockets_84.aspx

Success!

At least partly. I picked up a dx2 66 of off eBay. I swapped the sx for the dx, set the jumper on the board to dx and... Nothing.
I tried the jumper back on sx and still nothing. Tried pulling the BIOS battery for a few minutes and still nothing.
I pulled the dx2 out, and was about to pop the sx back in when I figured I may as well give the dx2 a shot in the 487 socket and (with the jumper set back to dx), it booted up!
I haven't picked up a new clock crystal yet, so it's only running at 40MHz, but there was a noticeable improvement in both the benchmarks and the few minutes of Doom I tried.
The processor got rather hot, so I'll probably pick up a heatsink before long.
So next step for me will be to pick up a 66MHz crystal. Does anyone know what details other than pin layout and speed I need to look at when getting a new one? I tried searching the model number printed on the existing one (UC7-1A), but haven't had much luck. I'm attaching an image of the existing one, if that helps.

I picked up a 66MHz oscillator from my local electronics supplier (shout out to Gateway Electronics!), soldered it in place of the 40MHz one, and nothing 🙁
There are no beep codes or anything. I pulled the RAM out in the hope that maybe the bus speed is just to fast for the existing RAM, but still no beep codes or anything.
I'm not sure where to go from here, to be honest. I don't know whether the issue lies with my solder job, the oscillator itself (wrong specs of damaged while soldering), or if there's something else on the board that needs to be changed as well.
I suppose I could put the 40MHz back in just to make sure I didn't wreck the board itself.