That's a pretty awesome system. I assume it's got a 486SLC installed, because I don't think there were any proper 286-to-486 upgrades. It's in desperate need of a PGA graphics controller and an IBM music feature card, though.
Yeah, the chip is a surface mount soldered directly onto some kind of breakout board with a couple of other chips so it could fit into the PLCC socket the 286 used. The 486 has a built in math coprocessor, so I'm not actually sure what IC is populating the spot for it right now other than it's got a big AMD logo on it (my photos of the inside are pretty low resolution). The original chip is interesting because it would have been an AMD branded Intel N80L286-8. I have an an extra non-functional Compaq Portable II for spare parts that still has the 286 and 287 math coprocessor on it.
Again, since all I have is this crappy picture to go I can't read everything on the chip but it looks like it does in fact have a TX486SLC/E processor in it, clocked at 18MHz. The diagnostic floppy detects it as a 386 but Norton's sysinfo program properly labels it a 486 for some reason. I'm in the processing of diagnosing a system clock issue (I put a new battery in a while ago so that's not it), so when I open it up I'll photograph everything again with a nice camera in good light and write down all the ICs so I can buy replacements in the future.
I love the greenscreen, after all these years it's still super bright and has no burn in. A better card sure would be nice since I can't afford a CGA monitor right now. However, I suspect that I won't be able to use the 9" built in monitor with a different video card, not without modifying it anyway to have an extra header and some fancy circuitry anyway. I definitely want to put a soundcard in. The PC speaker plays music fine but it's monophonic. You can sort of simulate polyphonic music by switching tones really fast but it doesn't sound especially good. What I'd like to do is see if I can get a combination soundcard and serial expansion card. I'd like to put an internal 8 ohm speaker mounted on the card, then use the extra serial port to connect to an raspberry pi mounted internally powered off the 5V rail, then connect to it through a terminal program and run elinks so I can browse the Internet using modern wifi networks. I've got one serial port already but I use it with a mouse occasionally.
