Ifirc the main difference is the way the processor works (and the speed of course), (this could well be a bit off so please correct me) 386 have no pipelines (no floating point) to speak of, also the 486 was the first chip to be able to synchronise the processor and the cache (anyone remember "cache on a stick"). Also different zif sockets (socket 3 to socket 5?), and the big one at the time, PCI architecture!!
Yay, it turned up today. Managed to fix the boot problem, had to set the hard drive paramters correctly in the bios. All works fine except.... Won't display mega drive games on my monitor Getting sound out, but after a read around, when it goes into mega drive mode, the vga output drops to 15hz, so I get a nice "out of range" signal on my monitor, oh well. Might make up a vga to scart lead. On the good side, I reckon this is compatable with the Mega CD. It has got exactly the same connector as on the side of a megadrive, underneath the catridge slot on the front of the pc. Exactly the same, same pin number, same spacing etc. Now to find an amstrad dev Mega PC CD add on....
I think it came with a multisync monitor originally. A multisync monitor can handle 15 hz. Though today multisyncs are obsolete since there are lots of TFT's that can show 15 hz.
