Anonymous Coward wrote:What I'd really like to see is a snap on 386SX module with a test socket that lets you drop in NOS PQFP100 386SX type chips with an optional VRM. For example, I have unsoldered TI486SXLC2-66 chips that I would like to use to upgrade my 386SX boards, but I can't simply do a cut and swap because they're 3.3V parts.
I'd been thinking about this for the 3.6v IBM SLC2 chips. The 386sx package is annoying, because it has the wings (BQFP, b as in bumpered), and the pin pitch is difficult - 0.635mm - to work out to .25mils when doing PCB layout - this was JEDEC standardized but the pin pitch for QFPs didn't go much further than the 386EX.
There is a very hard to get part (I had to have a courier in Japan find it) that I have on the way, a Yamaichi IC 149-100-028-B5. It's cool because the footprint matches the device you are replacing. It looks like this:
Sometimes on 386sx motherboards, you'll see what was meant for 3 rows of pins on the outside of the processor. That is for a somewhat larger socket:
3M 2100-7243-00-1807 - if you search on ebay you can find it.
I'm still looking for the snap on part - it's a difficult find. I'm hoping TopLine (who has previously manufactured the socket) still has it, as they still manufacture the dummy 386 chips (for practice soldering).
The way these things seem to work is that the hold the FLOAT# pin on the real CPU, and then take over.
Anyway, happy to hear more input.