post a pic of the upgrade so we can see the pins you mention

So here it is along with my 5170 socket.

That upgrade module appears to be designed for a PLCC chip socket, as the vast majority of 286s were. The 5170 and 5162 used PGA sockets. Unless you make a homebrew adapter, it's not compatible

indeed! but what you can do it buy a 68pin PLCC socket, insert it in the blue motherboard socket and then install the upgrade on top

Ah nice! Here I was thinking I'd have to buy another 286 just so I could upgrade it to a slow 386. Ordered some sockets instead.

keropi wrote on 2020-05-14, 21:52:

indeed! but what you can do it buy a 68pin PLCC socket, insert it in the blue motherboard socket and then install the upgrade on top

That's not going to work. While it seems so, the pins are not connected the same way due to the way a PLCC socket has to route one row of pins to two rows in order. You would fry the whole thing.

I don't see why it wouldn't work. That's how I use 386 upgrades on my 286 board. The real issue is that the pins on the PLCC socket are flat not round, so it's not as secure as I'd like. Ideally you should remove the PGA socket and solder the PLCC socket directly to the motherboard.

You need an adapter for this. You can not replace a PGA socket with a PLCC socket by just replacing it. Their pin-out does not match. Google for "replace pga with plcc socket" if you don't believe it - there are even companies specialized in making such adapters.

http://www.cpu-world.com/forum/viewtopic.php?t=7129

http://www.vcfed.org/forum/showthread.php?274 … inout-questions

1. link: 13 years old, no pictures, just someone claiming something. Probably didn't even meant PGA, as I don't see how these were ever hard to find.

2. link: someone saying "shoud be the same". No outcome.

Anyway, this PLCC-to-PGA was a huge thing some years ago in the Amiga community. People wanted to use the cheaper PLCC 68882 FPUs on ACA turbo cards and installed PLCC sockets instead of PGA sockets - and frying the cards. This resulted in this adapter to correct the different pin-out:

I don't see why the 286 should be an exception here. For this to work, Intel would have had to rearrange the pinout for the PLCC version to coincidentally match the PGA pinout when using a PLCC socket, since it doen't just work "by design".

these are the 286 pinouts - I have no idea about 68882 or how motorolla wired it
I will get a PLCC68 socket in a couple of hours and will report back if this will work or not

edit: the pins round/flat are not such a big issue - I have modified a damaged 286->386sx upgrade and I used a PLCC68 socket : it fits perfect (and actually quite tight) in round pins and never caused any issues in the ~2 years I am using this

this is another mobo with round-pins + plcc68 socket - in both cases though the original 286 was plcc in a socket

Allright the results are in:
Putting a PLCC socket in the PGA socket will work just fine assuming you align the sockets correctly as seen by the PIN1 designation in the pinouts.
The lines I have drawn are the connections between I have measured and all checks out as it should be:

about 68882:
it is different because there are 4 extra internal pins , a plcc socket would never work for it anyways so that is one of the reasons why the special 68882 adaptor exists IMHO

Yeah, intel CPUs PGA and PLCC socket pinouts match.

Thanks keropi, you've spared me some minutes. So it's nothing to "rearrange", the pinouts are already 1:1, just the form factor differs.

quicknick wrote on 2020-05-15, 18:22:

Thanks keropi, you've spared me some minutes. So it's nothing to "rearrange", the pinouts are already 1:1, just the form factor differs.

exactly, just match "pin1" and you are good to go

That was a rollercoaster. 😀 I'll take care to line them up properly when the sockets arrive. I don't know what the jumper means on the upgrade board. I'm guessing it has something to do with the multiplier. Since my 286 is 6mhz, and this is a 386 16mhz upgrade, will it instead end up as a 386 - 12mhz?

yeah most likely the upgrade will get the 6mhz system clock and double it since I don't see an onboard crystal on it

Don't count on the clock doubling doing much of anything. Without cache, clock doubling doesn't seem very effective from what I've seen with TI486SXL CPUs. The more important features in this upgrade are improved memory management and 386 protected mode (if you have enough RAM).

Speaking of RAM, I have a AST Rampage board. It boosted conventional memory to 640k but I'm not sure how much expanded memory the board has because I haven't been able to boot to DOS. I think the Rampage board needs some kind of TSR to function.

The hard disk (type 2) won't boot and I have no disks. I tried the XT-IDE card but it still doesn't boot. I think this might be because it's using the earliest BIOS.

So in addition to this upgrade, I haven't been having much luck with anything else either. I've ordered some compatible BIOS roms to burn an alternative BIOS to hopefully sort at least the XT-IDE issue.