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DIY 286 to 386 upgrade?

M

mbates14

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Now I know this might be a bit "out there", But I do know there were companies involved in making 286 to 386/486 upgrades. But those are almost unobtanium and go for substantial prices when they do come about.

So... Does anyone happen to have schematics, or know of whats involved in processor retrofits? Just curious.
 
I had one which was a PC-on a card that plugged into an ISA slot. It was no stellar performer by any means. I may actually still have one somewhere.
 
The Austek chip is a cache controller. The cache is what really makes the upgrade go faster than the original 286.
 
Unfortunately that doesn't really help my situation.

The card is loaded with PAl chips which.... well there a mystery.

I was hoping someone had a magazine article or a application note or something from years past that explains how to adopt a 386 into a 286 bus.

Everything between the two is the same except for the state control lines on the output. These control lines are used to signal bus conditions such as a protected memory read IO read etc....
 
nestor said:
The Austek chip is a cache controller. The cache is what really makes the upgrade go faster than the original 286.
Click to expand...

To be fair, 32-bit wide access and zero wait is what makes it go faster and why most upgrade options had local RAM. You can achieve that with modern 10-15ns SRAMs without cache control.
 
Zenith used to have a 486 upgrade board for the Z-248 series 286 machines. The 248 was very similar to how an S-100 board was set up, and the upgrade replaced all the discrete cards with all in one full length card with the CPU, I/O, FDD & HDD controllers, memory, and video (if I recall correctly) onboard.
 
g4ugm said:
Why? If you want to experience 386 or 486 computing buy a 386 or 486. they are still plentiful and cheap...
Click to expand...

+1

I don't quite get trying to upgrade a vintage system to a completely different level. Why even collect the vintage system the first place if that is what you want to do?

I bought an XT/286 because I wanted an 80286 machine.
I bought a Deskpro 486/33M because I wanted an 80486 EISA machine (although it does have a 66Mhz CPU card in it now but that was an original option).
It would make zero sense to me to try to upgrade the XT/286 to a 386 or 486 level instead of just using the 486/33M.
 
We have had a couple of threads like this where folks want to upgrade 386sx to 486 or 286 to 486 with after market upgrades.

From what I remember those were all expensive in the day, for what you got. Often they didn't work that well as the CPU often is not the only bottle neck, and you still ended up with a slow disk and slow RAM or a 32-bit CPU bodged onto a 16 bit bus. They must be like hens teeth these days and I wouldn't want to spoil a nice original 286...
 
I have an Evergreen Technologies "Rev to 486" module which incorporates an "IBM/Intel 486SLC2-66" along with the "Math-Co sx" FPU. It also has a utility disk which kicks everything in gear. I used to run the thing in a Packard Bell 286 with a memory expansion module. The PB also had an upgraded 3rd party BIOS chip which got you into a larger HD. With all of that, it was a dog compared to my 1st 386. Unless you just want to display the thing or use it as a conversation piece, I would strongly recommend directing your resources toward a 386 or 486. BTW, this module occupies the space that the 286 was located in and does not clip on, it plugs in. I'm not in the market (yet) to sell my adapter, but am willing to post a few pictures if you interest is still piqued.
 
I'm interested in those pictures :)

I am one of the users looking for one of these upgrades. In my case, I want it to upgrade a specific machine: my IBM PS/1. What I look for is taking it to its limits, because it is a very specific PC with its DOS in ROM, proprietary floppy and hard disks, tied to its VGA monitor with the internal PSU, etc. I already have some 386 and 486 machines and I know that these 286-to-386/486 upgrades can not provide the same performance. The processors used in these upgrades are in 99% 16 bit external bus parts like the 486SLC(2), but they give a boost thanks to the internal cache and sometimes the internal frequency multiplier.
 
I have tried several of the 286 to 486 upgrades. They provide quite a boost if you can actually get all the features enabled. The Rev to 486 with the SLC2-66 for example does not enable the integrated 16kb L1 cache by default. Some modules also start with the CPU multiplier set to 1X by default. The other modules I tried were based on the Cyrix/TI chips. These were also not bad when running at full speed, but on a system with a slow system clock, it's generally best to have as much cache as possible (Cyrix chips have 1kb, TI sometimes have 8kb).

I have seen pictures of some 286 to 386SX upgrades that didn't seem to use any additional circuitry. I think it was just a 386sx grafted onto a 286 PGA adapter. I think I've even seen a prototype of the i386SX that used a 286 pinout. It should be possible to design a DIY adapter. It would help if we could actually track down the upgrade I'm thinking about. Obviously it would be be no faster than the original 286 that was originally in there, but it would at least let you run 32-bit code. If you wanted to go one step further I suppose you could use a ti486SXLC (internal cache and clock doubling available), but I don't know how compatible those chips would be on older boards without hidden refresh.
 
I found a low resolution shot of the adapter in mind:

2005929141111569.jpg


The website appears to be broken. Maybe if you contact the owner you can get high res shots of the top and bottom.
 
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Here's the photos of the Evergreen 286 to 486 kit along with the cache enabling software disk.
 
KC9UDX said:
Nor can I.
Click to expand...

You know, I was looking on my big rig this morning and couldn't see the pictures either. I'm on my laptop now and they show up okay. No idea what that's all about. I'll try to load them again. You can always PM me with an email address and we can do it that way.
 
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286 to 486 kit (2nd attempt)

286 to 486 kit (2nd attempt)

Try this:
 

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