386SX wrote:

Hi, considering the Cyrix - Ti upgrading solution did a socket adapter ever exist to put a 486 maybe the lower models onto a 386 socket? bye

The Cyrix Cx486DLC is one example. I've done write up on this processor here: http://www.philscomputerlab.com/cyrix-486dlc.html

Some benchmarks:

Not any real 486es, probably because a 486 (even an SX) has the FPU integrated, so it will have a different interface to the system than a 386 does.
So you probably need a specialized CPU, such as the Cyrix ones (they are specifically designed to work with the 386DX bus, and support a 387DX-compatible FPU).

Scali wrote:

Not any real 486es, probably because a 486 (even an SX) has the FPU integrated, so it will have a different interface to the system than a 386 does.
So you probably need a specialized CPU, such as the Cyrix ones (they are specifically designed to work with the 386DX bus, and support a 387DX-compatible FPU).

Maybe 486SX has integrated FPU, but it's disabled or non-working - i.e. not present.

Otherwise only Cyrix/TI solutions exist to upgrade to "486" performance. Fastest would be Ti486SXL2-66 (PGA-132 socket)- 8kb internal cache and double the clock - it isn't compatible with all 386 motherboards though.

kixs wrote:

Maybe 486SX has integrated FPU, but it's disabled or non-working - i.e. not present.

Yes, but a 486SX is really just a 486DX chip, so it has the same pinout.
It cannot communicate with an external FPU. Instead, if you put a '487DX' in your system, the entire 486SX is bypassed, and the 487DX is really just a 486DX.
So it's not the same type of bus as a 386/387 system.

philscomputerlab wrote:

The Cyrix Cx486DLC is one example. I've done write up on this processor here: http://www.philscomputerlab.com/cyrix-486dlc.html […]
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386SX wrote:

Hi, considering the Cyrix - Ti upgrading solution did a socket adapter ever exist to put a 486 maybe the lower models onto a 386 socket? bye

The Cyrix Cx486DLC is one example. I've done write up on this processor here: http://www.philscomputerlab.com/cyrix-486dlc.html

Some benchmarks:

The boost is quiet amazing. I've one TX DLC to test I'll see. What was the difference beetween the SXL version and DLC?

Sorry, not sure. This is the only 386 upgrade chip I have.

philscomputerlab wrote:

Sorry, not sure. This is the only 386 upgrade chip I have.

No problem. Cause everytime I search for the latest upgrade solution, I find somethin faster to search again... 😁

1. There are sockets that carry a normal 486 168-pin cpu to put on a 132-pin 386 socket. Compaq made them, maybe in cooperation with Kingston, but I'm not sure.
2. The SXL has full 8KB L1 cache opposed to just 1KB L1 cache in the DLC CPU's.
3. There are clockdoubler chips for the 132-pin 386 socket. The 1KB DLC has the DRx2 (Cx486DRx2) variation and the faster 8KB SXL has the SXL2 (Ti486SXL2) variation.

I have all these CPUs and adapters and I suggest you to use a real 486 platform if you want to use a common 168-pin 486 CPU.
If you like more exotic solution like I do, get an old 386 board and pimp it with some DRx2 or better SXL2 chip.

I've read somewhere that a 386 clocked 50Mhz was scheduled but not released. Is it true?

FGB wrote:

1. There are sockets that carry a normal 486 168-pin cpu to put on a 132-pin 386 socket. Compaq made them, maybe in cooperation […]
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1. There are sockets that carry a normal 486 168-pin cpu to put on a 132-pin 386 socket. Compaq made them, maybe in cooperation with Kingston, but I'm not sure.
2. The SXL has full 8KB L1 cache opposed to just 1KB L1 cache in the DLC CPU's.
3. There are clockdoubler chips for the 132-pin 386 socket. The 1KB DLC has the DRx2 (Cx486DRx2) variation and the faster 8KB SXL has the SXL2 (Ti486SXL2) variation.

I have all these CPUs and adapters and I suggest you to use a real 486 platform if you want to use a common 168-pin 486 CPU.
If you like more exotic solution like I do, get an old 386 board and pimp it with some DRx2 or better SXL2 chip.

I'll go for the alternative solution, I'll search for the SXL2 one. 😁

386SX wrote:

I've read somewhere that a 386 clocked 50Mhz was scheduled but not released. Is it true?

I don't know if it were not just rumors.
At least it never has been released. Intel said bye bye to the platform @33MHz amd AMD established the nice budget niche with its 386DX/40 part and could compete with 486SX/25.
50MHz parts for the 386 platform exist, but only as clock doubled parts with an internal multiplier (as mentioned in Nr. 2 in my previous post).

FGB wrote:

I don't know if it were not just rumors. At least it never has been released. Intel said bye bye to the platform @33MHz amd AMD […]
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386SX wrote:

I've read somewhere that a 386 clocked 50Mhz was scheduled but not released. Is it true?

I don't know if it were not just rumors.
At least it never has been released. Intel said bye bye to the platform @33MHz amd AMD established the nice budget niche with its 386DX/40 part and could compete with 486SX/25.
50MHz parts for the 386 platform exist, but only as clock doubled parts with an internal multiplier (as mentioned in Nr. 2 in my previous post).

Thanx! It would be nice to have a real 50Mhz clocked 386. I am trying to build a very fast 386 with time correct components.

Some people overclocked their AMD DX/40 to 50MHz with changing the crystal. But that is not always succsessful because the CPU, chipset, memory and possible onboard cache must cope with the extra 10MHz bus speed. And even if the system runs at 50MHz it still has no L1 cache and won't compete against the Cyrix / Ti parts.

The safe bet would be to get a DRx2 or SXL2 and put it on a solid motherboard with a proper chipset.

Intel made the RapidCAD. I don't know anything about it other than what wiki says.

zstandig wrote:

Intel made the RapidCAD. I don't know anything about it other than what wiki says.

Haha, apparently they had to make two chips, one for the CPU and another 'dummy'(?) one in the FPU socket.

386SX wrote:

philscomputerlab wrote:

The Cyrix Cx486DLC is one example. I've done write up on this processor here: http://www.philscomputerlab.com/cyrix-486dlc.html […]
Show full quote

386SX wrote:

Hi, considering the Cyrix - Ti upgrading solution did a socket adapter ever exist to put a 486 maybe the lower models onto a 386 socket? bye

The Cyrix Cx486DLC is one example. I've done write up on this processor here: http://www.philscomputerlab.com/cyrix-486dlc.html

Some benchmarks:

The boost is quiet amazing. I've one TX DLC to test I'll see. What was the difference beetween the SXL version and DLC?

I think that DLC means that it is a DX processor with large cache.
I think that SXL means and SX processpr with large cache?

Having the FPU on chip absolutely was not an issue for getting the 486 onto the 386 bus. The Rapidcad was essentially the i486 core with the 8kb cache removed. Internal cache however is a serious problem on the 386 bus, because the original specification did not include an control lines for keeping the contents of internal cache up to date. Even the Cyrix DLC chip has problems with this on many 386 motherboards.

There are many socket adapters which allow you to attach a 168-pin 486 to a 132-pin 386 socket. I would guess at least half a dozen manufacturers made them, and on top of that each made various models. I happen to have one called "Transcomputer T486HPi", however I can't get the internal cache working on my 386 board because I don't have a way to hook up the cache control line to my cache controller.

Anonymous Coward wrote:

Having the FPU on chip absolutely was not an issue for getting the 486 onto the 386 bus. The Rapidcad was essentially the i486 core with the 8kb cache removed.

The RapidCAD is TWO chips, not one.
The second chip is a 'dummy', which is required for some signaling on the 386 bus:

Because the i486DX has a working on-chip FPU, a dummy FPU package is supplied to go in the Intel 387 FPU socket. The dummy FPU is used to provide the FERR signal, necessary for compatibility purposes.

That is the issue I was talking about.

Also, according to this page: http://www.cpushack.com/RAPIDCAD.html
It is not a full 486, it only has the 386 instructionset, not the new instructions such as BSWAP. I wonder why that is.

I also wonder how the other adapters handled the FERR signal. You could make a single-chip solution and have something plug into the FPU socket with some ribbon cable perhaps. Or perhaps they just disabled the FPU?
It seems that there is one here which has something to plug into the FPU socket: http://www.vintage-computer.com/vcforum/showt … board-386/page3

Thought at one time about trying this myself but that was before losing my original collection. Unless you have a nice system that you want to pimp out this is not worth it for the same reasons other people have already posted in this thread. If you want a 486 then build a 486 system, 386 is just fine for a lot of games of the era and you can look to other ways for a little extra speed if needed but the Cyrix SXL2 is nice if you get the cache working.