I would just like to add that I once had an IBM 'Blue Lightning' 486DX2-80 CPU for Socket 3, which was a rebadged Cyrix Cx486 (earlier IBM 'Blue Lightning' 486DLC models were made for 386SX systems, and were not based on Cyrix, despite both using the 'DLC' name).
It seems IBM also sold rebadged Cyrix 5x86C CPUs.

I would also like to know why some Texas Instruments DLC CPUs have "TI" and some have "TX". That has been bugging me for a long time. I am pretty sure they are both identical internally and based on 1kb cache though.

The only difference I am aware of with ST 5x86s over the Cyrix/IBM ones is that they are mostly wired for the 3X/4X multiplier rather than 2X/3X. From what I understand they are not later revisions and overclock about the same as the Cyrix chips (not very well).

I have an ST 5x86. Overclocking was identical for me - as was everything else - but your results may vary of course.

I suspect the naming convention is just one of those things. Just think, when Intel brought out the 386 it wasn't called the 386DX. In the case of the Ti/TX486 it may have been some contractual/legal BS. Doesn't appear to be age related as the date codes are too close - in fact, they overlap. Perhaps it depends what fab they were made at? If they were making them at more than one, perhaps there was some reason for it such as a mechanical limitation or cost reducing measure that was taken? Either way, I can find no difference, if any of them are 8K versions my motherboard must be incapable of recognizing this - though I suspect they genuinely are all the same.

I thought Cyrix didn't have its own fabs, so they contracted other companies who had fabs to produce the chip for them, in exchange for letting them produce some for of these chips for themselves which they sold using their own markings.
Theres quite a lot written about it on the net. The 6x86 ST chips for instance were basically the Cyrix 6x86MX chips running at 2.9v, but they couldn't produce the MII chips running at 2.2v as this design was created after VIA had taken over or something.

I don't know the details, but I reckon it must have something to do with Cyrix being fabless and them letting the 'fabhaves' keep some of the chips they produced for Cyrix and sell them on their own, with their own logo's and such.

Anonymous Coward wrote:

The only difference I am aware of with ST 5x86s over the Cyrix/IBM ones is that they are mostly wired for the 3X/4X multiplier rather than 2X/3X. From what I understand they are not later revisions and overclock about the same as the Cyrix chips (not very well).

So, the ST 5x86 chips either run as 25 MHz FSB x 4 = 100 MHz or as 33 MHz FSB x 3 = 100 MHz?
Can you "force" 33 MHz FSB x 4 = 133 Mhz, or will that just end up in a "hung" system?

Many people have tried to overclock ST5x86 to 133, but it wasn't successful.