One more. I have a matched pair of these.

Did the 586 or 686 fit in 486 sockets? were they worth a damned or crap (slower than intel 486).

The Cyrix 5x86 was faster than the Intel 486. Refer to the Ultimate 486 Benchmark Comparison. They work in a standard 486 socket 3.

feipoa wrote:

Attached are some less common, harder to find, or rare chips in my collection.

The AMD DX2 shown can actually run at 166 MHz, that's 2 x 83.33 MHz.

Oh, stop! You and your Cyrix chips. LoL! 🤣

Incidentally, does anyone have one of the recalled 1.13ghz Pentium III chips? I would think that would be one of the rarest CPU's to have. It would be nothing more than a wallhanger because of all the bugs, but still nice to have as a collectible.

I think the rarest is the 486slc that's in the IBM PS/2 Model 30-286. It was a very niche processor, mainly aimed at laptop manufacturers that wanted 486 speeds without creating a fully 32-bit bus or going with a 386sx. The second most rare is probably the Intel 387 and AMD? or Cyrix? coproessor that we put in the same 30-286. We had to pull the coprocessor out when we instaleed the 486slc though.

Samir wrote:

I think the rarest is the 486slc that's in the IBM PS/2 Model 30-286. It was a very niche processor, mainly aimed at laptop manufacturers that wanted 486 speeds without creating a fully 32-bit bus or going with a 386sx. The second most rare is probably the Intel 387 and AMD? or Cyrix? coproessor that we put in the same 30-286. We had to pull the coprocessor out when we instaleed the 486slc though.

The Cyrix 287XL+ was pretty rare. It's probably the most capable of all the 287 class FPU's and very hard to find. LZF7000 has had one for sale for a while now, but his price is high and he's the only one I've ever seen who had one.

sliderider wrote:

Samir wrote:

I think the rarest is the 486slc that's in the IBM PS/2 Model 30-286. It was a very niche processor, mainly aimed at laptop manufacturers that wanted 486 speeds without creating a fully 32-bit bus or going with a 386sx. The second most rare is probably the Intel 387 and AMD? or Cyrix? coproessor that we put in the same 30-286. We had to pull the coprocessor out when we instaleed the 486slc though.

The Cyrix 287XL+ was pretty rare. It's probably the most capable of all the 287 class FPU's and very hard to find. LZF7000 has had one for sale for a while now, but his price is high and he's the only one I've ever seen who had one.

I can't remember if that's the model we have or not. I know we had an Intel one that was good for even 386's (so we kept it in when we upgraded to a 386slc), and then a Cyrix one that worked only with 286's, but was much faster.

Shoot, I forgot we had upgraded this system twice--so we have a 386slc upgrade chip that would make the 286-10 around 386sx-15/20. It was double the speed for us, and we could finally run Win 3.1 in Enhanced Mode for true multi-tasking.

I just purchased a large lot of 70+ 386/486/586 class CPUs, mostly Intel, but some Cyrix and AMD.

Are some Intel 486 SX/DX/DX2 models more rare/collectable than others?

I'm not knowledgeable enough on the series to know their relative rarity compared to other same-era processors, but according to my observations, the least common CPU I have in my collection is a Cyrix MediaGX 180MHz. I actually have two of them, one in a working system and one from a dead system.

I don't think MediaGX CPUs are rare, nor are they particularly sought after, especially non-PGA chips. The MediaGX chip to have, which is very rare, is the GXm-300.

There are a few Cyrix CPUs in the lot, including one of these. What kind of socket/motherboard will it fit? Not Socket 3, right?

I already have a Cx486 DX266 and a 5x86 120GP with the green heatsinks (my brother-in-law used to work for Cyrix in the early 90s).

The chip in that photo works in a Socket 3 motherboard. The Cyrix 5x86-120GP with the green heatsink was less common, but not rare.

What did your brother-in-law do for Cyrix? Which years?

feipoa wrote:

The chip in that photo works in a Socket 3 motherboard. The Cyrix 5x86-120GP with the green heatsink was less common, but not rare.

What did your brother-in-law do for Cyrix? Which years?

He is a CPA, so I'm pretty sure he was in their accounting department. He really liked computer games back then. He was with Cyrix for a couple of years, probably something like '93-'95. He got me the CPUs I mentioned above, as well as a 6x86. The 6x86 came on a motherboard. I stll have the generic motherboard box with a Cyrix label on it. I have a heatsink fan with a Cyrix 6x86 label on it. Don't know what happened to the CPU or motherboard, however.

I'm almost positive that Cyrix used M-Technology motherboards. I think I had the M-Tech R407E with the 5x86. The 6x86 may have come with an R534.

Do FPUs count?
In my 386SX I had an IIT3C87SX:

It is compatible with the Intel 387SX, but more interestingly, it had an extended instructionset, and it actually had 3 stacks of 8 FPU registers instead of just one.
With this contraption you could put entire 4x4 matrices into the registers, and multiply with a 4x1 vector. There were special instructions for that.
This made it considerably faster in 3D mathematics than a regular Intel FPU. But I think they were quite rare, and not a lot of software took advantage.

Got two of these. Both NIB, but I recently unboxed one on my YT Channel 🤣

Just look how shiny it is!

I'm not much of a collector... but I do have around 200 processors from 8088 to Athlon 64.But I don't know if there are any really rare ones.

I'd like to find some Amd X5 150Mhz.. Also some K62 570.. or K63+550..
I got only common cpu.

boxpressed wrote:

I just purchased a large lot of 70+ 386/486/586 class CPUs, mostly Intel, but some Cyrix and AMD.

Are some Intel 486 SX/DX/DX2 models more rare/collectable than others?

The 486dx-50 (not dx2-50) was quite rare. This is because the clock ran at 50Mhz rather than being 25Mhz and then doubled internally. It was on par with the performance of a 486dx2-66.

The 486sx was an interesting animal that was much different than the 386sx. The 386sx used a 16-bit external bus with a 32-bit internally. The 486sx was actually a regular 486dx chip with a bad on-chip floating point, so that was disabled. The internal and external busses were still 32-bit.

boxpressed wrote:

There are a few Cyrix CPUs in the lot, including one of these. What kind of socket/motherboard will it fit? Not Socket 3, right? […]
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There are a few Cyrix CPUs in the lot, including one of these. What kind of socket/motherboard will it fit? Not Socket 3, right?

I already have a Cx486 DX266 and a 5x86 120GP with the green heatsinks (my brother-in-law used to work for Cyrix in the early 90s).

I'm not sure when the Cyrix P-series of chips came out, but those where pretty standard sockets. I know our supermicro motherboard was able to take either a cyrix p166 or an intel 166 chip, but the cyrix was 1/2 the cost and slightly better on integer performance, so we got the cyrix.

Scali wrote:

Do FPUs count? In my 386SX I had an IIT3C87SX: http://www.chipdb.org/data/thumbnails/930/IIT_3C87SX-20_diff_print.jpg […]
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Do FPUs count?
In my 386SX I had an IIT3C87SX:

It is compatible with the Intel 387SX, but more interestingly, it had an extended instructionset, and it actually had 3 stacks of 8 FPU registers instead of just one.
With this contraption you could put entire 4x4 matrices into the registers, and multiply with a 4x1 vector. There were special instructions for that.
This made it considerably faster in 3D mathematics than a regular Intel FPU. But I think they were quite rare, and not a lot of software took advantage.

That's a rare one alright! IIT made solid math coprocessor chips, but I didn't know they made extended instruction sets. I vaguely recall certain applications (cad, etc) that could take better advantage or recommended an IIT coprocessor vs intel, et al.

The Transmeta Crusoe should be a rare chip

The closest I can come is with my 600MHz Katmai and 900MHz Slot A Tbird.