I think he means the 4x chips that don't have "4x" printed on them. They look exactly like non-4x chips, both for versions with and without OEM heatsink.

magicmanred wrote on 2024-07-30, 18:00:

Very interesting. Been trying to find a 4x variant. […]
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feipoa wrote on 2024-07-30, 15:16:

You definitely need to run some Quake and Windows tests to unfold all the issues awaiting you with Cyrix 5x86 -100 and -120 chips marked at 4x when operating at 133 MHz. Your best chances for stable 133/4x operation are with the non-speed marked chips with 1996 date codes.

Very interesting.
Been trying to find a 4x variant.

What do you mean by non-speed marked?
Can you post an example image?

Do you mean something like this:
https://cdn.cpu-world.com/CPUs/5x86/S_C ... speed).jpg

Yes, aside from 133/4x marked chips, that CPU you've shown has returned the best luck with for 133/4x operation, as long as the datecode is from 1996.

feipoa wrote on 2024-07-30, 15:16:

You definitely need to run some Quake and Windows tests to unfold all the issues awaiting you with Cyrix 5x86 -100 and -120 chips marked at 4x when operating at 133 MHz. Your best chances for stable 133/4x operation are with the non-speed marked chips with 1996 date codes.

Just got around to it, my -100gp and two -120gp chips all seem to work great at 133. Tested with Quake and Doom. I had lsser, fp_fast, and btb_en all enabled, no stability issues. This is also at the stock 3.45v. Active cooling is probably a good idea though. My passively cooled 120's (with OEM Cyrix heatsink) get a bit warm to the touch. However, my 100 with aftermarket heatsink and fan stays cool as a cucumber!

magicmanred wrote on 2024-07-30, 18:00:

Do you mean something like this:
https://cdn.cpu-world.com/CPUs/5x86/S_C ... speed).jpg

I wouldn't bother trying to find one of those blank ones. I've never seen one myself, and I've collected a lot of Cyrix 5x86's over the years. I own three 4x chips, and know a guy who owns another two. All of them are marked -120gp or -100gp.

willmurray461 wrote on 2024-08-02, 22:15:

I wouldn't bother trying to find one of those blank ones. I've never seen one myself, and I've collected a lot of Cyrix 5x86's over the years. I own three 4x chips, and know a guy who owns another two. All of them are marked -120gp or -100gp.

Thanks for the tip!

Are you, or anyone you know selling one? Would love to have one to tinker with on my ASUS PVI-486SP3.
I use a PCI Voodoo1 Display card paired with a VLB 2MB Tseng Labs ET4000/W32P, as well as an ISA AWE32 so upping the FSB much over 40Mhz may start being a concern.
But 33x4 would definitely be something that would agree with everything in my system 😁

I am currently doing 160Mhz (40x4) with an AM5x86 133ADW fully stable with 1MB MB cache, so 40Mhz fsb works great.

If I'm being completely honest, I don't think a Cyrix 5x86-133 is going to bring that much value to your system, especially since you already have a working AMD X5-160.

Also, market price for Cyrix 5x86-133's seems to be like $700+ 😬. If you find one on your own it won't be that expensive, but if you're buying from a collector expect to pay a lot.

In my opinion, 5x86-133's don't really make much sense in socket 2/3 systems, especially if they have 40MHz bus capability. If your 486 system is locked to a 33MHz bus and is not Pentium Overdrive compatible, then the Cyrix 5x86-133 has a decent lead over all the alternatives. However, in 40MHz or POD compatible systems, the Cyrix 5x86-133's lead diminishes greatly.

If you want to try out Cyrix stuff, it will be much cheaper to try to find a 120MHz model. The performance is very close to the 133 (and maybe even better in some scenarios due to the faster bus). Additionally, if you find an early -120GP (~week 42 1995 or earlier), there is a good chance it will be S1R3, meaning you can run branch prediction stable in Windows, which is impossible for the -133GP since it only exists in the S0R5 variety.

willmurray461 wrote on 2024-08-09, 18:58:

If I'm being completely honest, I don't think a Cyrix 5x86-133 is going to bring that much value to your system, especially sinc […]
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If I'm being completely honest, I don't think a Cyrix 5x86-133 is going to bring that much value to your system, especially since you already have a working AMD X5-160.

Also, market price for Cyrix 5x86-133's seems to be like $700+ 😬. If you find one on your own it won't be that expensive, but if you're buying from a collector expect to pay a lot.

In my opinion, 5x86-133's don't really make much sense in socket 2/3 systems, especially if they have 40MHz bus capability. If your 486 system is locked to a 33MHz bus and is not Pentium Overdrive compatible, then the Cyrix 5x86-133 has a decent lead over all the alternatives. However, in 40MHz or POD compatible systems, the Cyrix 5x86-133's lead diminishes greatly.

If you want to try out Cyrix stuff, it will be much cheaper to try to find a 120MHz model. The performance is very close to the 133 (and maybe even better in some scenarios due to the faster bus). Additionally, if you find an early -120GP (~week 42 1995 or earlier), there is a good chance it will be S1R3, meaning you can run branch prediction stable in Windows, which is impossible for the -133GP since it only exists in the S0R5 variety.

Very good points. I can definitely see what you're talking about.
I do have a Cyrix 5x86 100GP sitting on my shelf on display. Haven't popped it in to play with. I felt like it would be worth maybe selling it and getting a 120 to play with, but maybe I'll pop it in and see if it can do 40x3 and/or branch prediction.

1993 IBM PS/1

Specs:
486dx2-50mhz
32mb RAM
64kb cache
IBM IDE hard drive

I'm getting back again to tinkering with my old 486 motherboards and really love this benchmark!

Finally was able to get SpeedSys to run on the PS/1 2033 upgraded to a DX4-100 using an ODP:

Considerable upgrade vs the same CPU running at 75Mhz with the 25Mhz FSB:

Stock Pc Chips M912 with stock AMD 5x86 133 (4x33), no heatsink and modded 2x16Mb (EDO to FPM w parity). Nothing out of the ordinary.

I could manage to max out my Isa ide performance further on my 386sx board w/ TI486 CPU