Max verified 486 class overclock?

[RoadWarrior]

Hi guys,

I still mess with my older hardware, and I was going to get some calcium chloride to play with to get a -50c refrigerant solution to try and cryo-burn-in my XP,... anyway, so I started thinking about trying it out on my less expensive hardware first. Namely, my poor old Cyrix 5x86 chip. This is why this isn't in a CPUs forum, there isn't a cyrix one.

So, I have this board that will run a 60Mhz, bus, yes a 486 board with a 60Mhz bus. Do I need to repeat that again? Good. Currently I can run this chip with a 2x multiplier at 120Mhz and it gets very impressive benchmark results for a 486 class machine, almost as good as the 6x86 @ 2x60. So if I try my refrigerant on it, I might get it running on a 3x multi at 180Mhz @ -50C.

I haven't seen any verified 486 class overclocks this high, so was wondering if this might get a "record".

I've seen that joke "vodka cooled" 486 overclock by the way. And several more joke 486 overclocks, I'm wondering about the real deal.

I have a suspicion that the clock multi on that board also may have at least a 66Mhz clock as well as a 75Mhz clock on as well. However these don't run of course, but while I'm messing, I could stick a pot of coolant on the "northbridge" . . . . . . . . .

I think I will have a play with one of those BIOS editors though, see if I can figure out how to extend the memory and cache wait states and timings, after all this uses the same RAM and cache as some pentium boards, which just have more wait states.

I'm pretty sure that the core technology in this chip is equivalent to that in the 6x86 and some people have had those up to 200 with pelts on, so this might be worth a go.

Oh, why try it on only a 486? Well, all of my other board and CPU combinations are maxed out, or pretty much so, don't have any nice 124Mhz socket 7 boards or anthing like that, this is the only one with enough spare o/c capacity to be an interesting experiment.

Yes I need a life

Road Warrior

 

[David]

I think that all 486 multipliers are set on the chip, but good luck with the overclock. I don't know the best overclock for that chip, but let me know how you get on. What is the speed rating for that Cyrix chip btw?

 

[RoadWarrior]

This is a 5x86 100GP, 100Mhz, so it's overclocked at 120, there was a 120 version, and an OEM 133 version that's very rare. It has 2x and 3x multipliers implemented, for 2x50 or 3x33 @ 100, the very rare 133, used in laptops I think and some upgrade chips, is locked at 4x I beleive. AMD enhanced DX4 and DX2 chips in the 3.3v versions also had a 2x/3x selectable multiplier, so you can o/c some Dx2/80s to DX4/100. Amd 5x86 chips had a 3x/4x selectable multiplier, but their rated speed of 133, is 4x33, so the 3x multi isn't much use on them. Some Cyrix enhanced DX2s and DX4s are meant to behave the same as the AMDs, there were never many around though. There was just multiplier pin in the later socket 3 and socket 6 specs, it could be pulled high or low to select a multiplier on chip. You are right in saying the majority of 486s had thier multiplier locked on chip. Another user of that pin is the Pentium overdrive. I think it could use 2.5x and 1.5x.

Road Warrior