Cyrix MII 333


Mauna Loa

New Member
Has anyone had much experience with this chip? How fast can it be overclocked? I am new to overclocking.

My mainboard is a Soyo 5EHM Super 7, with the ETEQ82C663 chipset. The CPU bus clock can be set at 66, 75, 83, 95, 100, 112 & 124 mhz and can be multiplied to 5.0.

Cyrix recommends 75 mhz bus at 3.5x, so if I am understanding this right, the CPU is running at 262.5 mhz (?).

I know the only way to do it is to just play around with different setting and see which one works. But clearly I don't want to do something like 124 mhz at 5.0x! Where would be a good place to start?

Also, I understand that the system can run unstable at certain bus speeds. I am currently having problems with freeze-ups and inadvertent rebooting. I thought it might be an overheating problem so I have ordered a cpu fan recommended for this chip.

I am new to a lot of this, any help would be appreciated.


New Member
Sadly, even at .25 microns, the Cyrix architecure is limited to, at most, about 300mhz (on average...ive heard some crazy cases, but this is the normal limit). You might try 2.5x100mhz if you have PC100 ram or your mobo can run the memory at 2/3 FSB, this is the setting for the PR 366. With your cache running at 100mhz, its sure to be faster. 2.5x112 or 3x100 would probably be the absolute best you can do, if your ram and the processor can handle it. Remember, increasing the bus is better than increasing the multiplier, as your cache also runs faster. Often, clocking the processor slightly lower with a faster FSB results in higher performance

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[This message has been edited by MadCat (edited 08-03-99).]


New Member
I had a MII 300 (75*3) for a while, and have just sold it on. Between buying my new super socket 7 and getting a new K6 to go in it I was able to reach speeds of up to 380.

I did this by
a) getting a huge fan heatsink combo,
b) A case fan
c)putting all the voltages as high as my mother board would allow (3.6 I think)
d) clocking to 3*100.

this wasn't paticulary stable though and I usually used 3.5*83 which was sold. this reported the CPU as a 366

hope this helps, just remember cool cool cool - the MII is HOT

Andrew Scott


New Member
Well, I just bought an MII 333 for an old mobo so I could get a second 'puter up 'n' runnin'.
It had 83x3 marked on the CPU, but that didn't seem to make sense as I thought it was a 333Mhz chip, not a 249Mhz as the markings were sugesting. What I didn't realise was that the MII's just use the Pentium Rating in the name of their chips, ie. Cyrix MII 333 PR, and it's actually a 249Mhz chip.
So, I thought I'd set it to 333Mhz (95x3.5). And it's been working at 333 very happily ever since. Though it is very warm!
I'd like to have a try for 350Mhz once I get it back from a friend who's borrowing it, because another friend has one running at 350Mhz too.
So, if you're lucky, they are actually overclockable. Just don't be too disapointed if you can't o/c yours.

Keep On Rockin' 'n' Overclockin' ;-)