Cyrix M2 333, Underclocking and stuff

[TheCorm]

My Uncle currently has an ancient packard bell system, which he is looking to improve a little until he has the cash for me to build him a Duron based system. His system spec is as follows:

CPU: Intel Pentium 120
Memory: 40MB EDO Simms
Graphic: Cirrus Logic 2MB
Soundcard: Some Unknown Make
CDROM: 6x

The Motherboard is a PB640 which supports a max of 200mhz MMX Socket 7 CPU (the manual only mentions Intel).

Due to the difficulty of getting hold of a P200MMX, I thought I would try underclocking a Cyrix M2 333(250mhz) which I can get hold of down to 200mhz (66 x 3).

Would this be okay?, I presume you can clock a processor both up and down from it's default speed? Additionally, if the voltage selection is not great, the manual did not say much, as I am underclocking it would it run at 2.8v instead of 2.9v??

Any comments or opinions appreciated, cheers.
Corm

 

[Peter]

Try to find out who made the board.

Whatever you do, use a new MII from VIA manufacturing (labelled MIIv) - the older ones from IBM or NatSemi manufacturing have much higher power requirements, and probably won't run in that old thing.

With a new MIIv-300 (66 MHz 3.5x) chances are you can run it at its native speed, or step down to lesser multipliers as you please. These go for around $25. An underclocked MIIv-333 would also be fine.

2.9V support was also very common on those old boards. Look for it.

However, if PB used an Intel brand mainboard there, you're stuck. Intel has their mainboard BIOS written to deliberately not do anything with AMD or Cyrix processors.

Regards, Peter

 

[TheCorm]

I believe the motherboard was made by Packard Bell themselves, looking through the online manual, they only mention Intel processors, I'm starting to get a bit worried here.

Is there any chance I could get a bios update??

Mail me if you have any ideas on this,

Thanks

Email The Corm

 

[Assimilator1]

I don't suppose you live in the UK do you? getting hold of a Pentium 200MMX here is fairly easy ,say around £20-30 pounds for a 2nd hand 1.The Pentium will also have a much better FPU.

 

[TheCorm]

I do live in the UK but I have not been successful in finding either a Pentium MMX 166 or 200 in recent times.

Do you know anywhere I could get one, I am in west sussex. I only came up with the Cyrix idea because I could not get hold of an intel one.

Thanks,

Corm

 

[Assimilator1]

You need to buy a magazine called Micro Mart & scan their free adds ,it comes out weekly, or you can go to their website here.
Seriously ,Pentium 200 MMX's are 2 a penny in there ,I really wouldn't bother with a Cyrix.

BTW I'm in Guildford ,Surrey & I have a Pentium 166 MMX for sale ,though I would of thought you'd want to stick to a 200MMX ,are you sure it won't run a Pentium 233MMX ? (1.5x multiplier is used as to select 3.5x on those boards capable)

 

[TheCorm]

the online manual says it only supports up to 166mhz (2.5x66) but the paper manual says that it can handle 3.0x66 and Pentium overdrive/MMX processors, what did you mean by?:



<< (1.5x multiplier is used as to select 3.5x on those boards capable) >>



There is also something on the board called a CELP socket, that uses Cache On A STick technology, can you get these anyway (adds 256 - 512KB of L2 cache to the board).

Thanks,

Corm

 

[Assimilator1]

Motherboards that supported the Pentium 233MMX used the 1.5 multiplier setting to select the 3.5x multiplier in the Pentium 233 MMX cpu.Your Uncles board might do this too.
BTW have you looked at the website for the m/brd ,it might have more info than either manual.

I'm afraid I would have no idea where to get extra L2 cache ,except perhaps in 2nd hand adds ,but it's very rare.

 

[shiner]

Underclock a Cyrix CPU? Is that possible? I didn't think CPU's could run in reverse!

 

[Deathwish2000]

Yes it is possible to underclock a processor and in some circumstances it is necessary to!

 

[shiner]

It was a joke...you know...humor.....I meant that the Cyrix chip is alrady so slow that if you attempted to underclock it the thing would be so slow it would run backwards.

 

[TheCorm]

Turns out that the board ONLY supports Intel CPU's, damn intel and their system bios :|

But, thankfully, Assimilator1 has offered me a Intel P166MMX, which as he pointed out will have a better FPU than Cyrix anyway.

Thanks for all the help.

Corm