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P55c at Overclocked to 300mhz?

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First post, by prophase_j

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Hey Yall!

So I recently picked up an inclining to build a sick Pentium MMX system. I decided I wanted to have a real "classic system" so I could really remember what kind of gear I used to play with, and provide a different experience from what I get from my "Retro Rocket".

Originally I was going to build it around a Pentium Pro setup, but couldn't decide if I should use the original PPro or an Overdrive. Even if the overdrive seems like a logical choice, it just seems almost too fast for what I wanted to do. Because if I'm at that point, might as well get a real Pentium II. Noise made by those pesky little fans didn't help my decision.

I also contemplated a Socket 5 setup but I figured it would be hard to find a good one. Between Baby AT or ATX, built in cache or CoAST, it seemed really daunting. The old memory tech and bandwidth would surely slow me down too, since there is no SDRAM.

So from there, I contemplated strapping a Pentium Pro to a BX with one of those "slot-ket"s. At first I got really excited about this, with the BX memory controller and even picking up an AGP slot. I later found out that A)the original PPro likely won't work and B)A 400mhz PII would likely eat the overdrive, and be quiet!!

It was then that I remembered that Socket 7 can use the classic or MMX Pentiums, have SDRAM, and are a lot more available. A 233 Pentium MMX sounded pretty nice, it just had a ring to it.

So after some research, I have decided to go with a MVP3 based board. I know everyone and their mother hates VIA, but I haven't had the horrible luck or misfortune I have read about. I understand them to have better performance then the ALi's or Intels. I Know the AGP is a joke, but I figured I wouldn't throw anything more powerful then a TNT2 in here anyway.

Right now the main contender is a FIC PA-2013, it looks like it has a manageable layout, SDRAM, and the 2mb L2 cache is just icing on the cake. I plan on getting a Diamond Stealth 2000 and a vintage Voodoo 1 for video, ideally a Vibra based SB16 with a real OPL3 and daughterboard.

So now to the real question, how can I get the Pentium MMX to 300? I saw a random post that mentioned it, and have been intrigued since. Has anyone here ever done this before? What chip do I need to get a 3x multiplier.. I assumed that the proper combination would be 100fsb x 3, but what I have read is that 233 has a 3.5. I'm also curious as to what kind of cooling would be necessary.

"Retro Rocket"
Athlon XP-M 2200+ // Epox 8KTA3
Radeon 9800xt // Voodoo2 SLI
Diamond MX300 // SB AWE64 Gold

Reply 1 of 225, by retro games 100

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Unfortunately, I'm not knowledgeable enough to help you with your "real question" about the MMX -> 300, but I enjoyed reading your post, to see how you were working out what stuff to mess about with. So, all I can say is - good luck! 😀

Reply 3 of 225, by 5u3

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Why not take a K6(-2/-3)? Perfect match for that board and much more versatile than an P55C because of open multipliers.

You'd have to be very lucky to get a Pentium MMX running at 100 MHZ FSB. Even 83 MHz is quite a challenge (e.g: P233 @ 83x3.5).

Reply 4 of 225, by elfuego

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5u3 wrote:

Why not take a K6(-2/-3)?

Because they suck? 😜 Sorry, but now that I've tested K6, K6-2 and recently K6-3 ranging from 266Mhz to 600Mhz I can tell that those CPUs are nuisance when compared to genuine Intel of that time. The only good thing about K6 is, as you already mentioned, ability to run from 120Mhz to 600Mhz, in a setting you choose.

But on the performance side - there is only Intel.

Reply 5 of 225, by Silent Loon

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There were some faked pentium 266mmx tillamook labled "Pentium MMX 300" from Taiwan. I suggest they are very rare. You will find a picture and short description of it here: http://www.cpu-collection.de/
(look up the 586 / Pentium / K5 section)

Reply 6 of 225, by Anonymous Coward

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I have one of those 266MHz Pentium MMX chips. I didn't think they were all that rare. A few years back sellers were unloading them on ebay. I think they were all desolders. My bigger problem is finding a motherboard that supports them. From what I can tell, they will only work on systems with Intel TX chipset. In addition to that, you also need support for some pretty low voltages.

If you want to clock at 300, then the 266MMX is probably your best bet. I think there is also a 300MHz version, but all the ones I've seen are proprietary BGA modules.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 7 of 225, by swaaye

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I have gotten a P233MMX to 300 MHz. On a Super 7 board at 100 MHz FSB x 3. It wasn't entirely stable but it was close.

I like K6-III more though because its L2 cache makes a sys feel so much snappier. Of course, it's still a terrible CPU for 3D games..... 😀

Reply 8 of 225, by ih8registrations

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The K6-x fpu is around half the performance if I recall, so if you can get it running at 600 MHz, you're matching the PMMX @ 300 FPU-wise, and should be faster overall from the much faster integer performance.

Reply 9 of 225, by swaaye

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ih8registrations wrote:

The K6-x fpu is around half the performance if I recall, so if you can get it running at 600 MHz, you're matching the PMMX @ 300 FPU-wise, and should be faster overall from the much faster integer performance.

Yeah I had friends who were running K6-2 450s back in the Unreal Tournament times. My Pentium III 450 was much faster. In fact, I think that my P2-266 was about a K6-2 450's equal in 3D shooters.

Reply 10 of 225, by prophase_j

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Yeah I used to have a K6-2 400 back in the day, and I remember my friend having a Pentium II 333 and it keeping up and sometimes beating mine. Still leaves a bitter taste in my mouth.

@Swaaye: Why am I not surprised the you've had a 300mhz PMMX? 😉 Do you have any more insight here? what kind of board were you using? How about cooling?

I was reading a review about the PA-2013 2mb and they were saying that it wasn't 100% stable as the predecessor. It locked up a few times at 100mhz bus speed with properly rated K6's, and the 112mhz setting that previously worked was a no-go. They blamed it on mediocre cache chips, and with double the size you have double the likelihood of errors. If any one has experience with this board I'd like to hear about it. I could defiantly live with just 1mb.

I'll also say that the PMMX project is defiantly going to happen. Having it run at 300mhz will be super cool but by no means is a deal breaker. So if I'm only running the stock bus speeds with it I figured the cache might stabilize and the world could be happy.

"Retro Rocket"
Athlon XP-M 2200+ // Epox 8KTA3
Radeon 9800xt // Voodoo2 SLI
Diamond MX300 // SB AWE64 Gold

Reply 11 of 225, by elfuego

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ih8registrations wrote:

The K6-x fpu is around half the performance if I recall, so if you can get it running at 600 MHz, you're matching the PMMX @ 300 FPU-wise, and should be faster overall from the much faster integer performance.

I did say K6s suck, but lets not over do it. K6-3 running at 600MHz (5.5x120, or 6x100Mhz) has comparable performance to Celeron @ 450 Mhz. Tested on Voodoo 5 5500 and 3dmark 2000. Running it on default though, (@400 Mhz) produces much the same results as PMMX 266-300Mhz = very crappy.

What's really going on my nerves is the fact that I can run Super 7 mobo at 120Mhz FSB, with equally overclocked RAM and it still produces mediocre results. Theoretically, it should be able to leave Celerons and some P2's in dust couse of its FSB/RAM/tact, but it simply doesnt. 🙁

Reply 13 of 225, by prophase_j

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I'm really not planning to fool around with the K6 much. If the board I get supports it, I might get one just to have, and swap it to compare against things, but my target for this machine is to have a "Minimum Requirements" platform, to match the specs for a lot of the games I play. That's why the speed isn't a major concern. I wanted to get the 2mb cache model since it will cache up to 508mges of system ram, as opposed to the 254 of the 1mb model. I'm planning on building a Camino-Coppermine based P3 later, and my "Rocket" for the most part runs flawless and it can go from 600mhz all the way 1.67ghz wth the BIOS and a single jumper.

"Retro Rocket"
Athlon XP-M 2200+ // Epox 8KTA3
Radeon 9800xt // Voodoo2 SLI
Diamond MX300 // SB AWE64 Gold

Reply 14 of 225, by swaaye

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ih8registrations wrote:

It comes down to the FPU.

That's a big part, but I think there's also the issue of Socket 7's horrible L2 cache and memory performance. PPro/Pentium II and up have a backside cache bus and a superior chipset in general (if you go Intel) so they have better memory performance.

Of course, K6-III has the backside cache bus too, but it still has a gimpy FPU and rather horrible RAM performance. And poor AGP performance as well considering those Super 7 mobos. You can't trust those boards to work with GPUs with T&L. Voodoo5 is about the best choice there is for Super 7.

Reply 15 of 225, by swaaye

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prophase_j wrote:

@Swaaye: Why am I not surprised the you've had a 300mhz PMMX? 😉 Do you have any more insight here? what kind of board were you using? How about cooling?

I have managed to build up a little Pentium MMX collection from old hand me down computers. One day I decided to see if the FIC VA503+ mobo I had could get one to 300MHz on 3x100. Any Super7 mobo should work. You just need that 100 MHz FSB support.

They don't get very warm and I had a decent Socket A cooler on it. Upped the core voltage a bit from the stock 2.8v. And there it went.

Reply 16 of 225, by ih8registrations

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>You can't trust those boards to work with GPUs with T&L.

A remote chance I'm wrong, but I think I'm safe to say that's not correct.

Interesting that there are AGP versions of the latest gen GPUs: http://www.fudzilla.com/index.php?option=com_ … =1&limitstart=0

Here's some interesting threads talking about the cpu limitations from using these cards on older systems:

http://forums.anandtech.com/messageview.aspx? … hreadid=2245151

http://www.hardforum.com/showthread.php?t=1276019&page=6

Last edited by ih8registrations on 2009-03-28, 20:59. Edited 1 time in total.

Reply 18 of 225, by ih8registrations

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It would be AGP 4x/8x, which is fine as there are 4X, if not 8x, super7 boards.
Mind you, even though newer GPUs offload more, they need a strong enough cpus and bandwidth to keep them fully fed, which a k6/s7 system wouldn't come close. As the threads I added show, even xp & p4 systems fall short of providing all the video card could take.

Reply 19 of 225, by gerwin

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AGP 4X on a super socket 7 board, that would surprise me... Interesting to see an ATI Radeon HD 3850 as an AGP model. Wikipedia stated that nvidia AGP versions would end already with the 7 series (I am glad they still made the Geforce 7600 GS for me)....