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Pentium 200mhz multiplier unlocked??

G

GT578

Senior member
I just got a pentium200mhz chip to replace a pentium100mhz in my computer/router. Its a Dell Optiplex and although Dell's website says it can take a pentium 200mhz when I opened the computer the pins where I'm supposed to put the jumpers on to clock it at 200mhz was never put on although the label is there. I just selected 166mhz and checked the bios...and it says its at 166mhz but i'm not totally sure that it is running at that speed. I read somewhere that classic pentiums are unlocked....is that true??
 
All Pentium processors, except for a very short experimental run of Pentium 133MHz processors, are unlocked.

Pentium MMX processors are usually multiplier limited, although some may be completely unlocked.
 
I seem to remember something different to this. I was on the team that implemented the lock (sorry guys) and I seem to remember quite a few more than just one S-Spec for a 200MHz part. We implemented it on 120, 133, 150, and 166 as well as I recall. But this was 6 years ago and I may be remembering wrong, so I will defer to the FAQ answer until I have time to go look it up. It wasn't a complete lock as we know it today. It was a restriction of valid multiplier choices so that you couldn't, for example, take a 133MHz part and run it at 166MHz, but you could run it, in this hypothetical example, at 120MHz.
 
If your bios says it's at 166, then the 200 is underclocked. AFAIK "classic" non-mmx cpus were unlocked and alot of the mmx were too. I used to have my 166 overclocked to 200. I usually just go one step up though when overclocking these old chips, so I would go 233 if you have a 200 cpu.
 
Patrick,

Since I don't actually have an P133 SY022, I can't verify if it is multiplier locked or limited. I know that most P55C Pentium MMX processors should be limited, and probably some very late Pentium 166s and 200s, although I have no concrete data on the P54s.
 
Andy, I had a P-133 (I can't recollect the marking, but I'll check it later), that was locked. I couldn't run it with a 2.5 multiplier (166Mhz), but I think it could run at 3x60 (180Mhz), but that was too high an overclock for it to take, especially since the HSF was pathetic. Intel had put this lock because many P-133s were o/clocked in machines, re-labelled and sold as P-166 machines, especially in Europe and Asia, IIRC. I think the P-133 was the first and then they also added multiplier locks on some later CPUs. AFAIK, these multiplier locks were only partial, i.e. they only disabled certain multipliers, but others remained enabled. So you could change the multiplier, but usually you had to make larger changes, thus making overclocking very difficult. I'm pretty sure that quite a few later P54s were locked too...I've definitely heard of P166's and P200's having this partial multiplier lock

Anyway...I still managed to overclock my P-133 to P-150, since I had a VIA VPX based motherboard that had a 75Mhz async bus (CPU + memory @75Mhz, PCI, ISA and USB @stock). Kudos to VIA 😎
 
I recall it being a partial lock - like ssanches mentioned. So it might appear to be unlocked until you tried several different combinations. It was implemented like ssanches said.

I'm sure of my facts that we implemented a change like this - I was one of the three people who actually performed the work to implement it on the P54CS product. I'm just not sure how many s-Specs this affected and exactly how it worked with regards to what was allowed and what was not. It was back in 1995-6 that I worked on this.

Patrick Mahoney
Microprocessor Design Engineer (who, a long time ago, worked on the P54CS version of the Pentium CPU)
Intel Corp.
 


<< I recall it being a partial lock - like ssanches mentioned. So it might appear to be unlocked until you tried several different combinations. It was implemented like ssanches said.

I'm sure of my facts that we implemented a change like this - I was one of the three people who actually performed the work to implement it on the P54CS product. I'm just not sure how many s-Specs this affected and exactly how it worked with regards to what was allowed and what was not. It was back in 1995-6 that I worked on this.

Patrick Mahoney
Microprocessor Design Engineer (who, a long time ago, worked on the P54CS version of the Pentium CPU)
Intel Corp. >>




Interesting. To bad my socket7 mobo's only go to a think a 3.5x? multiplyer. I was able to up the bus to 75mhz and put the multiplyer at 3.5x and get a nice little oc out of the 200mhz mmx and don't remember on the 166mhz mmx I have. 😀
 
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