P3 clock locked?

[Rhonda85]

Hi, I was wondering if the Pentium3 is clock locked like the celerons. Also, I have an Abit BH6 motherboard that I was going to put a P3-700 in. What is the best overclocking speed for this cpu?

Thanks, Rhonda

 

[bacillus]

yes, the p3 is clock locked.
If you have a cBO or cCO stepping p3, then x133fsb is the "ideal" o/clock but there's no telling if your chip will o/clock by that margin!

 

[spamboy]

bacillus is right, the PIIIs are all locked, and many 700's can hit 933 with the bus at 133. I would go for it.

 

[KR]

The PIII's are NOT "Clock Locked" and neither were the Celerons.

They are (as are the Celerons) MULTIPLIER LOCKED meaning that the chip is set by Intel to multiply the FSB (Front Side Bus) clock by a fixed number. ie; a PIII-700e (100 MHZ FSB) multiplies the 100 MHZ FSB by 7 to realize the 700MHZ internal clock rate.

The FSB clock can be varied from the default with your BH6's bios and many PIII 700e's are reaching speeds in excess of 900 MHZ by overclocking this way. There have been successful overclocks achieved by increasing the FSB by as much as 50% over default with the PIII's and in excess of 70% with the CeleronII's.

In a case where the clock is to be actually locked, the CPU would have to have the ability to recognize an input clock outside the normal FSB rate and refuse to function due to a non-standard clocking. According to some reports last year, Intel had experimented with adding this "feature" to their CPU's but at least for the moment have not chosen to do so. Probably due to other problems that this could potentially create, besides ending the opportunity to overclock.

Sorry if this seems like an exrcise in semantics but there is a big difference between clock locking and multiplier locking.

Though not by design, the T-birds and Durons are essentially clock locked due to current limitations of the motherboard chipset that supports them (soon to change with the release of the 133A chipset). Most users with the current chipset are finding that the FSB can only be increased to about 10% above standard. It's been discovered that the AMD multiplier locking approach allows a simple bypass to re-activate the user defined multiplier control and the greatest percentage of overclocking gain seen with the T-birds and Durons at present is by increasing the clock multiplier with a very small adjustment to the clock frequency.

Happy Overclocking!

 

[EvilDonnyboy]

yup, KR gots it.

 

[NOX]

<< The PIII's are NOT &quot;Clock Locked&quot; and neither were the Celerons. >>

Good one KR. When I saw the title I was wondering what the hell is clock locked, though that can only mean one thing right, no more FSB manipulation. :Q

Rhonda85,

Welcome to AnandTech's! We all learn some how, I know I did, and you will too. AT is a very informative spot.

 

[chasm22]

KR; Does the same thing apply to the PIII 800? In other words, can it be oc'ed in a fashion similar to the PIII 700?

Thanks

 

[NOX]

All locked processors can only be overclocked via Front Side Bus (FSB) handling.

For example,

P3 700 - 7.0<-(Locked Multiplier) x 100<-(FSB) = 700Mhz
P3 700 - 7.0<-(Locked Multiplier) x 110<-(FSB) = 770Mhz
P3 700 - 7.0<-(Locked Multiplier) x 133<-(FSB) = 933Mhz
P3 700 - 8.0<-(Unlocked Multiplier) x 100<-(FSB) = 800Mhz, and so on.

Though majority off all P3?s are locked, if you?re lucky you?ll find one that isn?t, which will probably an engineering sample.

 

[Sunny129]

the 750 or 800e is probably intel's next best pentium OCer b/c they both utilize the 100 mHz fsb by default. however, the OC percentage, or yield, is less than it would be on a 700e. your money is better spent trying to OC a 700e rather than an 800e.

 

[KR]

Yes, the PIII-800e can be overclocked (I'm running one at 936MHZ).

As was mentioned, the 700e still seems to be the favorite with the increase of 100 to 133MHZ putting it in the normal operating bus speed for peripherals with the Intel 815 and Via based motherboards and a very high percentage of these devices reach 933MHZ.

The 800e is a pretty good overclocker but the success at 133MHZ FSB is less achievable since 8 X 133.3 = 1066MHZ and the current process is not producing silicon that will regularly reach 1.06 ghz. Even Intel has pretty much thrown in the towel for producing PIII devices above 1 GHZ. Yes, some devices will run at higher speeds but the percentages are pretty low.

If you check the database at overclockers.com you'll find that somewhere around 70% of the 700e's, 750e's and 800e's reach speeds of ~950 MHZ. of these, perhaps 10% exceed 1 GHZ. So, it means that it's still a roll of the dice as to what you'll get if you buy an Intel device for overclocking. Chances are pretty good you'll get a 700, 750 or 800 to 933-950 but not quite 1 in 10 chance to exceed 1 GHZ.

When I upgraded from my trusty C300a@450 I wanted a guaranteed increase of performance of somewhere around 100%. The 800e at default achieved the 100% increase in performance over my overclocked celeron so even if it didn't overclock at all I was still where I was hoping to be speed-wise. The added speed that I was fortunate to get by overclocking is pure manna from heaven and even without it I'd be happy with my system performance. For me the 700e at default wasn't quite enough of an increase to justify the upgrade by itself and the cost difference was so small from the 700e to the 800e that the 800e was my choice. Yes, I could have purchased a guaranteed 700e@933 for a moderate premium but it would have been more costly than an 800e retail device. Like most who have upgraded from the C300a, I'm very pleased with the result.

As for overclocking the T-birds and Durons - It seems that 90%+ of these devices built on the .18 process successfully reach 900+ MHZ and most of these appear to exceed 1GHZ. I guess AMD has their fabrication process proooducing some very good silicon. Very impressive yields when viewed from the technical manufacturing aspect and what a treat for us overclockers. Hopefully AMD will continue to make the L1 links available for re-linking.