General discussion


Locked FSB speed

By cioby_sv ·
Hi, I have an old Compaq Deskpro EN 6350 computer, with a PII (Deschutes) 350 MHz processor, chipset Intel 82440BX/ZX, FSB 100 MHz, 192 MB SDRAM and I would like to overclock to work at 500 MHz. BIOS is updated to the last revision 08/22/99. On my motherboard there are 6 switches for setting the FSB at higher speeds, and I have turn them on to run at 500 MHz, but nothing happened. It's seems that my motherboard has the FSB locked. Any ideas how to unlock the FSB setting?

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by TheChas In reply to Locked FSB speed

Have you tried the over-clocking web sites?

To be honest, PII boards in general, and OEM boards like Compaq are not apt to still be listed on all but the oldest sites.
Most tweak and over-clocking sites concentrate on the latest generation of AMD CPUs.

First off, your motherboard would have only 2 Front Side Bus speed options:
66 MHz for Celeron Processors and first generation PIIs.
100 MHz for all other PIIs.

The speed you can set with the jumpers is the CPU clock, as a multiple of the FSB.

Intel did lock the CPU speed setting for the PIIs because of problems with unscrupulous dealers remarking earlier Pentium CPUs with the faster speed they would run at on a test system.

I believe that you can use the jumpers to set a lower CPU clock for testing and compatibility.

Even if you do get it to clock at 500 MHz, you won't see a lot of improvement in performance.

I would take a look at some of the web sites that sell older PC hardware such as and
Both should have used PII CPUs for under $20 US.

I just checked the Geeks, and they have 2 different PII 450 MHz CPUs for under $11 US.


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by dmiles In reply to Locked FSB speed

1. I think PII's are multiplier locked, so you can only use the FSB (Correct me if I'm wrong, but I thought Intel did this aroudn the PII's time).

2. If you're at 66 mhz FSB right now, say at 333 mhz. A 83 FSB would raise you to about 415 mhz, close to the top for a PII.

3. I have no clue on the max temp for a PII, but a great place is The peopel there are nice. Anyways, slot coolers seem to be pretty cheap. You got a single fan setup? You can get dual fan setups for less than $10 sometimes.
Aksi see

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by cioby_sv In reply to Locked FSB speed

You're right it's the the clock multiplier that's have been locked not the FSB. FSB is set to 100 MHz not 66 MHz.
Thanks for the answer.

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