Dell Dimension XPS H Processor Upgrade Information
compiled by Robert Hancock
These systems (apparently) use a Dell OEM version of the the Intel PD440FX motherboard.
For reference, the list of changes in all Dell BIOS versions for this system is available here. If you have a BIOS version earlier than A03 and want to upgrade the processor, I recommend you upgrade to that version.
Processor upgrades on these machines are somewhat limited because of the limitations of the 440FX chipset used on these machines' motherboards. These machines and motherboards were basically a stopgap measure to get Pentium II systems out on the market quickly while the first "real" Pentium II chipset, the 440LX, used in the D-series machines, was released.
The FX chipset only supports 66 MHz bus, so the fastest Pentium II you can use is 333 MHz. This page on Intel's site lists the jumper settings that you have to use to set the CPU speed properly for the processor you are using (these processors are old enough to not be multiplier locked, so the CPU speed cannot be autodetected like with later systems).
It is possible to upgrade these machines to a faster Celeron processor, but there are some complications.
Like the D-series machines, these machines will not support the low core voltages that the newer Celeron II CPUs require, and so a voltage regulating slocket will be required to run these at the right voltage. See the D-series page for more info on this.
Secondly, the BIOS seems to have some problems with the L2 cache on the processor. I received the following information from Powerleap concerning this upgrade using their PL-iP3 voltage regulating slocket:
With the PL-iP3/766 upgrade installed, when the system starts to boot, the BIOS displays an error message:
Cache Memory Failure. Do not enable cache.
Press <F1> for setup, <ESC> to boot, <F2> for option ROM Screen.
However, pressing the <ESC> key allows the system to boot, and the 128 L2 cache is enabled and working. I think the BIOS is inadvertently assuming that the CPU is a Pentium-II, and it's running the P-II L2 cache self-test routine, which, of course, fails. Thankfully, the Celeron-II processor does not disable the L2 cache when this occurs. The Celeron-I (PPGA) doesn't get buy so easily, however - the L2 winds up disabled, and has to be re-enabled using our CPU Control Panel utility (which can be done automatically) once Windows boots.
So pressing Escape every time you reboot may be a bit of an annoyance. However, it apparently can be made to work.