Dell Dimension XPS T Processor Upgrade Information
compiled by Robert Hancock
Some pictures showing an upgrade to a 1 GHz processor on a T-series machine, step by step, are available here.
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 A09 and want to upgrade the processor, I recommend you upgrade to the latest BIOS version, currently A11. BIOS versions before A09 cannot display the speed of 850 MHz CPUs properly, and versions before A06 do not include Coppermine processor support. Note that when upgrading from a version before A09 to A09 or later, the BIOS settings will be reset to defaults, so you may want to record the settings before the upgrade so you can change them back later (though the default settings will probably work just fine anyway).
These systems seem to use a Dell OEM version of the Intel SE440BX-2 motherboard, although some sources (like SisSoft Sandra) report that it has a SE440BX-3, which is an OEM-only Intel board. The SE440BX-2 board definitely officially supports non-Coppermine (i.e. Katmai) Pentium IIIs up to 600 MHz. According to Intel, only boards with certain AA (Altered Assembly) numbers support Coppermine processors. The AA numbers for standard Intel SE440BX-2 boards (which these are not) that can supposedly support a Coppermine are 719944-214 or later, 754552-200 or later, and 754558-200 or later (the "or later" referring to the last 3 numbers in the AA number being higher than those given). The AA number is located on a sticker on the motherboard, probably white with a Dell logo on it. However, these numbers refer to Intel-branded boards. Dell boards will almost certainly use entirely different AA numbers, so if your board has an AA number not in these ranges, don't panic.
So far, there have been reported upgrades using both the SECC2 and FC-PGA Pentium IIIs using a slocket.
1.1 GHz processors with a 100 MHz bus should work on these machines. So far, I have one report that an attempted upgrade with one of these on a T-series machine using an Iwill Slocket II ver. 1.2 failed, and one that a similar attempt succeeded. These are all FC-PGA processors, so you would need a slocket adapter to use one. An FC-PGA version of the 1 GHz processor with 100 MHz bus is also being released. As well, there are now 100 MHz bus Celerons up to 1.1 GHz available. These should all theoretically work as well.
These systems can also use the Powerleap PL-iP3/T CPU adapter, which allows the use of Tualatin-core Celeron CPUs at 1.2 GHz and up. Tualatin-core Pentium IIIs cannot be used as these are all 133 MHz bus only. See the review of this adapter linked to on the main page for more information.
There is a cosmetic issue on these machines and 1 GHz (and presumably higher) CPUs where the system model will be displayed as "T@00" on the boot-up screen. Apparently the BIOS code didn't take into account the effect 4-digit CPU speeds would have here. This is just a cosmetic problem, it doesn't hurt anything.
Like the R-series, these machines do not support 133 MHz FSB processors. You must use a CPU with either a 100 or 66 MHz FSB speed. See the main page for info on what processor you need.
(Note: The SECC2 1 GHz processor with 100 MHz bus has a big warning label saying it's only been tested on certain Intel server boards. This doesn't mean it won't work on others, and many people have put these in with no problems.)
The main difference between the SE440BX-2 board and the SE440BX used on the R-series is that the BX-2 has an improved voltage regulator. One XPS T owner stated their machine has a Semtech SC1185ACSW regulator controller chip. This is basically an improved version of the R-series' SC1182 regulator, with an extra voltage reference output and tighter voltage regulation. The output voltage capability remains the same.
Reportedly, these machines use a pair of 50N03-07 regulator transistors, which apparently suggests maximum ratings of 50 amps and 30 volts, and a channel resistance of 7 milliohms. If that's true, these should be capable of handling the power requirements of any processor currently out.
These machines use a plastic shroud to duct air from the case fan over the processor's heatsink to cool it. If you upgrade the processor, I would remove this shroud, it won't be compatible with other heatsinks and shouldn't be necessary either as the new heatsink should have a fan of its own.
For info on removing the heatsink/fan from a Pentium III processor, click here.
Apparently these machines (at least, some of them) use the older-style SECC CPU retention clips, which means that newer SECC2 CPUs won't be locked down by the clips. This could mean that if you use the old clips, there might be a risk of the CPU loosening up or falling out of the slot. For more information on this issue, see the section "What about using a regular Slot 1 (SECC2) processor instead of a socketed one?" on the R-series page.
As for slockets, the Iwill Slocket II is reported to work, but I have no specific knowledge about whether any other slockets work. I would read the slocket section of the XPS R page and generally stick to those recommended there.
Apparently these systems use a Cypress W149 chip as the clock generator. This chip is software addressable, and can be used to select higher FSB speeds of 103 MHz and 124 MHz, which would overclock a normally 100 MHz FSB CPU by 3% and 24% respectively. (This would, however, overclock the PCI and AGP buses slightly, as well as the RAM, which could cause problems. Some systems may not be able to handle 124 MHz.) The SoftFSB utility by H. Oda may support these machines, you have to select IC-Works W149x as the clock generator (one person found SoftFSB didn't always operate reliably though). The download for SoftFSB is no longer on that site, so if you want it you'll have to check somewhere else (one place is here). There is another program called CPUCool that has FSB-changing capability and supports this chip, and overclocking has also successfully been done on an XPS T using this program. You have to select Cypress as the PLL manufacturer and W149 as the PLL type.