Dell Dimension XPS R Processor Upgrade Information

compiled by Robert Hancock


What can I gain from this upgrade?

Once your system is upgraded to a new processor, it will be about as up to date as any system using that processor at least as far as the CPU, motherboard, and memory performance are concerned. The motherboard and chipset in this system shares a great deal with the XPS T systems

I've upgraded my XPS R350 system to a Pentium III-700. I've listed some details on parts I used and some before and after benchmarks here.

I've received some benchmarks as well as details on the parts used from another upgrader who moved from the original Pentium II-400 MHz processor on his system to a Pentium III-700. Click here to view.


So, how do I go about doing this?

BIOS & Software:

For reference, the list of changes in all Dell BIOS versions for this system is available here.

You will probably want Dell BIOS version A09 or later when upgrading the CPU (actually, earlier versions may work, but I would advise upgrading because there are some possibly important fixes included in later versions anyway). I would recommend you upgrade to at least version A12, as there are a number of potentially important fixes in that version.

A note about upgrading to the A13 BIOS: Your system will probably redetect a bunch of the motherboard resources when your system boots up again after upgrading, don't be alarmed. You may have to reinstall the video and/or sound card drivers later on if they don't reinstall themselves properly. If you don't want to have to worry about this, and don't think you need any of the fixes in A13, you could try version A12, which used to be available on Dell's FTP site here but isn't anymore. You can view a directory of all available versions here, the ones for the R-series all begin with XPSR (right now only A13 is on there though). However, Bob Matthews' page does have a copy of A12 available for download.

As for the Intel BIOS that you can download from Intel's site, I'm not sure whether a Pentium III upgrade will work or not with this BIOS. I believe it does try to prevent Pentium IIIs over 450 MHz from being installed, but it may let you install a Coppermine as it may not recognize that as a Pentium III. I don't know if anybody has tried it though. (Note: You cannot install this BIOS the normal way, as the flash program detects a non-standard BIOS installed and refuses to flash. You have to remove the one jumper from the motherboard and reboot with the flash disk in the drive - there will be no video during the flash process. Some documentation on this process is available here under the BIOS Recovery heading. I don't know if it's possible to return to the Dell BIOS after flashing to the Intel version. For this reason, and because there is little benefit to using the Intel BIOS, I would not recommend trying to install the Intel BIOS.)

I've seen one report that when someone attempted to upgrade to a 450 MHz Pentium III processor (the only non-Coppermine Pentium III that this board supports) with the Dell BIOS version A13, it displayed a warning message and refused to boot. Going back to an earlier BIOS version seemed to prevent this. This doesn't seem to be an issue with Coppermine processors, however, because it doesn't seem to realize that the CPU is a Pentium III and lets you boot up.

Finally, if you have a Sound Blaster Live! sound card, you should upgrade the drivers for it to the latest available version before upgrading the processor, or you may experience system lockups and/or blue-screen errors after upgrading the CPU. Apparently old versions of 3dfx Voodoo3 video card drivers can cause problems with newer processors as well, if you have one of those cards you should get the latest drivers from 3dfx.

Parts needed - Pentium III upgrade:

The most common processor upgrade that's been done is to a newer Pentium III CPU. Only the newer Coppermine processors will work, the older Katmai processors will not (except perhaps the 450 MHz one) because they consume more power than this board's CPU voltage regulator can supply. See the main page for info on how to tell which kind a processor is.

Theoretically CPUs over 750 MHz may cause the motherboard's voltage regulator to heat up more than the fastest officially supported CPUs do. However, the difference in average power consumption is rather marginal, so I don't think this is very likely to cause a problem - and many people have put in 800 MHz to 1 GHz processors with no problems reported yet.

(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 use of the newer 1 GHz and 1.1 GHz, D0-stepping (CPUID 068A) processors in the R-series machines is more questionable. They have increased power draw and thermal design power, which may make their use in these machines risky because of potentially excessive demands on the motherboard's voltage regulator. These CPUs are only sold in FC-PGA format, not in SECC2, so there is no possibility of accidentally getting one when buying an SECC2 1 GHz processor, which have become a popular upgrade for these machines. If you did want to use one of these D0-stepping chips, you would need a slocket adapter. I do have one report of a successful 1.1 GHz upgrade on an R-series machine, no ill effects reported yet.

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.

Processors which work at 133 MHz FSB will NOT work on these machines. See the main page for info on how to know which ones these are. The fastest bus speed these machines support is 100 MHz. (Note that there are two versions of the 1 GHz, the 100 and 133 MHz bus versions - you want the 100 MHz bus version.)

You can use two types of processors with these systems. The first is FC-PGA, this is in a socket format, as opposed to the slot format (SECC) that these machines normally use. Because of this, a slot-to-socket adapter, commonly called a "slocket" is needed to install one of these processors. You can also install a regular Slot 1 CPU like the ones these machines came with originally, see the SECC2 section below for more details on this. In this case you don't need a slocket adapter.

See the main page for more detailed information on installation.

Parts needed - Celeron processor upgrade:

Except as noted, this is basically the same as the Pentium III Coppermine FC-PGA upgrade.

Both PPGA and FC-PGA Celerons should work, although most people have used FC-PGA chips.

The most conservative option with a Celeron is to set the voltage and FSB jumpers on the slocket to automatic, this will cause it (and your system) to run at a the CPU's standard FSB speed: 66 MHz for Celerons below 800 MHz, and 100 MHz for Celerons above 800 MHz..

Or, if you are more adventurous, and your Celeron normally runs with a 66 MHz bus, you can use the slocket's FSB selection jumper to force a 100 MHz FSB. This will cause the Celeron to run overclocked, at a speed 50% faster than its rated speed (i.e. a 566 will run at 850 MHz). (Of course this will void the warranty on the processor, + all the usual other disclaimers about overclocking...) To make it run at this speed, you'll likely have to increase the voltage setting on the slocket (i.e. don't use the auto setting).

The default voltage for PPGA Celerons is 2.0 volts. Most FC-PGA Celerons below 633 MHz have a default voltage of 1.50 volts, and most of 633 MHz and above have a default voltage of 1.65 volts. However, FC-PGA Celerons that are the newest C0 stepping (aka stepping 6) all have a default voltage of 1.70 volts. Your processor should have a code marked on it starting with S (the S-code). You can look up your processor's S-code in the Intel Celeron Specification Update (available here) to see what stepping it is.

For FC-PGA Celerons that normally run at 1.50 volts (the only ones I have detailed accounts of people using) you will likely have to increase the voltage to somewhere around 1.60 to 1.65 volts to make the processor run stably. I recommend starting at about 1.60 and increasing the voltage in 0.05 volt steps until the system boots up properly and runs without crashing. (Use the lowest possible voltage that allows the chip to run properly, as increasing voltage also increases heat production and possibly shortens chip life.) Some processors may not be stable running at 100 MHz FSB until the voltage is increased to 1.80 volts or more, and some may not work at 100 MHz FSB no matter how much the voltage is increased - if that happens, you will have to either run it at 66 MHz FSB speed (i.e. not overclocked) or get a different processor. There are no in-between FSB settings on this motherboard. Note that although some slockets may have a 133 MHz FSB jumper position, this motherboard does not support that speed.

What voltages Celeron CPUs with default voltages of 1.65 or 1.70 volts need to overclock to 100 MHz FSB is not known. However, you should take the higher standard voltage into account when setting an initial testing voltage for overclocking.

Obviously to overclock these processors you need a slocket that has FSB selection jumpers like the Iwill Slocket II. Some slockets don't have these, they can't be used for overclocking.

There have been a number of people who have been able to run a Celeron-566 overclocked to 850 MHz with the processor being quite stable. A few people have been able to use an older PPGA Celeron-366 and run it at 550 MHz.

It seems that sometimes the SisSoft Sandra utility incorrectly detects the FSB speed when you overclock one of these processors.

I do have concerns about how much power these processors consume when overclocked - obviously Intel's specs don't contain this data! It may or may not be too much for this board to handle safely. See the technical discussion later on for more info on this issue. However, I haven't heard any reports of anyone burning out their motherboard yet..

Whatever option you choose, be sure you have the correct heatsink/fan for your processor, some heatsinks have different versions for PPGA and FC-PGA. For running at 66 MHz FSB (no overclocking) the Intel boxed CPU heatsink/fan should be sufficient. If you are overclocking, however, you may want to use a larger heatsink/fan to ensure the processor stays cool. Again, as I mentioned on the main page you should make sure that it actually fits properly onto the slocket and properly contacts the processor core.

Once you have your CPU (and slocket, if using an FC-PGA processor): Follow the installation instructions on the main pagefor "FC-PGA processor installation on Slot 1 board using slocket adapter" for an FC-PGA processor or "Slot 1 processor installation on Slot 1 board" for an SECC2 processor.

After installing the new processor, you should be able to power on your system and enjoy your now faster machine. (Note: Apparently on BIOS version A09 you may have to enter maintenance mode setup by moving the jumper (see Dell manual for details), set the processor speed to 450 MHz, save, move the jumper back to normal and reboot for it to work, though some report that it works alright without using maintenance mode. For later BIOS versions this should not be needed.) The Dell BIOS won't identify your processor properly in the bootup screen, it will display it as a Pentium Pro 500 or something silly like that. However, the processor speed should still be correct. The Dell BIOS doesn't have the ability to turn the Pentium III's processor serial number off, to do this you can use this program from Intel.

If you encounter problems, see the troubleshooting section on the main page.


How are you able to do these upgrades with these systems? (more technical stuff)

The XPS R series systems use an OEM version of the Intel SE440BX motherboard - note this is not to be confused with the later SE440BX-2 motherboard used in the XPS T series systems. With respect to the processors this board officially supports, Intel says that the only Pentium III CPU supported is the 450 MHz version, and states:

"IntelŪ Pentium III processors that run internally faster than 450 MHz are not supported because the maximum Icc current required is greater than what can be supplied by the motherboard's on-board voltage regulator."

From Intel's Pentium III datasheet for SECC2 processors, it can be seen that the 450 MHz Pentium III draws a maximum of 14.5 amps of current (see p. 26). The 500 MHz Pentium III CPU (no E) draws 16.1 amps. Obviously the maximum current output of this board's voltage regulator (at least according to Intel) lies somewhere between these two numbers.

However, the Coppermine processors are fabricated using a 0.18 micron process, as compared to the older 0.25 micron process used in the older Katmai Pentium IIIs and the Deschutes Pentium IIs these systems are originally equipped with. This means they produce less heat, and more importantly for us, consume less power. A 500 MHz Coppermine Pentium III consumes only 10.0 amps, and a 750 MHz Coppermine processor consumes 15.0 amps, slightly over that of an older 450 MHz processor (see Intel's Pentium III datasheet for PGA370 processors for this information, on p. 24). However, once you get over 750 MHz they all start to exceed the P3-450's current draw more and more, which could cause problems.

Besides current, voltage is another consideration. The Pentium IIs and older Pentium IIIs used a CPU core voltage of 2.0 volts, while the newer Coppermine Pentium IIIs require a voltage of 1.60 or 1.65 volts.

The voltage regulator control chip on my system's motherboard is a Semtech SC1182CS, its data sheet is available on Semtech's web site here. (It's a rectangular chip below the processor slot.) This data indicates that this regulator supports output voltages ranging from 1.30 volts to 3.5 volts, including the 1.60/1.65V voltages needed by Coppermine CPUs (see p. 4). The voltage ID signals that produce these voltages also match those put out by the CPU to request these voltages according to the Intel datasheets. So it would appear that putting out the proper voltage is not a problem for this motherboard. Many other older BX motherboards don't seem to support the proper voltages for Coppermine CPUs, so I guess we can consider ourselves lucky..

The voltage regulator chip is what selects the voltage and ensures it remains at that level, but it doesn't actually do the regulating itself, it controls a power transistor which is what actually controls the power. On my board, that transistor is a Philips PHB21N06LT, its datasheet is available on Philips' web site here. (It's a square-shaped device near the control chip, it has 2 legs attached to the motherboard and one stubby leg that doesn't have anything attached to it.) The important info on this datasheet is the maximum current it can handle, it is given as 19 amps at 25 degrees Celsius and 13 amps at 100 degrees Celsius. This means that 19 amps is the theoretical absolute maximum current this board can handle.

With the info from these datasheets we can do a bit more number crunching. The following data on processor voltage and current can be obtained from Intel's datasheets for Pentium II, Pentium III SECC2, and Pentium III PGA370 processors. The processor power is calculated using the formula Power = Voltage x Current. The voltage regulator dissipation is calculated by using some of the formulas in the Semtech datasheets (except the "body diode recovery losses" part is not included). These formulas ask for a on-state resistance for the transistor, I used 0.060 ohms as given in the transistor datasheets, although this is quite a bit higher than the values given for other similar transistors in the Semtech datasheets. This doesn't really matter that much though, the relative differences between the numbers should be the same.

Processor Voltage Current
(Amps)
Processor
Power
(Watts)
Estimated
Voltage Regulator
Dissipation
(Watts)
Thermal
Design Power
(Watts)
P2-350 2.00 10.8 21.6 3.34 20.8
P2-400 2.00 12.0 24.0 4.06 23.6
P2-450 2.00 13.6 27.2 5.12 26.4
P3-450 2.00 14.5 29.0 5.77 25.3
P3-500 2.00 16.1 32.2 7.03 28.0
P3-550 2.00 17.0 34.0 7.79 30.8
P3-600 2.05 17.8 36.5 8.68 34.5
P3-500E 1.60 10.0 16.0 2.42 13.2
P3-550E 1.65 11.0 18.2 2.95 14.5
P3-600E 1.65 12.0 19.8 3.45 15.8
P3-650 1.65 13.0 21.5 4.00 17.0
P3-700 1.65 14.0 23.1 4.58 18.3
P3-750 1.65 15.0 24.8 5.21 19.5
P3-800 1.65 16.0 26.4 5.87 20.8
P3-850 1.65 16.2 26.7 6.01 22.5
P3-1000 1.70 19.4 33.0 8.65 26.1
P3-1000 D0-stepping 1.75 20.2 35.4 9.58 29.0
P3-1100 1.75 22.6 39.6 11.86 33.0

(Chart color coding for regulator power dissipation: Green: should be OK, Orange: maybe OK, Red: probably not OK)

Thermal design power in watts refers to the amount of heat the processor produces, and therefore serves as a rough indicator of the average power consumption as well. In contrast, the current figure and the derived wattage figure probably constitute peak values over a fraction of a second under the worst possible conditions, and therefore don't represent the average consumption.

You can see that even the 1 GHz processor only consumes just a hair more average power than a Pentium III-450, which is the fastest officially supported processor according to Intel. Therefore I don't think it's very likely to cause problems with the regulator. Technically the fastest CPU that stays under the maximum regulator power dissipation (for the given amp draw figures for the CPUs) of the P3-450 is 750 Mhz. However there have been quite a few people who have put in 800 MHz, 850 MHz, and 1 GHz CPUs with no problems reported yet, nor any reports of excessive heat from the voltage regulator. Therefore, I would say that going with any CPU up to 1 GHz should be relatively safe.

The use of the newer 1 GHz and 1.1 GHz, D0-stepping (CPUID 068A) processors, which are apparently coming out, in the R-series machines is more questionable. As you can see from the table above, they have increased power draw and thermal design power, which may make their use in these machines risky. These CPUs are only sold in FC-PGA format, not in SECC2, so there is no possibility of accidentally getting one when buying an SECC2 1 GHz processor, which have become a popular upgrade for these machines. If you did want to use one of these D0-stepping chips, you would need a slocket adapter.


Why can't I just overclock the original processor, or a Pentium III processor?

The only known way of doing any processor overclocking on these machines is running a Celeron processor at 100 MHz FSB as mentioned earlier. All processors made since midway through the Pentium II era (which probably includes most or all of the ones that came in these machines originally) are multiplier-locked, so the CPU will only run at the multiple of the FSB speed that it is designed and tested to run at. The only other way of overclocking a Pentium II or Pentium III would be to increase the FSB speed past 100 MHz.

However, this does not appear to be possible on this board. The clock generator chip on my system's board is a Cypress 48C101-01, its datasheets are available here. (It's a rectangular chip, mounted on the right side of the board in the area of the AGP slot, next to a small silver can which is presumably the clock crystal itself.) This data reveals that this chip's FSB setting is set based solely on the signals received from the processor slot, so it is not changeable through software, and in addition, the ONLY supported FSB speeds are 66 MHz and 100 MHz anyway.


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