Hello rwbrehm,

The XPS 420 is built on the Dell BTX motherboard.  Your CPU is based upon the MOBO  and its socket.  The 420 has a 775 socket, which is what the Intel Core 2 duo and Core 2 quads fit, the 775 socket.  The 420 MOBO will handle only the 65 nm CPU's, so when you look around look at for a 775 socket 65 nm CPU.

In my two XPS 420's I am running the Core 2 Quad Q6600 which handles very nicely. 

Here is the list of compatable CPUs for your rig:

Installing the processor
The Dell heatsink will work fine. Clean the old thermal paste off with alcohol, pick up some Arctic Silver 5 thermal paste, and apply it to the processor after you install it per the Arctic Silver instructions. Be very careful of the socket when you remove the old processor and install the new one. It is extremely easy to bend one of the tiny little pins, all 775 of them. If you bend one, you likely will not be able to straighten it, and you will need to replace your motherboard. Make sure you update the bios to the latest version BEFORE you switch the processor.
HU587 Conroe Kit, E4300, 1.80G, 2MB, 800FSB, L2
DX483 Conroe Kit, E4400, 2.00G, 2MB, 800FSB, L2
DX485 Conroe Kit, E6320, 1.86G, 4MB, 1066FSB, B2
DX484 Conroe Kit, E6420, 2.13G, 4MB, 1066FSB, B2
MP160 Conroe Kit, E6550, 2.33G, 4MB, 1333FSB
MP162 Conroe Kit, E6750, 2.66G, 4MB, 1333FSB, G0
MP628 Conroe Kit, E6850, 3.00G, 4MB, 1333FSB, G0
WM543 Conroe XE Kit, X6800, 2.93G, 4MB, 1066FSB, B2
MP626 Kentsfield Quad Core Kit, Q6600, 2.40G, 8MB, 1066FSB, G0
MP627 Kentsfield Quad Core Kit, Q6700, 2.66G, 8MB, 1066FSB, G0
UP673 Kentsfield Quad Core Kit, QX6700, 2.66G, 8MB, 1066FSB, B3
RX656 Kentsfield Quad Core Kit, QX6800, 2.93G, 8MB, 1066FSB, G0
PW016 Kentsfield Quad Core Kit, QX6850, 3.00G, 8MB, 1333FSB, G0
C863D Yorkfield Quad Core Kit, QX9300, 2.5G, 6MB, 1333FSB, M1
C864D Yorkfield Quad Core Kit, Q9450, 2.66G, 12MB, 1333FSB, C1
C865D Yorkfield Quad Core Kit, Q9550, 2.83G, 12MB, 1333FSB, C1
C299C Yorkfield Quad Core Kit, QX9650, 3.0G, 12MB, 1333FSB, C0
H786G Yorkfield Quad Core kit, QX9650, 3.0G, 12MB, 1333FSB, C1
X198G Wolfdale Dual Core kit, E7200, 2.53, 3MB, FD, 65W,M0
Y932C Wolfdale Dual Core Kit, E8200, 2.66G, 6MB, 1333FSB, 65W, C0
K905F Wolfdale Dual Core Kit, E8300, 2.83G, 6MB, 1333FSB, 65W, C0
Y935C Wolfdale Dual Core Kit, E8400, 3.0G, 6MB, 1333FSB, 65W, C0
Y934C Wolfdale Dual Core Kit, E8500, 3.16G, 6MB, 1333FSB, 65W, C0
 

Other information can be found here:

http://en.community.dell.com/forums/t/19242670.aspx

Best,

Darrell WV

Wow thanks a bunch for the info this will allow me to look for a nice discounted cpu upgrade.

Still wondering about the hard drives though.. I can't imagine why the machine would have issues with 1 to 1.5tb drives in raid but want to make 100% sure it won't before i buy the drives.  Also could someone confirm the sata is sata-300 not the sata-150 please

Thanks a bunch

As it turns out i did some reaserch on my xps 420 and it looks like mine according to Windows and even the dell diagnostics is using the Q9300 processor which is based on the 45nm process. This leads me to beilieve any of the 45nm cpu's should work.

I guess Dell used a bunch of different cpu's for the XPS 420 line of machines

WOW, that is great to hear!  Remember that in addition to the MOBO, the BIOS must support the CPU, but I am with you in your line of thinking that at least some if not all of the 45nm CPU's should work, just a trial and see what happens.

Best,

Darrell WV

Just wondering if you folks had a chance to try the 45nm processors in the XPS 420 and if they worked ok?

Thanks,

-Jeff

I have just read The 420 MOBO will handle only the 65 nm CPU's and the E6600 is a 45nm, will this mean that i cant upgrade to E6600

roduct Name: INTEL PENTIUM E6600 775 RETAIL

Web Address: www.intel.com

Model Number: BX80571E6600

Package Type: Retail

Warranty: 3 Years Direct With Manufacturer

Interface: Socket 775

Bus Speed: 1066MHz

Core Frequency: 3.06GHz

Core Voltage: 0.85–1.3625V

Process Technology: 45nm

Thermal Design Power: 65W

Bus/Core Ratio: 11

L1 Cache: 2 x 32 KB instruction caches‚2 x 32 KB data caches

L2 Cache: 2MB

Hi malctan,

Please stick to one thread. Thanks.