Optiplex 745 USFF and Optiplex 755 USFF CPU upgrade problems.

[Anonymusen]

Hello everyone.

My english could be better, but I hope it goes.

My problem is that I have a Dell Optiplex 745 USFF with 2.6.6 bios and a Optiplex 755 USFF with A22 bios. So they are both bios updated.

I have heard a lot about that the Dell USFF cant run Quads processors over 65W because of the external power brick on only 220W. But i thought i will give it a try, so i did buy some cheap quads (Q6600, Q8400)

First i tried the Q8400 in my Optiplex 755 USFF, but It just keep going spin up and off, spin up and off with yellow light on the power button. Then i tried the Q6600 also in my 755. it did boot up, but says: incompatible processor ..

Then I tried the Q6600 in my 745 USFF. It boot up and run great? I have not tried the Q8400 in my 745 because I know it cant run 1333MHz processor.


But why do my 745 USFF work with Q6600 when my 755 does not?

i prefer using the 755 because of higher ram and cpu speed.

Regards

[beamermt79]

Don't know the technical explanation but from the spec sheets, it looks like the quad core processors were locked out on the 755 for whatever reason.  Regardless, those processors run at higher then 95W and if your system is only rated at 65W you run a high risk of damaging the motherboard.

[speedstep]

Quad Core wasn't locked out on the 755.  The Q6600 and Q6700 are listed as standard.  There are over 20 bios revisions however. So you need current bios and you cant jump from A01 to A22 in one step.

USFF units cannot use QUAD core because their power supply is too small.

http://www.dell.com/downloads/global/products/optix/en/opti_755_techspecs.pdf

Description

BIOS	Version	Download
Dell Optiplex 755 System BIOS This package provides the BIOS Update for Dell OptiPlex 755 running the following Operating Systems: Windows and DOS.More details	A22
DELL,DSK PROG,BIOS,OPTI-755,,A21 OptiPlex 755 System BIOSMore details
Dell OptiPlex 755 System BIOS, A19 This package provides the BIOS update for Dell Optiplex 755 running the following Operating Systems: Windows and DOS.More details	A19
Dell OptiPlex 755 System BIOS, A17 OptiPlex 755 System BIOSMore details	A17
Dell OptiPlex 755 System BIOS, A16 OptiPlex 755 System BIOSMore details	A16
Dell OptiPlex 755 System BIOS, A15 OptiPlex 755 System BIOSMore details	A15
Dell OptiPlex 755 System BIOS, A14 OptiPlex 755 System BIOSMore details	A14
Dell OptiPlex 755 System BIOS, A13 OptiPlex 755 System BIOSMore details	A13
Dell OptiPlex 755 System BIOS, A12 OptiPlex 755 System BIOSMore details	A12
Dell OptiPlex 755 System BIOS, A11 OptiPlex 755 System BIOSMore details	A11
Dell OptiPlex 755 System BIOS, A10 OptiPlex 755 System BIOSMore details	A10
Dell OptiPlex 755 System BIOS, A09 OptiPlex 755 System BIOSMore details	A09
Dell OptiPlex 755 System BIOS, A08 OptiPlex 755 System BIOSMore details	A08
Dell OptiPlex 755 System BIOS, A04 Dell OptiPlex 755 System BIOSMore details	A04
Dell OptiPlex 755 System BIOS, A03 Optiplex 755 BIOSMore details	A03
Dell OptiPlex 755 System BIOS, A01 Initial BIOS release.More details	A01

[beamermt79]

They were talking about the USFF not the SFF

[Anonymusen]

My 745 USFF runs great with Q6600 processor and 2gb PC2 6400 800MHz memory.

Idle temp is 35-45ºC and under max load the temp is 70ºC so im not concerned.

I have found out that you cant count on the technical sheets from Dell. Because it also says that 745 USFF CAN'T run Quads processor and 800MHz memory speed.

But mine 745 USFF runs great with Q6600 and PC2 800MHz memory.

The technical sheets also says that 755 DT max can run 8gb memory, but mine 755 DT runs great with 16gb.

Is there somehow i can unlock the 755 USFF, so it can run Quads like the 745 USFF can?