SC420 and Cedar Mill

| | Comments (25) | TrackBacks (0)

Can a Dell® PowerEdge® SC420 be upgraded with Cedar Mill Pentium® 4 processors?

Until Steve Ketchem sent me a screenshot showing a '631 running in a SC420 (I blurred details that named the machine, etc., or that I thought might otherwise leak information), it seemed very, very unlikely indeed: there is only one report online of a SC420 being upgraded with a '631 and the preponderance of evidence suggested otherwise. It appeared that the Intel® E7221 northbridge used in the SC420 simply doesn't support the Cedar Mill processors, making BIOS support a moot point, but Steve's email complicates the picture.

Why Would I Want To?

Simply: value for money and not needing a heatsink/fan assembly the size of Texas.

The LGA775-packaged Intel Pentium 4 family can be divided into those with the 65nm Cedar Mill core, which include all of the 6x1 (e.g. 631, 641, 651, and 661) sequence; those with 90nm Prescott core, including the 5xx sequence (e.g. 521, 522, 524, 531, 541, and 551); and those with the 90nm Prescott 2M core, which includes all of 6x0 sequence (e.g. 630, 640, 650, 660, and 670). The ancient Williamette and Northwood cores predate LGA775 and Intel's current 3-digit numbering scheme.

The problem is that the 90nm Prescott cores gobbled power and, infamously, ran as hot as the hob of hell. They were sold at a time when Intel were having their asses handed to them by AMD™ and the only thing Intel could do, in advance of releasing the 65nm dual-core processors, was ramp up the clock-speed on their aging NetBurst™ processor architecture and put giant cooling assemblies on top. The TDP (thermal design power) of Prescott cores is 115W compared to 86W for a comparable Cedar Mill core, representing at least one third more energy having to be dissipated as heat. If you think 29W doesn't sound like much, try gripping a 25W lightbulb.

Now that both Prescott cores are obsolete, the Cedar Mill processors are, cycle for cycle and cache for cache, much better value for money, use less energy, and need less cooling. Only a fool would use either Prescott when he could use Cedar Mill.

The Case

The Charges

The Dell PowerEdge SC420 stands accused of failure to support Cedar Mill processors.

Stipulated Facts

The SC420 uses the Intel E7221 northbridge, according to the published specifications (PDF). This is confirmed by CPU-Z which reports a chip ID of 2588 consistent with the E7221.

Both the Intel E7221 northbridge, and the Dell SC420 which uses it, were developed long before the advent of the 65nm Cedar Mill core. The E7221 definitely supports the Prescott and Prescott 2M 90nm cores, since they are listed on Intel's Supported Processors page for their SE7221BK1 server platform, which uses the E7221 northbridge.

Case for the Prosecution

The list of supported processors for the Intel SE7221BK1-E motherboard does not include any 65nm/6x1 series processors.

The online product information for the SuperMicro P8SC8 and its siblings, the P8SCi and P8SCT motherboards, also based on the same chipset, explicitly state: “Supports an Intel® Pentium® 4 processor 6x0 or 5x0 sequence on 90nm process ONLY...” (their capitals).

Although the PowerEdge forums contain conflicting and confusing suggestions and opinions, there is not one single report of a working 6x1 processor. On the contrary there are at least two posts which report failure: this post and this one in which the poster also says that multiple similar failures are reported on a Japanese SC420 site.

Case for the Defence

Dell says that you can upgrade the processor in the SC420 and stipulates the processor requirements as “Intel® Pentium® 4 processor with a minimum clock speed of at least 2.8 GHz, and front-side bus speed of at least 800 MHz and at least 1 MB of internal cache”. The Cedar Mill processors meet these requirements.

Dell released BIOS Update A02 for the SC420 on the 13th of February 2006, which “Added support for newer CPUs”, this was after the release of the Cedar Mill Pentium 4 on the 3rd of January.

The customer reviews of the 631 processor on include one which states “Workes great in my Dell Poweredge sc420”.

The Prosecution Responds

The quotes from the Dell literature are accurate and were correct when it was written. They did not anticipate Intel developing and marketing a processor as a “Pentium 4” when it was not compatible with the E7221. How could they? You cannot expect that either Dell or Intel would plaster this incompatibility all over the place: their silence is deafening.

Yes, Dell did indeed produce that BIOS update and it was, indeed, after the release of Cedar Mill. However, it was also after the release of the Prescott 2M cores which are supported. They say “added support for newer CPUs”, not “added support for all of the latest 65nm CPUs”, now that would be convincing!

Now, let's examine that customer review again. It says “Workes (sic) great in my Dell Poweredge (sic) sc420 (sic)”. Could someone who made all those spelling and capitalisation errors not have typed 420 where he meant 430 ? Or, perhaps, posted a review to the 631 thread when he actually bought a 630, just going on the speed and other parts of the description?

The Verdict

In light of Steve's email, I might try a SL9KG Cedar Mill processor (Steve's screenshot shows a 631 with D0 stepping, which can only be the SL9KG) in one of my four SC420s, but it's still pretty clear that you can't sling in any Cedar Mill processor and expect it to work.

The best “definitely” SC420 compatible processor, as far as I can tell, is one from the a 6x0 sequence. The 6x0s have two advantages over the 5xx sequences: having the “enhanced Intel SpeedStep technology”, so the processor can be clocked down when under lighter load; and having 2MiB of L2 cache.

Share Your Experience

If you have used a Cedar Mill processor in an SC420 or any other board with the E7221 northbridge, please comment below.

0 TrackBacks

Listed below are links to blogs that reference this entry: SC420 and Cedar Mill.

TrackBack URL for this entry:


Since I updated this with news from Steve Ketchem, but before I moved it over to Movable Type, Peter N also confirmed a 631 working in an SC420, again with stepping D0, suggesting an SL9KG.

Thanks for all the information you've put together here. It's been very helpful for me.

I have two SC420s that came with low end 2.53GHz Celeron D processors. I've successfully upgraded one of them with a SL9KG I bought used online.

I verified with Intel's Processor Identification Utility ( as well as CPU-Z. I have detailed screenshots, pictures of the SL9KG itself, and report files if you'd like me to email them to you.


Hi Brent,

Thanks for that information and more evidence of the SL9KG working in a SC420. By all means, mail me the details, and I'll keep a copy in case any new evidence comes to light. I'm particularly thinking that if, in the future, I got a report of an SL9KG not working, then it would be useful to have the details of your working setup to see the differences.


I'm running a 650 Prescott.
Surprised the 6X1 actually works.


Me too, but it seems like it's only the SL9KG variant. Other 6x1's were widely reported not to work.



I have one of the above mentioned SuperMicro p8SCI machines, which I acquired so cheaply that I felt enboldend to try the unsupported upgrade to a Cedar Mill processor, (SuperMicro's capitals not withstanding).

To my unworthy delight, is works...seemingly perfectly. Only time will tell if there are any ill affects.

I used a 3.2 641 sl9kf chip, it was just languishing in a decommissioned desktop, so I thought WTF?




The SL7PR is compatible, the SL8CP isn't. They're both 90nm processors, except the the SL8CP is an 820. Shame it doesn't seem to work. Thought it was worth a try, but don't bother.

I just won an SL9KG Cedar Mill and installed it in my Dell SC420. Works like a charm! Just remember to flash your Bios to A02 before you pull the old one out...

The annoying thing is that the CPU retainer bracket is not standard so I couldn't put a new Zalman fan on it like I had planned. So it's running with the stock passive heat sync for now.

Any thoughts of a good CPU fan?


Any thoughts of a good CPU fan?

Well, given that the TDP of the Cedar Mills is less than the Prescotts that SC420 is designed for, the Dell cooling arrangement (for want of a better description) should be more than adequate.

I upgraded my SC420 based upon the comments in here. Everything worked without a single problem
Old System
1GB Ram, 2.8GHz cpu, 2 80Gig Sata Maxtors running under Cerc 2S Raid (1 hdd bad), and CDRom. Running Windows Server 2003
New System
4GB Ram, 3.2GHz 641 sl9kf, 1TB Seagate, Barracuda with working 80GB Maxtor (was able to recover old data. Running as non-raided Sata drives, and a new LG DVD reader\writer. Installed Windows Server 2008 x64 SP2.


I was just wondering if a SL729 cpu will work with A02? It appears that it will because it is a 630 series... Anyone have an idea?



Based on info gathered here and elsewhere, I just changed the SL7PR that came with my SC420 for an SL9KE. I had already changed Bios to A02. Works flawlessly. Win 7 detected and changed driver for CPU. CPUid shows processor core speed fluctuating between 2.4 and 3.4ghz depending on load. Much better performance overall.

Anyone succeeds with Intel Core Duo and Dell SC420.

It sounds the best you can do is SL9KE so far.

I upgrade the original 2.8GHz to SL9KE. It works flawlessly as well. Not sure if it works with any Core Duo or Core 2 though.

It sounds at least one Pentium D works in Dell SC420.

Here is an example.

It seems someone was selling Mail Server (DELL PowerEdge SC420 Serer with Pentium D 2.8GMhz , ECC DDRII 1GB RAM)


Word of warning:
My Dell Poweredge SC420 did not accept the Cedar mill core (631 / SL9KG) with the A02 BIOS. No 64 bit for me now :(

Regards, Michiel.

I'm still using my sc420 as a desktop. Recently installed an Intel P4 3.8ghz 670. The machine hicupped with some errors, ?checkpoint wake and checkpoint ithr? but is now running very well and very fast.

I just made the upgrade from a 2.8GHz Prescott to an SL9KE 3.4GHz using A02 BIOS. Working great! CPU-Z shows speeds of 2.4GHZ and 3.4GHz with SpeedStep.

Just tried SL9KE with A02 BIOS and the cpu fan runs full blast and the screen remains blank without any disk activity. The power light is amber and I have to turn off the box for it to stop. I'm using the original factory heatsink. Not sure if the cpu is bad because it was bought used (I can return it). Wondering if anyone has any ideas. I'm able to put my old 2.8GHz Prescott back in and use without any issues.

Hi Emmet,

Thank you for all the research you've done regarding upgrading the processor with a faster one. It's extremely helpful!

I just wanted to report another successful upgrade. I upgraded my stock 2.8Ghz to a SL9KE 3.4Ghz (Yay! 64Bit). I'm using the A02 BIOS from Dell and have screenshots if you'd like to see the CPU-Z report (I can also email you the report).

I'm noticing a power savings of 60W to boot! Run this think long enough and it'll pay for itself, lol.

Thank you everyone for commenting and researching.

Sean Rackley

I just installed the SL9KE and am having the same behavior that Danny (sohoclius) described, in that the server does not screen remains blank, power light is amber, and no disk activity. Perhaps another case of bad CPU, but I am running A02.

Danny, were you ever able to get things working?


Many thanks for the pointers - I successfully just installed a P4 3.4GHz dual core CPU (cost £14.99 on ebay) to replace the single core 2.53GHz and it's like a new machine.

If anyone wants screenshots or anything, feel free to ping me a mail at

CPU used was an INTEL® Pentium4 3.40GHz 2M 800MHz SL9KE

All the best, B

Brian the SL9KE is a single core processor

Thanks to this article, I successfully upgraded my SC420 to a SL9KE processor and it's been running fine for 3 weeks now.

I've got a PowerEdge 800 that also uses the same E7221 chipset. Has anyone tried a (SL9KD, SL9KE, SL9KF, SL9KG) in a PE800? Does anyone have evidence that it would not work?

I have two SC420s that can take the Cedar Mill if it doesn't work in the PE800, but I'd like to get some sense of the probability that it would work.