Help w/ CPU upgrade

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I've got a Dell Dimension PC and I was thinking about upgrading the

Currently, it's got a Pentium 4, 2 GHz processor.  It's 478 pin, I
believe, and I thought it had 533 FSB, but Sandra is telling me it's
400 FSB.  How important is it to match that?  I didn't even know there
400 Mhz FSB processors.

I already have upgraded my RAM (1 GB) and graphics card (Nvidia 6800,
256 VRAM), and PSU of course.

I heard that I could upgrade my processor up to 3.2 Ghz, which I would
imagine would make a significant difference.

Any recommendations on processors or where to get 'em, and how do I
find out exactly what my FSB is if I have to match it?


Re: Help w/ CPU upgrade

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Well, let's try an example. You buy a 3.2GHz/FSB800 processor
and plug it into a FSB400 only motheboard. The processor ends
up running at 1.6GHz instead of its rated speed. The multiplier
is locked in the processor and normally would run at 200x16=3200
and if your motherboard only did FSB400, this would be 100x16=1600.
The FSB, in other words, provides the clock signal for the
CPU core, and using the wrong FSB means the core runs slower.

The other bit of bad news, is there are different families of
processors. Northwood is 0.13u. Prescott is 90nm and probably
more available than a Northwood. (Meaning a lot of "bargains"
simply won't work in your board.) It could be that your
motherboard would only accept a Northwood, and if you bought a
Prescott S478 3.2GHz/FSB800/1MB L2 cache processor, it would
not even POST in the motherboard.

That is why identifying the motherboard and looking up the
compatibility list for it, is so important. Even knowing what
the chipset is on the motherboard, could give some hint as to
what it supports. Or, in a pinch, extracting the microcode
module (something like CPUCode.exe) from the motherboard BIOS
might give a ballpark answer as to what it supports.

Based on the info you've given so far, I would think a
2.8GHz/FSB400/512KB cache Northwood would be the fastest
processor absolutely guaranteed to run. If you offered us no
other details about the board, such as the chipset, I would
think that would work. That is the one in the upper left
hand corner of this web page, for $219.95. Finding these
on some other web site is less likely (Powerleap stockpiled
these years ago.)

Some chipsets and their FSB choices are here:

and here (value desktop):

and here (performance mainstream):

You can get a utility here that will give you some info
about your chipset and motherboard peripheral chips. Or you
could try posting more details about your machine, such as
the model number, and maybe we can figure it out from that.
In any case, your shopping experience for this, is not
going to be exactly trouble free, until you get some more
compatibility info. So far, only the 2.8GHz/FSB400/512KB
looks like a safe bet.

"EVEREST Free Edition 2.20"

Another option is to read the motherboard name off the
surface of the motherboard. It should be in large white
letters, like "P4B" or "P4PE".

I'd suggest looking on the Dell site, but my success rate
there is pretty poor. That is why I'm not depending on Dell
to give us an answer.


Re: Help w/ CPU upgrade

Paul wrote:
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Wow, thanks Paul for the extremely detailed and knowledgeable response.
 I'll try out that EVEREST utility to get more information on my
motherboard.  I've searched through the DELL forums, but they weren't
helpful and I found their tech support people to be very obtuse about
upgrading processors (unsupported, i.e., they'd rather I buy a new
computer from them).

I'm thinking that if your first estimation was correct (based on the
prior information I provided), an 800MHz increase, while noticeable,
may not be worth $200+.

Again, I'll provide more details in a bit--thanks, again!

Re: Help w/ CPU upgrade

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Here is some detail on my processor:

Number of CPUs            1
APIC ID                0
Name                Intel Pentium 4
Code name            Northwood
Specification            Intel(R) Pentium(R) 4 CPU 2.00GHz
Family/Model/Stepping        F24
Extended Family/Model        0/0
Brand ID            9
Package                mPGA-478 (2h)
Core Stepping            B0
Technology            0.13um
Instructions Sets        MMX, SSE, SSE2
Clock Speed            1999.8 MHz
Clock multiplier        x20.0
Front Side Bus Frequency    100.0 MHz
Bus Speed            400.0 MHz
Stock frequency            2000 MHz
L1 Data Cache            8 KBytes, 4-way set associative, 64 Bytes line size
L1 Trace Cache            12 Kuops, 8-way set associative
L2 Cache            512 KBytes, 8-way set associative, 64 Bytes line size
L2 Speed            1999.8 MHz (Full)
L2 Location            On Chip
L2 Data Prefetch Logic        yes
L2 Bus Width            256 bits

And my chipset:

Northbridge        Intel i845PE rev. A1
Southbridge        Intel 82801DB (ICH4) rev. 01
Graphic Interface    AGP
AGP Revision        3.0
AGP Transfer Rate    4x
AGP SBA            supported, enabled
Memory Type        DDR
Memory Size        1024 MBytes
Memory Frequency    133.3 MHz (3:4)
CAS#            2.5
RAS# to CAS#        3
RAS# Precharge        3
Cycle Time (tRAS)    6
DRAM Idle Timer        16

Sorry if that went overboard.  So it does seem that I have a 400 FSB,
which I wonder would mean that upgrading the processor speed would have
minimal appreciable speed increase, at least as far as I could tell for
processes, games, etc....

Re: Help w/ CPU upgrade

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On this page, it lists FSB400 and FSB533 as supported by the chipset.
The clock generator on the board determines the choices of CPU clocks
available, so a designer could limit the board to just one speed,
but that isn't a likely way for them to do it.

The chipset is old enough that you should be looking for a Northwood
0.13u processor as an upgrade. The fastest I can think of right off
hand, is 3.06GHz/FSB533/512KB L2 cache processor in 0.13 micron
geometry. This is an example for $175. (Note - be careful when
buying these, because there are also Xeon processors at 3.06GHz,
and I've seen Pentium 4, the one you want, and Xeon processors
advertised on the same page. Your motherboard socket is socket 478
and takes Pentium 4 Northwood family processors. No 90nm processors
should work, so no Prescotts or Celeron D.)

The above example is "OEM" and comes with no heatsink. But since
your Dell likely has a custom cooling assembly, the Intel heatsink
that comes with a retail processor would likely be a waste anyway.

In terms of performance, you'd be going from 2GHz to 3.06Ghz, which
is a 50% improvement. I can play the BF2 demo on my 2.8GHz P4, so
the extra speed will help a bit.

Other system improvements would be video card and power supply.
Some game installers set requirements for DirectX hardware support,
and sometimes the video card needs an upgrade, just so the installer
will work.

If you increase the performance of the video card and processor,
that can mean the power supply load increases. (There are some
new video cards, where the power consumption actually dropped a
bit, so newer doesn't always have to mean higher power consumption.
It does mean, if you plan on doing significant upgrades to a system,
you should compare the power requirements for the old hardware,
to the new hardware, to see whether the extra loading might be
too much.)

This is data for your old processor. It uses 52.4W in terms
of the thermal design power.

This is data for a 3.06GHz Northwood. It uses 81.8W for TDP.
It could use slightly less power, if Hyperthreading is disabled.
(Your BIOS may or may not show a setting for this, if and when
the 3.06GHz processor is installed into the motherboard.)

With any upgrade, you have to compare the cost of the upgrade,
to starting again with another platform. Your current machine
uses AGP video cards, and while you can still buy some good
cards, AGP cards won't be available forever. And 3.06GHz
is as fast as it is likely to go.

Your BIOS also plays a part in the upgrade. While I don't
expect a problem plugging in the 3.06GHz processor, there
have been problems in the past with the BIOS recognizing
a processor upgrade. With Asus motherboards, they provide
a web page that lists the exact processors supported. For
some processors, upgrading to a later BIOS version is necessary
to get the processor recognized and to provide any microcode
patch from Intel. With Dell, they don't have an incentive to
continue improving the BIOS, in terms of the processors it
supports. Unless Dell provides an upgrade list of processors
known to work, there is still a slight chance the motherboard
might not POST properly with the new processor in place. And I
have no surefire tricks to give you a guarantee. Examining
the microcode patch in the BIOS file (to see if 0F29 hex family
code is supported) is encouraging, but ultimately, testing that
the processor works in the actual board, is the only way to
know for sure.


Re: Help w/ CPU upgrade

Paul wrote:
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Thanks again Paul.  As I might have mentioned before, I did speak with
Dell but they were very evasive with me about upgrading my CPU, but the
3.06 number you mention does strike me as the one they mentioned as the
max supported.  I think $175 is a reasonable price for a 50% increase
in processor speed.  I already have the power up to par (my Antec PSU
is 450).

My main concerns are a) My default cooling system is just fans, do you
think I should purchase that extra heatsink?  And if I do, what are the
chances that it will not "fit" on my motherboard (i.e., if it needs to
click in place or be screwed on, there is no place to do this)?

b) The BIOS as you warned...does the BIOS usually recognize new CPUs
automatically?  I'm afraid my BIOS capabilities are limited to checking
Dell's site for BIOS updates as downloadable files.  I am unclear how
to work with the BIOS myself.

c) You mentioned potentially turning off HT technology through the BIOS
to save on power.  Was this just a general comment, because my
understanding was that the processor you pointed out did not have HT
capabilities, and I'm worried because I'm unfamiliar with how to go
about turning off such a function (this relates back to "b", regarding
my unfamiliarity with BIOSs).

Thanks a million!

Re: Help w/ CPU upgrade

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It sounds like you are well covered for power.

Your Dell may have had a plastic cowling, CPU fan, and CPU heatsink.
That should cover processors over a reasonable power range.
But again, I don't know of a simple way to just look at a
Dell custom assembly and say it is good enough to cool an
82W processor.

It would help a lot, if the motherboard has the ability to
measure the CPU temperature. You could fit the Dell cooler
onto the new CPU, start the machine, enter the BIOS and
read the CPU temperature in a BIOS screen. Or, if you managed
to get SpeedFan, MBM5, or some other temperature readout
program to work, you could boot into Windows and see how
warm it gets. Intel processors have overheat protection,
and the computer would shut off if the processor is getting
that hot.

If the temperature is up around 60-65C while sitting idle in
the Windows desktop, then you may have to consider purchasing
an after-market CPU cooler. With the Dell, the custom cooler
or other mechanical design details may enter the picture. I
spend a considerable time researching coolers before I buy one,
to make sure they fit. With the Dell, I don't know if there
is anything in there that would get in the way of a Zalman
7000 series or some other S478 cooler.

Some after-market coolers use their own mounting hardware.
Others will use the plastic retention assembly already on
the motherboard, to hold them in place. The motherboard end
of things is pretty standard, as Intel helps define dimensions
and clearance areas for cooling. There is no simple answer to
this question, as there are hundreds of cooling solutions out

For BIOS processor recognition, the problem gets worse, the more
modern your hardware is. I would say the odds of getting the
3.06GHz to work are pretty good. To give you some idea, this
motherboard is from the same era as your Dell motherboard.
The 3.06Ghz processor needs BIOS 1001, but it needed a particular
motherboard revision (1.02), presumably to get proper
Hyperthreading support. Notice that in this case, the
Celeron processors needed a lot more BIOS upgrades to
cover their introduction.

The FSB800 entries in that table are a special case of
overclocking. A Dell motherboard is not likely to give
you the option to change the CPU clock, so buying a FSB800
processor would not be a useful option. The P4PE motherboard
could run a FSB800 processor, with one and only one DDR400
memory module, and that is an overclocking configuration.
The chipset is guaranteed to run a FSB533 processor, but
for some people, they could only reach FSB798 on the P4PE
when trying the FSB800 processor experiment.

There is an example of a BIOS setup screen here. The
"HyperThreading Technology" item might only appear if
the 3.06GHz processor is installed. The BIOS has no reason
to display that option, when any other FSB400 or FSB533
processor is installed. For the FSB533 processors, only
the 3.06GHz processor offered HyperThreading.

As a backup plan, you could also pick up another S478 motherboard,
like something with an Intel 865PE or 875P chipset. If your
3.06Ghz processor doesn't happen to POST, you could always use
another Intel chipset board to take its place. Something like a
P4P800 series board for example. Finding S478 boards at retail
is becoming difficult now, so you may have to visit Ebay to
get a good selection of boards.

Upgrading a Dell is a good test of your skills...


Re: Help w/ CPU upgrade

Paul wrote:
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Thanks once more Paul, I did put an order in for that processor.  I
know I have the power covered, but I'm a bit concerned about my PC's
temperature.  Speedfan tells me that my computer is 47 C.  I have two
fans, which are working, but for some reason aren't picked up by
Speedfan so I don't know their specific speed.

How concerned should I be about using my original heatsink w/ this new
processor?  Will I need to apply a new layer of thermal paste or is
this a no no?  From the product spec pages, it says that the thermal
guideline for the new processor is 69 C as opposed to 68 C for the
older model.  I'm unclear on what the thermal guideline referes to--the
amount of heat that my fans need to dissipate (however would I know
what they're doing?) or is that just the max temp my CPU can handle?

Many thanks again

Re: Help w/ CPU upgrade

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That would be the maximum recommended temperature. The hardware
shutdown point is much higher than that, for a 3.06GHz. Basically
you want to stay away from that temperature, because the processor
can begin to throttle back its computing effort at that point (69C).
(See "Thermal Monitor" in this doc)

Cleaning off the old thermal interface material and applying something
is a good idea. Some thermal interface materials are only
really good for one application, because they get scratched up
easily. Cleaning them off and reapplying a paste product, is
one way to do it. Basically, the idea is to avoid any air gap
between the heatsink and processor. A scratched up thermal interface
is not as good as a freshly applied one. You apply enough paste
to avoid leaving air (a thin layer), but not enough that it
gushes out - too much paste and the stuff works as an insulator.
The paste is there, only to displace the air in the air gap.


Re: Help w/ CPU upgrade

Paul wrote:
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Thanks again--do OEM CPUs generally come with some thermal paste
included?  I imagine a Radio Shack, etc. might carry paste if it's not


Re: Help w/ CPU upgrade

SirGrotius wrote:
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In case you were following this, I finally installed that CPU you
recommended (which I checked w/ Dell and finally got out of them that
that was the best I could do w/ my board, etc.), and it's working like
a breeze.  So I went from 2 Ghz, 400 FSB to 3.06 533 FSB, and I'm
surprised by how many people say upgrading one's CPU doesn't make a
noticeable difference--I noticed everything immediately!  It's like
night and just to reinstall Windows even though Dell didn't
provide me with a true Windows XP cd...

Thanks again!


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