P4 800 FSB step down to 533/400 FSB?

[Jeff68005]

I have an outdated (new condition) Motherboard that I never built. It is a Gigabyte GA-8PE667 Ultra that I plan to update the bios to F3 which supports Hyper Threading. I know it will handle P4 FSB 400 and 533. I have the board and memory for it. All I need is the CPU. I have my video card too. It will do the job I want when I get it up and running.

I have not done any hyperthreading, so I don't know if that affects what I am asking. All my previous CPUs were before HT was available. I was hoping to try HT with the new build.

My question is:
Can I take a P4 FSB 800 HT and operate it at FSB 533? I remember some people took P4 533 and operated them at 400. I was thinking therefore that I should be able to take a P4 800 HT (socket 478) and run it at 533 or 400. Does the HT enabled in the motherboard affect my question?

I found a new P4 2.8 800 HT is why I am asking.

I was also looking at a P4 3.06 HT.

Thanks for all replys and your patience.

 

[GhislainG]

While it might work, it will run much slower than it should. I recommend that you buy a CPU on the supported list (they are quite cheap on eBay). HT doesn't provide much benefits, if any.

 

[ulysses35]

HT / Hyperthreading doesnt effect the FSB that your CPU and Motherobard run at. Ht just tricks to OS into thinking there is two cores on your CPU (will show in Performance tab as 2 x CPU's)

I think you will have problems running a CPU with a bus speed of 800mhz on a slower motherboard.


see following link for the cpu support list


http://www.gigabyte.com.tw/Support/Motherboard/CPUSupport_Model.aspx?ProductID=1607

 

[MRFS]

This situation occurs quite often when a BIOS
pre-dates the vintage of the CPU:

If the BIOS does not recognize the installed CPU,
the machine will probably not POST e.g. no video.

For example, a larger L2 cache may not be supported
by an older BIOS version, but a newer BIOS version
may have been enhanced to support the larger L2 cache.


As the latter message recommended so correctly,
you should always start with the CPU Compatibility
List for that motherboard and its current BIOS version.

We just experienced this go-around at my office, when a
friend wanted to mix older P4s with spare motherboards
that he wanted to refurbish:

both aging Intel 550 and 631 CPUs failed in an ASUS P5GD1
-AND- in a brand new Intel DG43NB -- no video,
even though the LEDs on our Corsair XMS were
flickering normally when installed in the P5GD1,
indicating memory tests passed OK during POST.

BUT ...
... both of those CPUs worked AOK in an ASRock 4CoreDual-SATA2
motherboard that we picked up used for $35.00:

http://www.newegg.com/Product/Product.aspx?Item=N82E16813157115


AND ...
... both CPUs are also listed in the CPU Compatibility List
for a brand new ASUS P5Q-EM with Intel Q45 chipset:

http://www.newegg.com/Product/Product.aspx?Item=N82E16813131336


So, a faster CPU can still run at a slower FSB.

The BIGGER issue is whether the existing BIOS will
recognize the installed CPU.


MRFS

 

[GhislainG]

MRFS, we are talking about very different technologies here. Socket 478 and LGA 775 motherboards have nothing in common.

If the OP installs a CPU having a FSB of 800 MHz on his 400/533 MHz FSB motherboard, the CPU will run at 67% of it's rated speed. That obviously wasn't an issue that you faced with the ASRock motherboard since it supports CPUs having a FSB of up to 1066 MHz and the 631 has an 800 MHz FSB.

 

[MRFS]

No. I understand what you are saying, but we are not
talking different technologies.

If his motherboard only supports 533 and 400 MHz FSBs,
but his CPU uses an 800 MHz FSB, those facts imply to me
that his CPU was manufactured much later than that
motherboard. I confirmed this by looking at photos
and it has 6 x PCI slots.

Accordingly, there's a very real chance that the BIOS
currently installed on that motherboard will NOT
recognize the newer CPU.

I've had this very same thing happen to me
several times, when trying to mix newer CPUs
with older motherboards.

One time, we had to purchase a cheap Celeron
just to be able to flash the latest BIOS,
which was needed for an E8400 to run in
an otherwise modern motherboard.

So, there are two issues in this thread:

(1) will the newer CPU even work and, if so,

(2) what performance penalty will it suffer
if it does work at all.

In my experience, those are two very different problems
that have occurred with both PGA-478 and LGA-775 sockets.


MRFS