Problems oveclocking FSB beyond 217 MHZ

[Greysky]

I have a bit of a problem... I have a P4P800 that I want to overclock. I am
using a 2.8Ghz p4, 800Mhz CPU. I also bought a gig of Corsair TwinX PC3200
RAM, and a ATI 9800 Pro video card. Sounds like a decent system to OC,
right? Well, I can only bring up the FSB to 217 Mhz before windoze XP begins
to crash on me, and this translates to a measly 3.09 Ghz. If I go higher,
the board doesn't boot. It is not a heat problem - I have a Zalman
CNPS7000CU heatsink (which is just a huge chunk of copper) as a heatskink,
and my CPU doesn't go beyond 36 C. I can't think what else I may try to get
better performance - I have heard of people going safely to at least 3.6
GHz.... am I doomed to remain on the floor of overclocking heaven? Any
suggestions appreciated.

 

[Ed Jay]

I have a bit of a problem... I have a P4P800 that I want to overclock. I am
using a 2.8Ghz p4, 800Mhz CPU. I also bought a gig of Corsair TwinX PC3200
RAM, and a ATI 9800 Pro video card. Sounds like a decent system to OC,
right? Well, I can only bring up the FSB to 217 Mhz before windoze XP begins
to crash on me, and this translates to a measly 3.09 Ghz. If I go higher,
the board doesn't boot. It is not a heat problem - I have a Zalman
CNPS7000CU heatsink (which is just a huge chunk of copper) as a heatskink,
and my CPU doesn't go beyond 36 C. I can't think what else I may try to get
better performance - I have heard of people going safely to at least 3.6
GHz.... am I doomed to remain on the floor of overclocking heaven? Any
suggestions appreciated.

What frequency did you say your PC3200 modules are rated for?

Ed Jay (No M to reply)

 

[Paul]

What frequency did you say your PC3200 modules are rated for?

Ed Jay (No M to reply)

That is where the memory clock selection comes in. Asus, in their wisdom,
have the BIOS memory clock setting showing the frequency that would
exist under nominal conditions. When you overclock, you need to scale
the frequency shown by the degree to which you are overclocking.

At FSB800, your nominal memory options are DDR333 and DDR400. Using
DDR333 is easier on the memory (and the actual value is a non standard
DDR320, when the indicator reads DDR333).

Your memory-limited overclock can be reached by setting the memory
to DDR333, then overclock to:

DDR400
------ x 2.8GHz = 3.5GHz
DDR320

What this means is, when you set up the FSB. such that your 2.8GHz
processor reads 3.5GHz, a setting of DDR333 (really DDR320) on the
memory gets scaled to DDR400 (the spec limit for the memory). As you
further indicated that your DDR400 memory can go to 217MHz, you might
even make it to

(434/320)*2.8 = 3.8GHz

So, even with your current memory, there is room to be heroic

For real overclocking fun, PC3500 or PC4000 memory make the job a
little easier, especially for those folks who start with a 2.4GHz
processor.

When trying these overclocks, it doesn't hurt to feel around the
board, for any components that are overheating. I was surprised to
read yesterday that the Northbridge has a power dissipation of
over 10 watts, and so you should be wary of any components that
are so hot you cannot keep a finger on them. Test with a program
like Prime95 or CPUBurn or the like, for short periods of time,
until you are satisfied that the system is cooled properly, and
stable at the new overclock. You should also, at some point, run
memtest86 from memtest86.com, to make sure the memory is really
solid - no sense fighting other problems when it is really the
memory at fault.

HTH,
Paul

 

[Greysky]

That is where the memory clock selection comes in. Asus, in their wisdom,
have the BIOS memory clock setting showing the frequency that would
exist under nominal conditions. When you overclock, you need to scale
the frequency shown by the degree to which you are overclocking.

At FSB800, your nominal memory options are DDR333 and DDR400. Using
DDR333 is easier on the memory (and the actual value is a non standard
DDR320, when the indicator reads DDR333).

Your memory-limited overclock can be reached by setting the memory
to DDR333, then overclock to:

DDR400
------ x 2.8GHz = 3.5GHz
DDR320

What this means is, when you set up the FSB. such that your 2.8GHz
processor reads 3.5GHz, a setting of DDR333 (really DDR320) on the
memory gets scaled to DDR400 (the spec limit for the memory). As you
further indicated that your DDR400 memory can go to 217MHz, you might
even make it to

(434/320)*2.8 = 3.8GHz

So, even with your current memory, there is room to be heroic

For real overclocking fun, PC3500 or PC4000 memory make the job a
little easier, especially for those folks who start with a 2.4GHz
processor.

When trying these overclocks, it doesn't hurt to feel around the
board, for any components that are overheating. I was surprised to
read yesterday that the Northbridge has a power dissipation of
over 10 watts, and so you should be wary of any components that
are so hot you cannot keep a finger on them. Test with a program
like Prime95 or CPUBurn or the like, for short periods of time,
until you are satisfied that the system is cooled properly, and
stable at the new overclock. You should also, at some point, run
memtest86 from memtest86.com, to make sure the memory is really
solid - no sense fighting other problems when it is really the
memory at fault.

HTH,
Paul

Yep, you were right.... I dropped my memory clock to 320, then raised my FSB
to around 250 MHz. My machine started to levitate.... Since I am a bit
cowardly, I dropped the speed down until the CPU was runing at 3.4 Ghz, and
everything seems to be stable with some safety margin thrown in. My Twin X
can handle the more agressive memory timings with the "PAT - like" bios
features activated. I guess my next step will be to run memtest on it. What
really impresses me the most is the Zalman 7000CU heatsink - under normal OC
operation things get only 2~3 C hotter. Even when I ran the ATI Lava tubes
screensaver all night, the processor didn't go higher than 36 C, and quickly
cooled down. Its the best 40 dollar investment I have made so far. Thanks
for the info.