DDR 400 with 533 FSB CPU?

[+Steve B Subscriber²]

Is it at all possible to have a 533FSB CPU and get full usage out of DDR 400 RAM?

[CDog]

yup

[Iluvatar]

The 533mhz FSB operates with 266mhz DDR i believe. no problems with anything higher though.

[Max Veteran]

If you are running single channel DDR400....you wont get max use because its not running the 533Mhz that it should.

If you are running Dual Channel DDR400 then it will - as it willl be able to run any CPU up to 800mhz FSB without any bottlenecks.

If you ARE using dual channel - it will downclock to dual channel DDR266 - as 266*2 = 533mhz (DDR266 was designed for the 533 bus P4)

EDIT: Make sure your mobo is compatible with the DDR400 memory. Though it should work.

Edited June 6, 2004 by absolutemaxpayne.co.uk

[CDog]

Good point about the single/dual channel DDR400 - I tend to only think in terms of dual channel :)

[Zip]

you get your best performance running your ram:cpu at 1:1 ratio so if your cpu is at 133 then you will not need any more than pc2100 (266mhz), unless you plan on overclocking.

[PCKing]

  Iluvatar said:

The 533mhz FSB operates with 266mhz DDR i believe. no problems with anything higher though.

My 533mhz FSB supports PC2700 or DDR333 memory...

You should find in the BIOS to set the speed of memory higher than 266 or 333... not sure that 400 is an option but I know you can set it higher.

[mstx]

If it's a P4: You have to devide 533 by 4 because a P4 uses 4x the FSB speed.

533/4 = 133mhz.

So actually you wouldn't need PC3200 at all.

[Max Veteran]

You do not need DDR333 or DDR400 to run a P4 533Mhz bus.. It needs dual channel DDR266, thats final. Anything more than that is a bonus for overclocking. Anything less is just a bottleneck.

Only the latest Pentium 4's have a quad pumped FSB, not the 533mhz revisions.

200*4=800mhz fsb. Thats why we need DUAL channel DDR400 so that It reaches the 800mhz the chip requires.

This is how I would like to think of it:

Dual channel DDR266 was designed for the P4 533mhz.

Dual channel DDR400 was designed for the P4 800mhz.

Single channel DDR266 was designed for the older Athlon chips (Thoroughbred - 266mhz fsb)

Single channel DDR400 for the newer Athlon chips.

Single channel DDR333 is for the later Athlon Barton chips, which actually ran at 333mhz.

Note: There is no Dual channel DDR333 because no chip runs at 666Mhz FSB!

[+Steve B Subscriber²]

The reason why i was asking was because my MB died a couple of days ago. I do NOT have the money to buy the more exspensive stuff right now. So I need one that is cheap but works fine and that I can buy it new. So I was looking at a board with the i848P chipset. Is anyone familiar with that chipset and does it support dual channel ddr? I saw a MB on newegg.com and it seems to support it. Although, I am not sure. Can anyone tell me? Thanks for your help.

[Max Veteran]

What board is it? Because some boards limit chipset features.

[Nathanael]

  absolutemaxpayne.co.uk said:

You do not need DDR333 or DDR400 to run a P4 533Mhz bus.. It needs dual channel DDR266, thats final. Anything more than that is a bonus for overclocking. Anything less is just a bottleneck.

Only the latest Pentium 4's have a quad pumped FSB, not the 533mhz revisions.

200*4=800mhz fsb. Thats why we need DUAL channel DDR400 so that It reaches the 800mhz the chip requires.

This is how I would like to think of it:

Dual channel DDR266 was designed for the P4 533mhz.

Dual channel DDR400 was designed for the P4 800mhz.

Single channel DDR266 was designed for the older Athlon chips (Thoroughbred - 266mhz fsb)

Single channel DDR400 for the newer Athlon chips.

Single channel DDR333 is for the later Athlon Barton chips, which actually ran at 333mhz.

Note: There is no Dual channel DDR333 because no chip runs at 666Mhz FSB!

Xeons have a bus of 667MHz.

[PCKing]

  absolutemaxpayne.co.uk said:

You do not need DDR333 or DDR400 to run a P4 533Mhz bus.. It needs dual channel DDR266, thats final. Anything more than that is a bonus for overclocking. Anything less is just a bottleneck.

Only the latest Pentium 4's have a quad pumped FSB, not the 533mhz revisions.

200*4=800mhz fsb. Thats why we need DUAL channel DDR400 so that It reaches the 800mhz the chip requires.

This is how I would like to think of it:

Dual channel DDR266 was designed for the P4 533mhz.

Dual channel DDR400 was designed for the P4 800mhz.

Single channel DDR266 was designed for the older Athlon chips (Thoroughbred - 266mhz fsb)

Single channel DDR400 for the newer Athlon chips.

Single channel DDR333 is for the later Athlon Barton chips, which actually ran at 333mhz.

Note: There is no Dual channel DDR333 because no chip runs at 666Mhz FSB!

400mhz FSB = 100x4

533mhz FSB = 133x4

800mhz FSB = 200x4

All Pentium 4's are quad pumped FSB.

Put a 533mhz chip on a board with dual channel memory and it will take DDR333 running in dual mode

Put an 800mhz chip on a board with dual chanel memory and it will take DDR400 running in dual mode

Why is it so hard to beileve this? I have 333 memory on my 533 FSB chip and its recognized and runnning at 333...

"Note: There is no Dual channel DDR333 because no chip runs at 666Mhz FSB!"

- Put a 533 FSB chip on an 800 FSB motherboard and you will be able to run DDR333 in dual channel mode.

[Max Veteran]

  PCKing said:

Why is it so hard to beileve this? I have 333 memory on my 533 FSB chip and its recognized and runnning at 333...

Yeah, I didn't say that it wouldn't work, im saying that it is not neccessary. Like I said, anything is a bonus over DDR266 because 266*2 = 533.

  Quote

- Put a 533 FSB chip on an 800 FSB motherboard and you will be able to run DDR333 in dual channel mode.

Again, it will run DC DDR333, but it still doesn't need DC DDR333. It only needs DC DDR266.

[Max Veteran]

  Jerry J. said:

Xeons have a bus of 667MHz.

I was talking about desktop procesors, but okay, point taken. I don't know a lot about Xeons.

[nonick]

err dual channel got nothing to do with CPU FSB speed. FSBs are the same for single and dual channels.

[ANova]

fsb = 133 MHz x 4 = 533 MHz bus

Dual channel allocates each memory stick it's own channel to operate on rather then sharing one channel. You can think of it as a 3 lane road being expanding into two 3 lane roads; the ultimate purpose being to alleviate any bandwidth limitations that might occur while using single channel. Dual channel has nothing to do with memory operating frequency. DDR266 can operate in both single channel and dual channel assuming the motherboard allows it, it does not increase to DDR333 in dual channel.

To answer the thread starter's question. PC3200 (DDR400) will work perfectly fine with a P4B, it will just run at a slower clock speed. Memory can always run at speeds less then what it was made for, it cannot be run at speeds greater then what it was meant for. The only thing I'd suggest is you use a newer motherboard that supports all the cpus for compatibility reasons. Some of the older motherboards may have trouble with newer and faster ram.

[bigdawgfoxx]

Yah...800Mhz FSB is really 200X4, so PC3200 runs at 200 (DD equals 400)