DDR PCXXXX speed to P4 FSB question

[Cat]

I haven't paid attention to DDR RAM much in the past few years, as I'd been using RDRAM in my late TH7-II. What DDR speeds are required by the 400, 533, and 800 MHz P4s? Thanks for tolerating my silly question.

 

[Lonyo]

P4 with 400MHz QPB runs 100MHz FSB, so you need 200MHz DDR - PC1600
P4 with 533MHz QPB runs 133MHz FSB, so you need 266MHz DDR - PC2100
P4 with 800MHz QPB runs 200MHz FSB, so you need 400MHz DDR - PC3200

You can go with higher numbers to allow you to overclock, and I don't know of anywhere you can get PC1600 really, entry level is PC2100 now.

 

[Tom]

P4 motherboards use ratios of memory speed and cpu speed, so it isn't limited to just those options.

For example with a 200mhz FSB P4(800fsb quad pumped) and motherboard you can use

1:1 ratio which requires DDR400(also known as pc3200)
5:4 ratio which requires DDR320(slightly underclocked DDR333 also known as pc2700)
3:2 ratio which requires DDR266(also known as pc2100)

 

[Cat]

Dividers suck, however. : )

 

[Budman]

Originally posted by: Cat
Dividers suck, however. : )

Do they?

Really?

 

[Cat]

Yes, they do.

 

[Duvie]

Originally posted by: Cat
Yes, they do.

Hows that???

I man ultimately 1:1 to always be the wiser choice but if it meant stopping your oc at 100-200mhz slower clockspeed then that is plain stupid and you know nothing about performance on a P4 system!!!

I and some have ran the test and know this....

One area dividers can suck and this is on a case by case or mobo by mobo instance is some dividers will not work after certain fsb or that GAT or PAT is unattainable...Do your research and this is not a problem....

 

[Duvie]

Originally posted by: Lonyo
P4 with 400MHz QPB runs 100MHz FSB, so you need 200MHz DDR - PC1600
P4 with 533MHz QPB runs 133MHz FSB, so you need 266MHz DDR - PC2100
P4 with 800MHz QPB runs 200MHz FSB, so you need 400MHz DDR - PC3200

You can go with higher numbers to allow you to overclock, and I don't know of anywhere you can get PC1600 really, entry level is PC2100 now.

YOu should point out these are DUAL CHANNEL DDR configurations with boards like i865/i875 or sis655 being the only official option fro the later two and definitely the latter one.

SINGLE CHANNEL configurations can work but the ram cannot successfully feed the bandwidth of the P4 and that is why Dual channel is the most efficient use of with a P4.

 

[beatle]

Dividers aren't the end of the world, and are nice if you're upgrading and want to keep your existing ram. But since you're starting from scratch, get the PC3200 and that 2.8C.

 

[Cat]

Good lord, I was kidding, it's why I had a smiley at the end of my second post. : )