If I have a 400MHz FSB, can I use DDR 400 RAM?

[KingNothing]

I have a HP dv1000 laptop (warning enormous PDF link).

According to this document, my laptop has a 400 MHz FSB, but was shipped with DDR 266 RAM. Crucial's website offers me DDR 333 RAM as an upgrade and nothing else. Newegg sells DDR 400 RAM but of course doesn't say what it may or may not be compatible with.

So...is DDR 400 RAM the fastest RAM my computer can use? If I got DDR 400 RAM how would I confirm that it's actually running at 400MHz, and not 333Mhz? The BIOS only says how fast the processor is.

 

[Jiggz]

Yes, you can use them but you will not be able to harness the full capability of the DDR400 ram. Technically, your FSB is only 100 Mhz while your rams ran at 133 Mhz. DDR 333 is rated at 166 FSb while DDR 400 is rated at 200 FSB. I'll say you are good enough to buy the DDR 333 unless you are preparing for the future where you might get a 200 FSB (800 MHZ FSB, which is basically 200 MHZ quad pumped, X4), then you can get the DDR 400.

 

[KingNothing]

Originally posted by: Jiggz
Yes, you can use them but you will not be able to harness the full capability of the DDR400 ram. Technically, your FSB is only 100 Mhz while your rams ran at 133 Mhz. DDR 333 is rated at 166 FSb while DDR 400 is rated at 200 FSB. I'll say you are good enough to buy the DDR 333 unless you are preparing for the future where you might get a 200 FSB (800 MHZ FSB, which is basically 200 MHZ quad pumped, X4), then you can get the DDR 400.

There's no preparing for the future...it's a laptop. Can't exactly replace the motherboard to get a faster FSB.

So it sounds like there's no performance benefit with DDR 333 either?

 

[Jiggz]

You can if you buy rams with the lowest latency possible. Usually, ram with a CAS latency of 2.0 will give you about 10% performance gain compare to a 3.0 cas. And if you are running Win XP, you might want to get at least 768 MB or 1Gb of ram. This will minimize your pagefile access thus increasing performance.