FSB-P4C800-E Del

[jimg]

This Asus P4C800-E Deluxe had one DDR400/512mb in Slot A1, and the post read "DDR 400 Single Channel or Virtual, linear mode". We added another exact duplicate (Kingston's KVR400X64C3A/512) in Slot B1. The post screen now reads "DDR 400 Dual Channel Linear ...". Shouldn't this now read 800?

Secondly, what tool can I use to confirm the 800? (Windows XP Pro.)

 

[Crashman]

No, it should read 400. It's DDR400 RAM. It has a 200MHz clock rate and transfers data twice per clock for a data rate of 400MHz. The thing to look for is the "dual channel" message, which you're getting. That means the bus is now 128-bits rather than 64-bits wide.

Having the bus speed twice as wide means you have twice the transfer rate at the same clock speed. Since the memory is still running 200MHz clock rate (400MHz data rate), the message remains DDR400.

The P4 CPU bus (800 bus) is 64-bits wide. Quad Data Rate allows it to transfer data 4x per clock cycle. So it also runs 200MHz clock rate, but with an 800MHz data rate.

Because the memory bus in dual channel mode is twice as wide as the CPU bus, DDR400 at 128 bits has the same transfer rate as the QDR800 CPU bus of 64-bits.

So I've covered this from a couple angles so you'd understand why 128-bits (Dual Channel) doubles the transfer rate (Megabyts/Sec) without increasing the frequency (Transfers/Sec). The number of transfers per second is the same, it's just that twice as much data goes through per transfer.

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[jimg]

Thanks very much, very clear!

 

[Crashman]

Thanks, I've been working on clarity for years!

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>