Do I really need a 400MHz DDR memory for a 800 MHz P4 Processor?

[Phenom525]

I just want to know I should really get a DDR 400MHz memory for a P4 800MHz CPU. Or is a 333MHz DDR memory is good enough?

Thanks.

[Chuckiechan]

I'm not going to say whether you do or you don't. But I will give you an example.

I have a K7S5A Athlon 1600 OC'd to 1800. This board takes either DDR or PC ram. I took out my PC 512 and put in my DDR 512 (2600 ?) and noticed zero difference.

I do mainly Photoshop, Quake 2 on line, RTCW, plus the usual grunt work-excel, word, access.

I would try to get some returnable DDR to try first. Also, I'm not sure that chip/board will support the higher speed DDR without a BIOS upgrade. 800Mz is quite slow by todays standards. You might want to keep saving your money up to get a hotter chip/board combo and upgrade then.

BTW: Welcome to Techimo!!!

[Phenom525]

I'm sorry. I actually have a P4 2.4 GHz/512k Cache/800MHz FSB with HyperThreading processor. So I will try the 512MB PC2700 DDR 333MHz memory and see how that works out. Also, any experience/knowledge about Shuttle AB48PN mobo.

Thanks.

[RamonGTP]

Thats not a very good example for a couple reasons... First, the P4's benifit a LOT more from memory bandwidth than AMD's do. Secondly, the processor and board in question are a lot faster, and thus take better advantage of faster memory than a K7S5A and a 1600+ would...

That being said, yes you should be able to run it using PC2700 memory (at slightly reduced performance), so long as the motherboard has the correct FSB/Memory ratios

[jkrohn]

You realize that by running with PC2700 you are losing clock speed as well as memory bandwidth right?

PC3200 = DDR400 = 200 FSB = 800 FSB (P4) = 800*3 = 2.4 GHz
PC2700 = DDR333 = 133 FSB = 532FSB (P4) = 532*3 = 1.6 GHz

I think the multiplier is locked on those bad boys, so it will not auto adjust.

Jkrohn

[JohnE.]

I'd go with the PC3200. As jkrohn said, you'll lose a big whack of performance with the PC2700.

The 800MHz FSB on the P4 is actually 200MHz Quad-Pumped and is designed to run synchronously with DDR400 (200MHz Double Data Rate or; Double-Pumped). With PC2700 you'd be running the RAM asynchronously with the bus.

[Phenom525]

Thanks for the replies. I will get the PC3200 DDR 400 MHz memory.

[Ultima]

Jkrohn,

I don't know where you get the idea that a P4 would actually clock down to a 533Mhz fsb when paired with DDR333, but that is absolutely not true.

The dual channel would kick in for the extra bandwidth the P4 asks for, but the clcok speed of the P4 remains unchanged.

The P4 will benefit not only because of the 400Mhz ddr, but also cause of Intel's PAT technology.

Somewhere on Intel's site, I'll try and find the link, it says something along the lines of:

PAT is Performance Accelerating Technology, which means that when a P4 800Mhz version is paired with DDR400, the PAT is activated and gives about 5% extra performance.

Here is the link: http://www.intel.com/design/chipsets/pat.htm

Ultima

[WingWizard]

Get the 3200 mem; most people don't realize when they get this new awesome system that if they don't carefully select memory, you're severely hampering performance. I myself have pc3500 (433 mhz) memory for overclocking reasons