I'm making the switch to 775, need some education on DDR2

[MechaSheeba]

I never paid much attention to DDR2 when it first came about, so I'm pretty much out of the loop here. I didn't think I'd ever be using a 775 setup, but with dual core becoming so affordable, I decided to bite.

So DDR2 400/533/667, is it basically the same as DDR 400/533/667? I don't see how that can be the case, because what 775 chip is capable of 333mhz fsb?

Or is it like quad data rate, instead of double? Could somebody explain the basics to me in relation of DDR? Or provide a link, my Google skills are pretty weak.

 

[InlineFour]

Socket 775 has a FSB of 800MHz. The FSB is quadpumped so it's really 200MHz FSB. (200 x 4).

Don't worry about DDR and DDR2 for now. DDR400 is 400MHz so divide by two (double data rate) 2. You get 200MHz, which is the same FSB as the P4. DDR2 is is just the same thing.

So unless you're going to overclock, just buy DDR2 400.

 

[MechaSheeba]

Oh ok, so it's the same exact thing as DDR, just capable of much higher clocks? Why the hell do people buy DDR2 667 then? They'd never make use of it?

Or is it designed to be run in like a 3:4 with DDR2 533 etc.?

 

[alimoalem]

Originally posted by: MechaSheeba
Oh ok, so it's the same exact thing as DDR, just capable of much higher clocks? Why the hell do people buy DDR2 667 then? They'd never make use of it?

Or is it designed to be run in like a 3:4 with DDR2 533 etc.?

same reason people buy DDR500: the ram is supposed to run at least as fast as the specified clock speed and at the timings it is rated for. so when you buy DDR500/DDR2667, it comes at a speed of DDR400/DDR2 400 but you are supposed to be able to run it at DDR500/DDR2 667.

 

[MechaSheeba]

Originally posted by: alimoalem

Originally posted by: MechaSheeba
Oh ok, so it's the same exact thing as DDR, just capable of much higher clocks? Why the hell do people buy DDR2 667 then? They'd never make use of it?

Or is it designed to be run in like a 3:4 with DDR2 533 etc.?

same reason people buy DDR500: the ram is supposed to run at least as fast as the specified clock speed and at the timings it is rated for. so when you buy DDR500/DDR2667, it comes at a speed of DDR400/DDR2 400 but you are supposed to be able to run it at DDR500/DDR2 667.

Yeah but DDR500 = 250mhz fsb, a lot of P4 chips can hit that. DDR2 667 = 333mhz fsb, correct? Are there chips capable of those speeds? Or is DDR2 meant to be run asynchronously with the CPU? Is that how most users have their 775 rigs set up?

 

[stevty2889]

DDR-2 Usualy runs asynchronosly from the FSB. For example, my 805 is running at 3.7ghz(185mhz FSB), but the ram is still running at 667mhz(equivilent to 333mhz FSB). DDR-2 is still double data rate just like DDR, it has higher clock speeds, but also higher latencies. So DDR2-400 runs at 200mhz, DDR2-533 @ 266mhz, DDR2-667 @333mhz, DDR2-@800 400mhz.

 

[bamacre]

If you are wanting 2GB, get this...
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=80098-45

Or 1GB, get this...
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=85016-33

 

[MechaSheeba]

Ah ok, I get it now, thanks guys.

 

[zephyrprime]

DDR2 usually runs synchronously with FSB in retail computers. Some overclockers runs DDR2 asynchronously to attain higher CPU clock speeds with slower ram. Some P4's run with a 1066FSB so with these systems, DDR2 666 is useful to overclock and maintain synchronous fsb speeds.