does santa rosa support 800mhz fsb?

how come all the new santa rosa laptops seem to be coming with pc2-5300 667mhz? i thought they supported faster 800mhz ram, or is it just that manufacturers dont have a good supply line for the faster ram?

 

According to this http://www.pcmag.com/article2/0,1895,2127390,00.asp article, notebooks with 800mhz ram modules will become available later this year.

 

The 800MHz you are thinking of is the new FSB speed of Santa Rosa processors.

Lots of santa rosa notebooks will still continue to use 667MHz ram, since apparently the difference between 800 and 667 MHz RAM is not worth the price.

 

My question to Intel but they could not answer it. I saw a few manifacturers like Zepto testing their systems with 800 MHz DDR2 modules, so it does work.

 

But it may come down to the oem boards. Remember a couple model generations back when there was a big stink over HP putting DDR333 in units designed to use DDR400? Consumers were up in arms that aftermarket purchased DDR400 ram would simply downclock to 333 speeds (due to board limitations).

 

Couple thing to understand here...

First, DDR2-800 is not running at 800mhz. The bus speed is half that, 400mhz.

Now, let me give you an overview of the FSB, and the relation between that and your ram speed.

These new chips are kinda like the e4x00 desktop series. In actuality, the FSB is 200mhz [not 800mhz], but 'quad-pumped'. Thus, 4x200=800, and you have an 800mhz FSB.

Now, the ram does NOT necessarily run 1:1 with your FSB speed. Instead your ram speed is determined by a ratio. Your ram speed is the product of both the FSB and that ratio.

So, for example in stana rosa systems...

Running on a 1:1 ratio with the 800mhz FSB C2D should result in a ram speed of DDR2-400. Now, clearly that would offer lousy memory bandwidth, so a different ratio is being used. I suspect in this case a 2:3 ratio is used, resulting in DDR2-600. Now, in a perfect world you could add DDR2-800 modules and it should kick the ratio up to 1:2. Its hard to say if that will actually work though.

From my own personal experience with P965 based desktop systems, you kinda see diminishign returns passed a certain point. The optimal configuration is to push the FSB as high as possible and keep the ram 1:1. In laptops this isn't possible, or practical. Anyway, back to the main point.

Don't sweat the difference. It won't make as large a difference as you might expect.

 

I'm confused. What is multiplied by 4 to get 800Mhz. I thought the FSB runs at 800Mhz, the RAM Bus runs at 400Mhz, and the RAM has a frequency of 800Mhz because it's DDR ram.

 

hey thanks guys for the clarification then

 

Its the same trick as used in DDR except with quad pumped bus each clock cycle is capable of transmitting 4 times the data compared to that of a conventional bus.

 

alright...simply said..
santarosa plaform supports DDR2-800mhz RAM?

 

No. 800MHz FSB yes, but only 667MHz RAM.

 

Hi.

so when 800mhz ram becomes cheaper, can i replace my 667mhz ram and will they run at 800mhz.

thanks

John

 

No. 667MHz ONLY.

 

It's the chipset that doesn't support 800 MHz RAM.

From what I've heard, DDR2 800MHz isn't very energy efficient and that's why Santa Rosa dropped support for it. They're going for DDR3 800MHz on their next platform, Montevina, instead.

 

LOL

NO it does NOT support 800mhz memory

 

It would be a very easy fix. All we need to do is change the divider (FSB : DRAM) to 1:2.

 

I wonder what part of "NO" these people don't understand!

 

I wonder what part of "do not revive old posts" these newbies do not understand

K-TRON