Any possibility of DDR2 with Nehalem?

[Idontcare]

Originally posted by: VirtualLarry

Originally posted by: Idontcare

Originally posted by: nerp
Watch ASRock come out with a board with DDR2 and 3 memory slots.

I pity the fool who spends the $$ on a Nehalem to turn around and cripple the system by choking it with a bunged-up dual-channel DDR2 mobo.

Penryn is pretty much indifferent to the DDR2/DDR3 business end of the mobo thanks to the prefetchers and massive L2$...Nehalem will no doubt be a tad more sensitive to the memory sub-system if you actually intend to utilize the CPU.

Are you suggesting that Intel has left out all of the tweaked prefetch logic that is present in Penryn, in Nehalem? That would seem strange to me.

Not by any stretch of the imagination am I suggesting that.

But the engineers certainly designed the chip to require a certain bare minimum bandwidth to go along with the low latency of the IMC...drop below that minimum and you will no doubt bottleneck the CPU's abilities provided you are doing something with those 8 threads beyond checking email and uploading photos to snapfish.

What I am suggesting is that this bare minimum bandwidth ought to lie somewhere above dual-channel DDR2-1066 and below dual-channel DDR3-1333.

If the minimum lies any lower than that it would imply Intel wasted valuable xtor's (needlessly bloating the Nehalem die) in beefing up prefetchers and L3$ by designing for a bare-minimum bandwidth that likely will easily be surpassed by mainstream systems.

If DDR2 is good enough to support 8 threads at peak utilization then it would also imply that triple-channel DDR3 provides negligable benefit to bloomfield out of the gate, which I highly doubt will be the case.

And if triple-channel DDR3 provides noteworthy benefit then not having triple-channel DDR3 ought to provide a noteworthy performance degradation.

Are my suggestions any clearer now?

 

[BTRY B 529th FA BN]

Triple channel... what I am wondering is if us people with a pair of dual channel DDR3 ...will the memory vendors sell a single stick to us that have a pair already? then on top of that, what are the chances of getting the same IC

 

[VirtualLarry]

Originally posted by: Phynaz
But to answer your question, When an AMD cpu needs to access memory that is connected to another cpu, it talks to the HT controller on the other cpu, which sends the request through the crossbar switch to memory controller. Once the data is retrived by the second cpu's memory controller, it is passed to the HT controller through the crossbar switch and on the HT controller of the requesting cpu.

Here's another bit of info for you, in any AMD system with more than two sockets - other than a K10 based Opteron - there aren't enough HT links for all the cpu's to talk to each other. Therefore if cpu 1 needs access to memory that's connected to cpu 3, the request has to go by way of cpu 2, as there is no connection between 1 and 3.

So in other words, AMD CPUs CAN access RAM via the HT bus. Which is what I originally said.

Not to mention, when the system boots, it goes to address FFFFFFF0 (IIRC), and starts executing code there. That's the system BIOS, in ROM, but the AMD CPU has to access that via the system chipset, over the HT link. So if it can access ROM memory over the HT link, there's no reason that it can't access RAM memory over the HT link too - as long as the system chipset speaks HT, and contains a DRAM controller.

 

[Phynaz]

You're still not getting it. An AMD cpu can access another cpu via HT.

HT is not a memory interface.

Did you even bother to look at the link I provided?

 

[aigomorla]

i hate to say this because it makes me sound really snobby but its true.

If you cant afford DDR3, you cant afford neha.

By the time DDR2 boards come out for neha, it will be very very long time. (try somewhere between 1-2yrs)

So, if your trying to cheap out of neha by using DDR2, this thread is an oxymoron itself.

 

[imported_Woody]

Unless AMD pulls some magic out of it's /\55 in the next year Intel has no reason to introduce low end Nehalem at launch. Socket LGA 775 will be the low end for the next year or so at least.