NV45 spotted @ Anand

[Joe DeFuria]

Regarding bandwith issues... the XTs and Pros I've seen so far all had 1.6ns and 2.0ns modules, respectively. Now if BW was such an issue, why would reference cards be underclocked like this (1120MHz instead of 1250, 900MHz instead of 1000MHz)?

The same reason why graphics card ram is typically underclocked a bit: presumably lower failure rate and lower power consumption.

 

[anaqer]

"Lower failure rate"?
It's specified to run at that rate, is it not? I mean, if it won't run reliably at 1GHz, how could Samsung get away with labeling it -20 ? And what does a ~10% higher clock matter in power consumption with GDDR3 - or are they running a power budget this tight?

Underclocking IS typical - on production boards, usually because better memory has become available since the introduction, but manufacturers choose to run it at reference values (well, most of them).

 

[Joe DeFuria]

I mean, if it won't run reliably at 1GHz, how could Samsung get away with labeling it -20 ?

That all depends on how Samsung guarantees the operation. The single chip in isolation? The module paired with other ones on the same PCB running with an ASIC? With what kind of "power" (how clean?) For what length of time, and with what typical usage? With what cooling?

Let me reverse the question to you. If there is NO DOWNSIDE to releasing the X800 Pro with memory at 500 Mhz vs. 450....why doesn't ATI do it? Surely, there is nothing but a potential for better performance in at least some situations?

Underclocking IS typical - on production boards, usually because better memory has become available since the introduction, but manufacturers choose to run it at reference values (well, most of them).

I don't get you...for quite some time "production boards" have been shipped with memory "underclocked" based on the ns rating. Years....

 

[anaqer]

I don't get you...for quite some time "production boards" have been shipped with memory "underclocked" based on the ns rating. Years....

Is that not exactly what I said?

If there is NO DOWNSIDE to releasing the X800 Pro with memory at 500 Mhz vs. 450....why doesn't ATI do it?

Uhm... that was sorta the question, right? ATi can afford underclocking --?--> Why the wait for the magical 800MHz modules?

 

[Mintmaster]

anager, sometimes the maximum RAM speed is at the cost very long latencies. The computations involved in graphics is very suitable to absorbing latency by making long FIFOs in the pipelines, but these cost significant die area. You can only make them so long, and there's a point where you'd rather just get better RAM and either save those transistors or devote them elsewhere.

It's all about tradeoffs. I'm not sure if this is indeed the reason, but it's possible.

 

[Joe DeFuria]

If there is NO DOWNSIDE to releasing the X800 Pro with memory at 500 Mhz vs. 450....why doesn't ATI do it?

Uhm... that was sorta the question, right?

Right, to which the answer is : There IS a downside to running Ram "at the rated speed", otherwise ATI would do it.

 

[anaqer]

Right, to which the answer is : There IS a downside to running Ram "at the rated speed", otherwise ATI would do it.

And this downside seems to be bad enough to counter the BW gains - which would translate into BW limitations being fairly minor, meaning, there's not much to be gained by using faster memory later on.

Mintmaster, thanks for the headds up on latency I forgot about that.

 

[Nite_Hawk]

And this downside seems to be bad enough to counter the BW gains - which would translate into BW limitations being fairly minor, meaning, there's not much to be gained by using faster memory later on.

Mintmaster, thanks for the headds up on latency I forgot about that.

that doesn't translate into BW limitations being minor, it just means that ATI didn't see a need for the card to have faster memory throughput than it already does. Perhaps they specifically arn't clocking the memory faster simply because the card is already fast enough for the intended market, and they now have a potential card upgrade (perhaps paired with a minor clock increase).

I think the problem with your assumption is that ATI really isn't in the business of producing the fastest card possible, only to produce the fastest card on market. It makes very little sense for them to produce anything significantly better than NV.

edit: fixed quote

Nite_Hawk