AMD64 and PC2700 DDR?

[Jediab]

I saw a computer for sale in an add from a local computer chain and it had an AMD64 3000 (not a Sempron) with PC2700 memory in it. So I then wondered, is this computer being underclocked? I am not an expert at the AMD64 settings, so I was wondering what would be needed to be done to make this work. And if it is possible, what sort of stress (if any) would there be and on what?

Thanks for your insight!

 

[Dkcode]

The cpu wont be underclocked. The memory will run along @ 166mhz and the cpu will run at its default 200mhz. There is no performence loss when the ram and cpu are running at different bus speeds becuse the memory controller is located on the cpu.

 

[Jediab]

Originally posted by: Dkcode
The cpu wont be underclocked. The memory will run along @ 166mhz and the cpu will run at its default 200mhz. There is no performence loss when the ram and cpu are running at different bus speeds becuse the memory controller is located on the cpu.

Ahh ok I am starting to see what you are saying.

If there isnt any performance loss if the memory and cpu are running at different speeds, what is the benefit to memory running at above 200mhz?

 

[Lonyo]

There is a slight performance loss, but it's not that huge.

 

[dguy6789]

Originally posted by: Jediab

Originally posted by: Dkcode
The cpu wont be underclocked. The memory will run along @ 166mhz and the cpu will run at its default 200mhz. There is no performence loss when the ram and cpu are running at different bus speeds becuse the memory controller is located on the cpu.

Ahh ok I am starting to see what you are saying.

If there isnt any performance loss if the memory and cpu are running at different speeds, what is the benefit to memory running at above 200mhz?

There really is no benefit other than the ability to brag about how your ram and bus speed are 1:1 ratio.

 

[n7]

Unfortunately, a lot of brand name computers have been doing that sort of thing (running slower RAM with a faster CPU by using a divider) for many years.
Fortunately, on A64s, the performance hit isn't too bad.

 

[BitByBit]

Originally posted by: Jediab
If there isnt any performance loss if the memory and cpu are running at different speeds, what is the benefit to memory running at above 200mhz?

Higher memory speeds give the processor access to more bandwidth, but with the K8 platform, the very low memory access latency actually reduces the need for a higher peak bandwidth, except for certain tasks such as encoding.
Bandwidth only really becomes a bottleneck as clock speeds increase, since the processor can get through more instructions/data per second, and therefore needs to receive its instructions at a higher rate.

If this is a dual-channel Athlon 64 3000+, then running it with PC2700 memory will make a negligable impact on performance, since it is being fed sufficiently quickly.
If it is a single-channel, socket 754 Athlon, then it will have more of an impact.

 

[theMan]

with a64's, the memory controller is in the cpu, so, every memory, and memory setting uses a "divider". its just that pc3200 is the highest divider so everyone uses that. when you run your ram 1:1, this isnt actaully 1:1 because the a64 doesnt have an fsb. it has hypertransport which runs at 100mhz. and no ones ram runs that fast. what 1:1 really means, is with that the memory divider, (cpu speed/a number) "a number" the same as the cpu multi, so it runs with the htt. a lower divider just means that "a number" is bigger than the cpu multi. its not like other systems where there is a fsb that controlls the memory, and if you slow it down, you have to block it up, there is always a divider, until you can have memory that runs the same speed as the cpu.

 

[BitByBit]

Originally posted by: theman
with a64's, the memory controller is in the cpu, so, every memory, and memory setting uses a "divider". its just that pc3200 is the highest divider so everyone uses that. when you run your ram 1:1, this isnt actaully 1:1 because the a64 doesnt have an fsb. it has hypertransport which runs at 100mhz. and no ones ram runs that fast. what 1:1 really means, is with that the memory divider, (cpu speed/a number) "a number" the same as the cpu multi, so it runs with the htt. a lower divider just means that "a number" is bigger than the cpu multi. its not like other systems where there is a fsb that controlls the memory, and if you slow it down, you have to block it up, there is always a divider, until you can have memory that runs the same speed as the cpu.

Hypertransport has nothing to do with the memory interface.
There is no HT link between the processor and memory!
The K8, like the K7, uses the double-pumped EV6 bus, which runs at a fraction of the processor clock, using a divider to do so. This usually results in a native speed of 200MHz, or 400MHz effective.
That Athlon will therefore most likely be running on a 200MHz bus (note I said bus, not 'FSB'), but the memory in this case is running at 166MHz. Usually, an Athlon 64 is paired with PC3200 memory to allow a 1:1 ratio, even though this is not really necessary, especially at lower processor clocks.
Once Athlons start reaching 3.0GHz, PC3200 memory will start to become a bottleneck, even in dual-channel mode. This is why AMD is switching to DDR2; DDR(1) at its current speeds will not be able to supply the Athlon with its required data sufficiently quickly as clock speeds exceed 3.0GHz, resulting in pipeline bubbles.

 

[theMan]

wow, i got pwned.

 

[Jediab]

Great info everyone. Thanks for your time and effort in posting.