Ram Bandwidth

[mpo26]

I don't really have an understanding of settings for motherboards etc. but I was hoping one of the experts on here could give me some pointers to what's wrong with my memory performance.

On running Sandra Lite, my memory bandwidth benchmark is only 5000 when systems less powerful overall are getting 9000 and much faster PCs well above this. All other benchmarks seem OK and I've experimented with the BIOS but still no luck.

My motherboard is Asus P5Q.

Here are my settings:

 

[Minstadave]

Its probably the low bus speeds, your memory is running at 400mhz, whilst the FSB is only at 266mhz.

Try upping the FSB to 400mhz and running the memory at 400mhz too. You'll probably have to drop the CPU muliplier a bit initially.

 

[mpo26]

I thought the FSB might be the case, but in doing some research it seemed a lot of people with Q6600s had their FSB at 266 too. I didn't want to change anything which might cause problems.

 

[Minstadave]

I can't see anything wrong in CPU-Z, could be a Sandra bug, have a go with Everest and see what that shows.

 

[BigglesPiP]

Its probably the low bus speeds, your memory is running at 400mhz, whilst the FSB is only at 266mhz.

Try upping the FSB to 400mhz and running the memory at 400mhz too. You'll probably have to drop the CPU muliplier a bit initially.

Although 400x6 == the stock 2400MHz, and the P45 is quite capable of 400MHz.

I don't think this is the problem, Throughput wise; you have a 1066Mhz FSB, and your memory is 800MHz.

Nothing is wrong with your memory settings, it's just you have poverty spec PC2-6400.

 

[mpo26]

In Everest:

Memory Read: 5619mb/s
Memory Write: 2395mb/s
Memory Latency: 91.0ns

 

[BigglesPiP]

My PC2-7600 (DDRII950) @ CL5-5-5-15 gets:

Read: 7125 MiB/s
Write: 2586 MiB/s
Latency: 66.9 ns

Your results for PC2-6400 are about right going by that.

 

[Minstadave]

I benched my 4x2GB of PC6400 running at 940Mhz and I got:

Read 7866MB/s
Write 3238MB/s
Latency 62.3ns

So your figures look fine.

 

[BigglesPiP]

I benched my 4x2GB of PC6400 running at 940Mhz and I got:

Read 7866MB/s
Write 3238MB/s
Latency 62.3ns

So your figures look fine.

that's not PC2-6400, it's PC2-7520.

 

[Minstadave]

The RAM is OCZ PC6400 overclocked to 940mhz.

 

[BigglesPiP]

PC2-6400 is a speed rating, it means DDR2 running at a theoretical 6400MB/s.

Your memory is running a theoretical bandwidth of 7520MB/s due to your overclock.

Edit:
There was never memory capable PC6400. Bit much for DDR really.

 

[Minstadave]

PC2-6400 is a speed rating, it means DDR2 running at a theoretical 6400MB/s.

Your memory is running a theoretical bandwidth of 7520MB/s.

Thank you for pointing out the obvious, it is however an OCZ PC6400 kit.

 

[BigglesPiP]

No it isn't, it's branded as PC2-6400.

 

[Minstadave]

Dear god.....

 

[Yamahahahahaha]

I lol'd at this argument.

Anyway, higher frequency memory = more bandwidth.
Timings matter so little these days, or rather the processors are designed to handle relatively high access latencies.

 

[BigglesPiP]

Dear god.....

Your fault for posting garbage about FSBs.

 

[Minstadave]

Your fault for posting garbage about FSBs.

None of that was garbage, if he wants to increase his memory bandwidth increasing his FSB will do just that.

Unfortunately I can't help that you're a bit on the spectrum.

 

[simonnance]

Do we have to find you two a padded room to fight this one out in?

Anyway, as far as the OP is concerned that isnt bad, if you want to max your bandwidth you can try tweaking the freq up a bit, or OC that Q6600 and get the divider down to 1:1, should give you anything from 2800Mhz CPU (7x400) to 3800Mhz CPU (9x400). Then you can try tweaking out those timings while keeping stability, and if you want to get really hardcore play with the sub-timings (there are some good guides around somewhere). That mobo should give you a lot of options to play with.

 

[Big.Wayne]

I don't really have an understanding of settings for motherboards etc. but I was hoping one of the experts on here could give me some pointers to what's wrong with my memory performance.

You would get better bandwidth if you could either overclock your ram or just buy some PC8500.

In that set-up you would want your ram running at least 533MHz (DDR2-1066) to keep up with your System Bus . . .

 

[gordan]

Actually, FSB makes a massive difference to RAM bandwidth on systems that actually have an FSB (unlike all 64-bit AMD chips and Nehalem). It provides better RAM pipeline saturation by reducing the effect of latencies through better pipeline packing.

Also, be prepared to accept that a relatively feeble AMD chip (e.g. an Athlon X2 running slower than your Q6600) will absolutely murder a Core2 of any denomination on memory bandwidth because AMD chips have the MCH (Memory Controller Hub) built into the CPU itself, which has a massive impact on reducing memory latencies and thus increasing throughput (there's no FSB in the way!). My DDR3-1600 Q6600 gets about 8.5GB/s when tuned to within 1% of death. At the same time, my DDR2-1066 Phenom 9950 gets about 11.5GB/s with memory that is a third slower. 5-5.5GB/s seems about right for a Core2 with DDR2-800.

Sandra reference systems are usually some of the most highly tuned systems you can find, and may not even be stable for more than benchmarking at the settings they are running. Maybe it's just a conspiracy theory, but the fact that Sandra offers to list sources and prices of components used might imply that it is in their interest to make people think that their system isn't as fast as it could be and that they should upgrade. It wouldn't surprise me if there was referral/commission on the sales generated in this way.