Terrible memory performance


D

don't look

Just put together a system based on the Nforce 4,AMD64 4000 1Mb cache and
1GB PC3200 DDR(2x512).
The ram modules aren't a match but the both have the same spd timings.One is
single sided,one double.
Running Sisoft 2007 memory bandwidth test I'm getting 2699 and 2698.
This seems very low to me. Some other benchcmarks show somewhat better
system performance though.
3DMark 05 shows around 7300 and a Sisoft hard drive benchmark is around
56mb. I don't think running with mismatched ram could cause this much of a
lag? Any ideas?Thanks
 
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J

John Doe

don't look said:
Just put together a system based on the Nforce 4,AMD64 4000 1Mb
cache and 1GB PC3200 DDR(2x512).
Opteron 152
2x512 PC3200 (same brand/model, Kingston ValueRAM)
One is single sided,one double. Running Sisoft 2007 memory
bandwidth test I'm getting 2699 and 2698.
6314, 6344
Sisoft hard drive benchmark is around 56mb.
60 MB per second (10,000 RPM Raptor)
 
P

Paul

John said:
Opteron 152
2x512 PC3200 (same brand/model, Kingston ValueRAM)


6314, 6344


60 MB per second (10,000 RPM Raptor)
And based on those results, it almost looks like the OP is
in single channel mode for some reason.

When you think about it, a single sided 512MB DIMM uses
64Mx8 chips. A double sided 512MB DIMM uses 32Mx8 chips.
The rows by columns addressing is different for the two
chip types. The DIMMs are not matched.

AMD dual channel is not true dual channel. It is referred
to as "128 bit mode" versus "64 bit mode" in the AMD
documentation. In "128 bit mode", AFAIK both DIMMs must
be driven with the same addressing information, which
is not possible if they have different rows x columns.
(The Nforce2 chipset is an example of true dual channel,
and Nforce2 would not have had such a problem with those
two DIMMs.)

That means, the BIOS had to make a tough decision. Not
start the computer at all, or run it in single
channel. I think the BIOS made a good decision :)

To fix the problem, match the number of sides of the
memory. Either use two double sided ones, or use
two single sided ones, if you wish to benefit from
AMD's "128 bit mode". Place your pair of matched
DIMMs in A1,B1 or in A2,B2 slots. If you put two
matched DIMMs in A1,B2 for example, I think
that causes single channel mode as well.

Paul
 
D

don't look

And based on those results, it almost looks like the OP is
in single channel mode for some reason.
And the clue why is in the original post...

Conor


I'm absolutely running in Single channel mode. But,from what I've read it
shouldn't be more than a 10% hit on performance?
Or maybe the bigger problem is single sided and double sided?Thanks
 
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J

John Doe

don't look said:
I'm absolutely running in Single channel mode. But,from what I've
read it shouldn't be more than a 10% hit on performance?
Or maybe the bigger problem is single sided and double sided?
I would agree if they are both running at the same speed, there is
something wrong with getting less than one half the performance.

Why don't you try removing one stick.

By the way, my values are more like 5950 when not overclocked.

PC3200 Kingston ValueRAM
200 MHz FSB
2.5-3-3-8 memory timing
 
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