K8VSE Deluxe Slows with More Memory?

  • Thread starter Thread starter Wilburn Lee Baker
  • Start date Start date
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Wilburn Lee Baker

With 3 1Gig DDR-400 sticks, MemTest reports speed as DDR-267.
Remove one stick, MemTest reports speed as DDR-400!

Is this what's expected for this MB? Is there any way to maintain DDR-
400 while using all three?

THX
 
With 3 1Gig DDR-400 sticks, MemTest reports speed as DDR-267.
Remove one stick, MemTest reports speed as DDR-400!

Is this what's expected for this MB? Is there any way to maintain DDR-
400 while using all three?

THX
Click to expand...
Oh yes, that MB is an ASUS K8VSE Deluxe. Sorry.
 
Wilburn Lee Baker said:
Oh yes, that MB is an ASUS K8VSE Deluxe. Sorry.
Click to expand...

This will happen with all boards that use AMD 64bit CPU.
The memory controller is integrated on the CPU die.

Jim M
 
Oh yes, that MB is an ASUS K8VSE Deluxe. Sorry.
Click to expand...

What does Table 1 "Recommended memory configurations" in
the manual say ?

This is one reason I always recommend downloading a PDF
copy of the manual from the Asus web site, before you
buy. By reading the manual first, you'll know what
limitations the product has. (In this case, the table
in the manual is actually copied from some AMD documentation
and is a limitation of the memory controller inside the
AMD processor. A Socket 939 motherboard would have allowed
you to use a bit more memory - 4 sticks @ DDR400 but with
Command Rate set to 2T.)

Line 18 in the table is the "good configuration". Put
two DS DIMMs in slot 1 and slot 3, to get DDR400 on four
"sides" of memory. The entry on line 18 should work
slightly better than the entry on line 12.

Have you tried manually configuring the memory ? The BIOS
has automatically selected the memory speeds you noted
above, but you can try overriding them in the BIOS. Set
the Vdimm to maybe 2.75V to start, so the DIMMs have
enough voltage to work with, then increase the frequency
a bit. You can test the results with memtest86 from
memtest.org and with the torture test option of Prime95,
available from mersenne.org . If the BIOS has a Command
Rate setting, try setting it to 2T, as a tradeoff between
reduced memory bandwidth and increased stability.

And, if you get ambitious, and are thinking of getting
a S939 board - if you put 4 x 1GB into most desktop boards,
you will lose the use of ~1GB or so, to the need for
some address space for the AGP aperture and for the PCI
address space. PCI Express video even seems to be worse.
The Athlon64 supports memory hoisting, but yesterday
someone mentioned that a more expensive version of OS
might be required to work with it. So, if you are planning
on more than 3GB of memory, there are more issues
to deal with before it will work effectively. I guess
that means 2x512MB+2x1GB would be the largest
"cost effective" config for a S939 board.

Do you really need 3GB ?

Paul
 
What does Table 1 "Recommended memory configurations" in
the manual say ?

This is one reason I always recommend downloading a PDF
copy of the manual from the Asus web site, before you
buy. By reading the manual first, you'll know what
limitations the product has. (In this case, the table
in the manual is actually copied from some AMD documentation
and is a limitation of the memory controller inside the
AMD processor. A Socket 939 motherboard would have allowed
you to use a bit more memory - 4 sticks @ DDR400 but with
Command Rate set to 2T.)

Line 18 in the table is the "good configuration". Put
two DS DIMMs in slot 1 and slot 3, to get DDR400 on four
"sides" of memory. The entry on line 18 should work
slightly better than the entry on line 12.

Have you tried manually configuring the memory ? The BIOS
has automatically selected the memory speeds you noted
above, but you can try overriding them in the BIOS. Set
the Vdimm to maybe 2.75V to start, so the DIMMs have
enough voltage to work with, then increase the frequency
a bit. You can test the results with memtest86 from
memtest.org and with the torture test option of Prime95,
available from mersenne.org . If the BIOS has a Command
Rate setting, try setting it to 2T, as a tradeoff between
reduced memory bandwidth and increased stability.

And, if you get ambitious, and are thinking of getting
a S939 board - if you put 4 x 1GB into most desktop boards,
you will lose the use of ~1GB or so, to the need for
some address space for the AGP aperture and for the PCI
address space. PCI Express video even seems to be worse.
The Athlon64 supports memory hoisting, but yesterday
Click to expand...

Thank you for this insightful information. I am processing huge data
cubes in Matlab which dictate the raw need for 3GB. However, based on
your information, I'll attempt to use other techniques to get around
this requirement and process in 2GB.

Thank you.
 
Thank you for this insightful information. I am processing huge data
cubes in Matlab which dictate the raw need for 3GB. However, based on
your information, I'll attempt to use other techniques to get around
this requirement and process in 2GB.

Thank you.
Click to expand...

At least give the manual adjustment a shot first.
There is no way of knowing how far the memory speed
can be pushed, until you try. Maybe the three sticks
will go as far as DDR333. Or even DDR400.

The memory settings may look daunting at first, but
what you want to do, is take a few settings off auto,
so that the manual memory settings are shown. Then,
only play with the frequency setting for the memory,
and possibly the Command Rate 1T/2T setting, while
leaving all the myriad individual timing settings on
auto. As you change the memory frequency, the BIOS
will recompute the necessary memory timing settings,
based on the SPD info stored on each DIMM. So, only
setting a minimum of things to manual, will make the
adjustment process less painful.

Memclock Mode [Manual] should expose frequency choices.
Memclock to CPU Ratio DDR266, DDR333, DDR400
these are actually ratios, and the values shown assume
FSB400.
I cannot find any evidence there is a Command Rate
setting, unless it is in a later BIOS.

When booted into Windows, you can use www.cpuid.com/cpuz
to monitor the settings used by the BIOS.

******
K8V owners thread - everything you need to know:
http://forums.pcper.com/showthread.php?p=2167438#post2167438

(some trivia - see bottom post for how far from 200MHz
the FSB clock can be pushed...)
http://forums.pcper.com/showthread.php?t=375636&highlight=k8v

(more trivia on adjustments and the early BIOS)
http://www.lostcircuits.com/motherboard/a64_oc/3.shtml

******
Now, some Anandtech reviews, and how well memory
works on S754 boards...

First generation S754 boards. Generally 2 DIMMs at DDR400
http://www.anandtech.com/mb/showdoc.aspx?i=1883

Second generation S754 boards. A mixed bag.
http://www.anandtech.com/mb/showdoc.aspx?i=2063

A third roundup of S754. 3 DIMMs at DDR400.
http://www.anandtech.com/mb/showdoc.aspx?i=2206

What this should tell you, is it is at least possible
that newer BIOS releases will improve performance. There
are three factors at play - controlled impedance design of
the motherboard PCB and stability of onboard power regulation,
setup of memory controller by the BIOS, and improvements
in processor design. The last two are dynamic and can change
with time. For example, the upcoming Venice and San Diego
processors promise better memory interface speed (which
will have to be proven to be believed), so as new steppings
of processors are produced, things can change.

So, while your current BIOS has automatically selected
conservative (AMD approved) settings, there is nothing
preventing you from using the BIOS settings to do better
than the default. Use a memtest86 boot floppy for initial
testing (don't immediately try to boot into Windows),
followed by Prime95 in Windows as the final acceptance test,
will allow you to identify whether your adjustments are
too aggressive or not.

1GB sticks will not behave exactly like 512MB, so your
results will be unique. If you do decide to do some
tuning, report what you find so other Matlab users
can benefit :-)

Paul
 
Paul said:
I cannot find any evidence there is a Command Rate setting, unless it
is in a later BIOS.
Click to expand...
This setting indeed exists. It's likely not in the manual because
original bios did not support it (since this option is only available on
cg and newer stepping A64).
What this should tell you, is it is at least possible that newer BIOS
releases will improve performance. There are three factors at play -
controlled impedance design of the motherboard PCB and stability of
onboard power regulation, setup of memory controller by the BIOS, and
improvements in processor design. The last two are dynamic and can
change with time. For example, the upcoming Venice and San Diego
processors promise better memory interface speed (which will have to
be proven to be believed), so as new steppings of processors are
produced, things can change.
Click to expand...
For socket 754, cg stepping was important (c0 does not exist on socket
939). Since c0 does not support 2T command rate, you can likely pretty
much forget using 3 double-sided dimms at useful speeds. But with cg,
your chances may be a lot better. (I played around with that 2T command
rate option btw on my cg-step A64, you can set it to Enabled, Disabled,
Auto. No matter what, it actually gets always set to 1T... But somewhat
likely if you actually have more than 2 dimms it will indeed get set to
2T. Also, if you play around with memory timings, be prepared for
needing to use the clrtc jumper. This board has some detection when it
no longer boots due to overclocking and resets those parameters in that
case, but in my experience this does not do anything at at all when
overclocking the ram.)

Roland
 
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