DDRAM timings and AMD64?

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View

I have an Asus A8N-SLI Deluxe socket 939 motherboard with
two 1GB sticks of OCZ Platinum enhanced latency DDR500 memory.
I am trying to optimise the memory timings at a FSB of 400MHz.

I am reasonably familiar with the standard DDRAM timing options:

CAS# latency            (Tcl)    2-3T    Use 2.5T
Min RAS# active time    (Trcf)   5-15T   Use 5T
RAS# to CAS# delay      (Twrt)   2-7T    Use 3T
Row precharge time      (Twr)    2-7T    Use 3T

The OCZ web site tells me the settings to use for these.

But there are some new timing options for AMD64 systems, and
I have no idea what the optimum (manufacturer's recommended)
stable settings for these are.

Row cycle time          (Trc)    7-22T
Row refresh cycle time  (Trfc)   9-24T
Read to write time      (Twrt)   1-6T
Write recovery time     (Twr)    2-3T
1T/2T memory timing              1-2T

The last of these options has some help text in the BIOS:

   "Select DRAM commands and addresses will be driven for
    1 clock or 2 clock cycles. 2 clock cycles should only
    be set with unbuffered DIMMs"

Am I right in thinking that someone in the Far East, unfamiliar
with English syntax, has written the logic of that statement
backwards? That it should be:

   "If you have unbuffered DIMMs, you should use 2T, not 1T."

Trial and error with Memtest86+ v1.65 takes at least an hour
before the computer either crashes or detects a lot of memory
errors. It would take me several days to stumble upon the
optimum timings purely by guesswork.

I'd rather find some memory settings that are stable and
reliable, than push the memory to the limit and have a bit
error every half hour.

Does anyone know what the recommended timings are for good
DDR500 memory running at 400MHz FSB?

Re: DDRAM timings and AMD64?

I'm in the same boat with my A8N-E and Patriot DDR500 memory.
Try using the NVIDIA tuning software, might help.

Also people at this site (Forum for A8Ns) might have some good advice.
http://asustech.15.forumer.com /

Quoted text here. Click to load it

Re: DDRAM timings and AMD64?

Yesterday, I wrote:
Quoted text here. Click to load it

I think I've figured it out. At least, I've found settings
that give no errors in a 24 hour Memtest86+ run.

Quoted text here. Click to load it

Based on the minimum and maximum permitted values for
these settings, I'd guess that the optimum values are:

Either, Trc = Trcf + Twrt
    or, Trc = Trcf + Twr

And ordinarily, Trfc = Trc + 2

Quoted text here. Click to load it

The BIOS default value is 5. Setting it to anything
less than 5 gives memory errors in the modulo-20 test:
(00000000 should be ffffffff, or vice versa.)

Quoted text here. Click to load it

If 3T is good enough for DDRAM overclocked to 600MHz
(as it must be, or the maximum permitted value would
be higher), then 2T is perfectly good for DDR400.

Quoted text here. Click to load it

1T must be the setting for registered memory only.
The computer freezes if 1T is used with unbuffered DIMMs.

Re: DDRAM timings and AMD64?

ajmoss_throwaway_account_001@hotmail.co.uk wrote:

Quoted text here. Click to load it

Is this what you're using?


If so then they will run 3-3-3-8 1T at DDR500 with 2.70 volts which is
higher than the default Auto setting. But since you're only running them
at DDR400, they can probably run 2-2-2-5 timings, but you'll have to up
the VDIMM voltage to 2.80v or 2.85v.

I have dual channel OCZ memory that's rated 2-2-2-5 1T but they won't
run at that rate unless I increase the voltage (I'm overclocking the CPU
as well). Many types of OCZ memory are designed to run at higher
voltages, and are fully guaranteed up to 3.0v +/- 5%.

Quoted text here. Click to load it

Are you sure you have your two modules matched and in the proper dual
channel slots (not side-by-side)? I have the Asus A8N-E and it runs two
modules in dual channel at 1T just fine and I know the SLI board is
capable of it too.

It might be a voltage issue. Up the voltage to 2.80v if you haven't
already and try the 1T command rate again. If it still freezes, up the
voltage again to 2.85v and try again.

Re: DDRAM timings and AMD64?

Bill wrote:
Quoted text here. Click to load it

That's the one. I bought the version with the DDR500 timings stored
in the SPD chip, because it was the only OCZ Platinum 2x1GB
memory in stock at the good price I was offered, but I want to run
it at standard DDR400 speeds (not overclocking my CPU).

The SPD chip didn't contain dual settings for DDR400 as well as
DDR500 speeds, so I'm having to look them up on the mfr's web
site, or failing that, guess them.

I happen to know that the recommended timings at DDR400 speeds
for the Gold Enhanced latency DIMMs is 2.5-3-3-5, and the Platinum
EL goes down to 2.5-3-2-5, but when it came to the extra settings
supported bu the AMD64 architecture, I had little choice but to
figure them out by trial and error.

I'm currently running my DIMMs at 2.6 volts, DDR400, 2.5-3-3-5, 2T.
If you say I can get better results by raising the voltage, I might
try that.

Re: DDRAM timings and AMD64?

ajmoss_throwaway_account_001@hotmail.co.uk wrote:

Quoted text here. Click to load it

My OCZ memory is rated to 2-2-2-5 1T but only if the voltage is raised
well above default. Oddly enough the SPD shows it at 2.5-3-3-5 even
though OCZ clearly defines faster.

Quoted text here. Click to load it

Definitely raise the voltage - they're fully guaranteed up to 3.00v so
it won't hurt to try. I'm guessing it should work at 2.70v - 2.80v as
mine work at 2.80v running at DDR400.

However I'm overclocking a bit to DDR416 and they need 2.85v to run at
that rate with 2-2-2-5 1T timings.

Do you have CPUZ to check your results and confirm you're running in
dual channel mode?


Also use the Prime95 "torture test" to ensure the CPU and memory are
100% stable. If it won't run Prime95 without errors overnight, then it's
not truly stable. You can get it here:


The 32-bit version for Windows XP is here:


Site Timeline