OT: Memory expert please :-)

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RJK

I just bought 2x512 ddr400/pc2300 Corsair XMS 3200LL modules, and after
doing quite a bit
of Googling,
I am no further forward in determing the "best" settings in bios, and
indeed, my bios has slightly ambiguous labels which are hard to match up
with,
tRCD, tRP and tRAS etc.
http://www.techpowerup.com/articles/overclocking/64
i.e Which one is which ?

If I set bios to use SPD, Lavalys Everest "motherboard" ICH5 reports :-
Memory Timings:
CAS Latency (CL) 2T
RAS To CAS Delay (tRCD) 2T
RAS Precharge (tRP) 2T
RAS Active Time (tRAS) 5T
???

I've just set manually in bios:- (Below is how the bios memory setting
options appear on screen btw),
DRAM CAS# Latency 2.5
DRAM RAS# Precharge 3
DRAM RAS# to CAS# Delay 3
DRAM Precharge Delay 5
DRAM Burst Length 4
....and CPUZ reflects these settings accurately, ...(dunno what Lavalys
Everest is doing ?!)
anyhooo...
....completely confused, after reading lots about setting CAS to 2 can not be
as "good" as setting it to 2.5 ???

....any advice much appreciated,

TIA

regards, Richard
 
RJK said:
I just bought 2x512 ddr400/pc2300 Corsair XMS 3200LL modules, and after
doing quite a bit
of Googling,
I am no further forward in determing the "best" settings in bios, and
indeed, my bios has slightly ambiguous labels which are hard to match up
with,
tRCD, tRP and tRAS etc.
http://www.techpowerup.com/articles/overclocking/64
i.e Which one is which ?

If I set bios to use SPD, Lavalys Everest "motherboard" ICH5 reports :-
Memory Timings:
CAS Latency (CL) 2T
RAS To CAS Delay (tRCD) 2T
RAS Precharge (tRP) 2T
RAS Active Time (tRAS) 5T
???

I've just set manually in bios:- (Below is how the bios memory setting
options appear on screen btw),
DRAM CAS# Latency 2.5
DRAM RAS# Precharge 3
DRAM RAS# to CAS# Delay 3
DRAM Precharge Delay 5
DRAM Burst Length 4
...and CPUZ reflects these settings accurately, ...(dunno what Lavalys
Everest is doing ?!)
anyhooo...
...completely confused, after reading lots about setting CAS to 2 can not be
as "good" as setting it to 2.5 ???

...any advice much appreciated,

TIA

regards, Richard
Click to expand...

CAS affects the latency. Lower CAS is better. 2 is better than 2.5 .

Corsair products tend to have datasheets. If you look hard enough,
you can find the exact one for your RAM. I'm not sure whether this
is yours or not (need the full part number).

http://www.corsairmicro.com/_datasheets/twinx1024-3200ll.pdf

CPUZ from cpuid.com, displays two things. In the "SPD" tab, you
can see the values recorded in the SPD chip on the DIMM. That
may or may not reflect what the memory is actually capable of.
And will help you understand what the BIOS will do, when the
BIOS is set to use SPD. You compare the CPUZ SPD values to the
datasheet values, to see whether the SPD actually contains the
correct data. On some RAM, slower settings are used in the SPD,
to guarantee that the motherboard will POST - then the user
sets things manually, to the datasheet values.

The CPUZ "Memory" tab, shows the current choices for Tcl, Trcd, Trp, Tras.
So you can see what settings actually resulted.

When you see 2,3,2,5 in the datasheet, the order is "CAS Latency, tRCD, tRP, tRAS",
the same as in CPUZ.

I hope that answers your question.

Paul
 
Huge thanks,

....eventually noticed, in CPUZ that my i865PE based mobo/D935cpu | bios
"Auto" option was stubbornly setting FSB at 133mhz !!!,
....have now forced that to 200mhz in bios and CPUZ now reports fsb at
199.7mhz,
and fsb:dram ratio at 1:1 ...where it should have been - instead of 4:3 or
3:2 ...whatever it was,
etc, ....what fun ! ...in a minute or two I shall have a blue screen -
....I can feel it coming my way !

....do you think that I have matched up the labels correctly ? :-
i.e. am attempting to match CPUZ SPD info with my bios options,
...as below:-
tCL = DRAM CAS# Latency 2.0
tRP = DRAM RAS# Precharge 2
tRCD = DRAM RAS# to CAS# Delay 3
tRAS = DRAM Precharge Delay 6

? DRAM Burst Length 4
http://www.rambus.com/us/patents/innovations/detail/variable_burst.html
....now I have to choose between 4 and 8 !!!

regards, Richard
 
....though, I must say that, I've always been an "anti-overclocker," so I am
therefore a bit loath to raise my head above parapit in a "OC forum" !
....it's just that I've always been aware that higher performance memory was
available, and I have kept my "eye" on discussions across the years, i.e.
there appeared to be not a lot to be gained by paying a fortune for "higher
performance" memory modules.
However, seeing as my "old" Conroe i865pe has "older" ddr slots, with 2x512
Crucial CL3 pc3200 modules in it, and seeing as people are flogging on ebay,
their Geil and Corsair ...and Infineon CL2 ddr400 modules for a fraction of
what they cost new, I thought I'd buy a couple and see if I could notice an
improvement in performance.

....which was all a worthwhile, if only because whilst attempting to find the
correct manual settings for this "new" memory, I discovered, with the help
of CPUZ, and Paul (on this thread), that one of my stupid bios options was
causing cpu fsb to be set at 133mhz. How it ended up on "Auto" on the CPU
settings screen in bios, and how long it's been like that - I don't know.
i.e. I've kept an eye on those settings several times across the past year
or two, and to the best of my memory had never selected "Auto" !

....anyhoo, ...I "think" that I have finally selected the correct memory
timings !

regards, Richard
 
RJK said:
Huge thanks,

...eventually noticed, in CPUZ that my i865PE based mobo/D935cpu | bios
"Auto" option was stubbornly setting FSB at 133mhz !!!,
...have now forced that to 200mhz in bios and CPUZ now reports fsb at
199.7mhz,
and fsb:dram ratio at 1:1 ...where it should have been - instead of 4:3 or
3:2 ...whatever it was,
etc, ....what fun ! ...in a minute or two I shall have a blue screen -
...I can feel it coming my way !

...do you think that I have matched up the labels correctly ? :-
i.e. am attempting to match CPUZ SPD info with my bios options,
..as below:-
tCL = DRAM CAS# Latency 2.0
tRP = DRAM RAS# Precharge 2
tRCD = DRAM RAS# to CAS# Delay 3
tRAS = DRAM Precharge Delay 6

? DRAM Burst Length 4
http://www.rambus.com/us/patents/innovations/detail/variable_burst.html
...now I have to choose between 4 and 8 !!!

regards, Richard
Click to expand...

The numbers as presented, are consistent with a 2-3-2-6 RAM. The order of
appearance in the BIOS list, is not the same as the "standard" order
shown in advertisements and documentation. As long as you remember your
2-3-2-6 is Tcl, Trcd, Trp, Tras, you should be OK. So when looking
at the BIOS screen, you have to remember that they didn't put the
parameters in the standard order.

The "DRAM Burst Length" can be left at [Auto], as it makes no sense to
program it. As far as I know, the value "4" is used for dual channel
memory configurations. If the BIOS detects a dual channel configuration,
the BIOS should use the value 4. If the BIOS detects a single channel
memory configuration, then it should use the value of 8. I think the
idea is, the total amount of data taken from the memory ("4" x 16 bytes
or "8" x 8 bytes), should match the cache line size of the processor.
I don't play with that setting, and leave it at Auto, because the
BIOS is more clever than I am :-)

Paul
 
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