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Best Memory (DDR2 SDRAM) Configuration

Posted on 2008-10-16
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Last Modified: 2013-11-10
Hi!

In a motherboard (ASUS P5QL-E) with 4 dimm slots (max 16GB), which would be the best memory configuration?

I am currently not able to get 1066MHz memory, so will settle for 800MHz.

I need a total of 4GB as I'll be using Win XP 32-bit.

The problem is I already have 2GB (2x 1GB Corsair matched memory pair)
http://www.corsair.com/_datasheets/CM2X1024-6400.pdf

Should I use these and add 2x 1GB Kingston RAM modules or should I keep the Corsair for other use and get 4x 1GB Kingston RAM modules?
http://www.valueram.com/datasheets/KVR800D2N6_1G.pdf
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Question by:Julian Matz
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by:chrisat
chrisat earned 75 total points
ID: 22737566
Your best bet would be to go with 2 x 4GB modules, but with the options you've listed I would go with the 4 x 1GB modules..  I wouldn't recommend mixing different types of memory especially from different vendors, but YMMV.  
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by:Julian Matz
ID: 22737584
You mean 2x 2GB ?

Another option I suppose would be to use the 2GB Corsair until the other RAM comes back in stock and I place my next bulk order ...
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by:PUNKY
PUNKY earned 75 total points
ID: 22737586
Add 2 x 1GB + what you already have. The board you have does not restrict memory size across two channel, you can install different memory size either dual or single function same time (it is nice feature from Asus), so you even buy a single 2G stick to install.
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by:Julian Matz
ID: 22737596
PUNKY, do you mean I can still utilize dual-channel as long as I have 2 matching pairs - even if the the 2 pairs are different?
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by:PUNKY
ID: 22737620
Careful with term of dual channel:
http://www.crucial.com/kb/answer.aspx?qid=3751
Yes, you can use 2 differ pairs on this board.
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by:michote
ID: 22737632
okey the problem here is that windows xp (32bits) can not access 4gb. It only can acces like 3.2 o 2.6 gbs depending on your config
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by:PUNKY
ID: 22737633
Also, check board manual, the information is all there. I have same board with you (several of them), and I dont see any differ performance either mixed or matched memory (all running XP 32 bits) ... and my users are free to configure memory their own way ...
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by:Julian Matz
ID: 22737682
I know about the 32-bit restrictions but as I understand it, having 4GB installed is still better than having 3GB installed. I'm not an expert on this but according to Microsoft the limit in Win XP 32-bit is 4GB. As I was told, 1GB would be reserved for system devices, 1GB utilized by Windows and 2GB for applications.

I presume the differences between CL4 and CL5 memory would not be noticeable?
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by:PUNKY
ID: 22737701
*** differences between CL4 and CL5 memory would not be noticeable?***
If you do overclocking you might see differences but I never try so.
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by:Julian Matz
ID: 22737786
Thanks for all the help!

PUNKY, one quick (off-topic) question, since you also seem to use ASUS boards: are all of ASUS' newer models Vista-ready? I used to see it mentioned under the specs but don't anymore. I presume they would be...
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by:PUNKY
PUNKY earned 75 total points
ID: 22737811
The term Vista Ready is no longer used since most modern motherboard, not only Asus, are for Vista and they are not ad it.
I dont own them, in fact, my company bought new motherboards (most of them are just coming out market) for application testings and other new hardware to add on them.
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by:_
ID: 22737895
just a side note:
if you are going to use ram with different CAS timings, I would either put the slowest pair in channel 1 so the bios will use that SDP info, or set the timings manually, to keep the faster pair from trying to run the slower ones at a rating they will not like.
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garycase earned 350 total points
ID: 22738005
I would not use your existing modules -- I'd get a pair of 2GB modules.   On a motherboard that uses unbuffered memory, it's much better to only install 2 modules ... especially if they're double-sided modules.   The address and data bus loading caused by 4 modules [64 loads if they're double-sided] causes significant signal deterioration and a much less reliable memory subsystem.   Many crashes blamed on Windows are actually the result of memory errors on systems with 4 installed modules and no error detection/correction (ECC) capability.

Just to correct a comment above:  If you have multiple modules installed with different timings, it doesn't matter which slot the slowest pair is installed in ==> the system will use the SPD info from the slowest module regardless.
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by:garycase
garycase earned 350 total points
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... a couple other comments ...

r.e. "... 1GB would be reserved for system devices, 1GB utilized by Windows and 2GB for applications ..." ==> No, but that's a close approximation.   There's no specific amount reserved for system devices ==> they are assigned as needed, starting from the top of the 4GB address space.   I've seen as little as 2.5GB left over after these assignments; and as much as 3.75GB (rare).   On the system I'm typing this on I have 3.5GB available.    Indiivdual processes are limited to 2GB ... but that doesn't mean only 2GB is available for applications, as it's common to have multiple processes running, and EACH can be using 2GB.   Nor does Windows automatically use 1GB ... it will use what it needs, but can and does use additional memory to map into the virtual address space of the running processes as needed.

"... I presume the differences between CL4 and CL5 memory would not be noticeable? " ==>  Correct.   The difference would easily show in any benchmarks you might run;  but will not be noticeable in the performance of the system in most applications.   1 clock cycle at 800MHz is 1.25 ns => so the CAS latency difference is adding 1.25ns per memory access for all cache misses (accesses within the CPU cache have zero latency).   You'd only notice this kind of difference in benchmarks or in extremely memory bounded applications (e.g. a memory test).
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by:_
ID: 22738070
>> the system will use the SPD info from the slowest module regardless.

Sweet. The bioses got smarter since the last time I tried that.   : )
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by:Julian Matz
ID: 22742022
Thanks for all the help. One last question:

Can I use any DDR2 SDRAM 240-pin non-ECC RAM in this board or is it advisable to stick with memory suggested by the RAM manufacturer's memory configurators?

I ask this because I've been looking at the Kingston ValueRam and Kingston HyperX configurators and none of the modules seem to be in stock. However, when I do a manual search on my suppliers interface I get the following option:

KVR800D2N5/2G - Memory/2GB 800MHz DDR2 Non-ECC CL5 DIMM
KVR800D2N5K2/4G - Memory/4GB 800MHz DDR2 Non-ECC CL5 DIMM (Kit of 2)

But when I check the KingstonVR configurator these aren't listed - all the 800MHz modules listed are CL6, which is the only difference I can see.

Also with the HyperX memory, I found this one:

Memory/4GB 1066MHz DDR2 Non-ECC CL7 (7-7-7-20) DIMM (Kit of 2)

Which is not listed on the HyperX configurator (all the modules listed are 800MHz).
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by:Julian Matz
ID: 22742034
KHX8500AD2K2/4G - Memory/4GB 1066MHz DDR2 Non-ECC CL7 (7-7-7-20) DIMM (Kit of 2)
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by:garycase
ID: 22742985
Either of the above should work fine.  The only possible "glitch" is that the 2.0v module may require an adjustment in the BIOS to set the higher voltage (the DDR2 standard is 1.8v) ... but most boards will automatically set this.
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by:Julian Matz
ID: 22743618
Are they not both 1.8v ? I thought I saw it in their spec sheets ...
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by:garycase
ID: 22743889
The last one (the 1066Mhz) is a 2.0v module.
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by:Julian Matz
ID: 22743940
Ok, I just saw it on the product summary page. But on the spec sheet it says +1.8V (+/- .1V)
Timing Reference: 6-6-6-18 at +1.8V / 7-7-7-20 at +1.85 to +2.0V

http://www.valueram.com/datasheets/KHX8500AD2K2_4G.pdf
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by:Julian Matz
ID: 22743946
By the way: which one of thos would you recommend. I presume the HyperX one?
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by:garycase
garycase earned 350 total points
ID: 22745117
Ahh .. it runs fine at 1.8v at 800MHz, but needs 2.0v to run at 1066 => so it will work just fine [It will likely default to the 800MHz speed based on the SPD timing info].   I think either of the modules would be fine ... the Hyper-X would let you experiment with the higher speed setting, so it's a good choice.


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by:Julian Matz
ID: 22859102
Thanks for all the help and info! I got 3.25 GB of useable memory so am happy enough. The Intel E8500 is running well by the way, garycase, so thanks again for that too :)
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