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Performance Issue if all 3 dimm slots Populated


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I have an ASUS K8V-X which has 3 DIMM sockets. I've been using 2 sticks of 512 DDR400 PC3200 memory--and everything benchmarks accordingly.


The Problem:

I bought a 1gig DIMM to up my total RAM to 2gig


So now it's:

DIMM1: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)

DIMM2: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)

DIMM3: Corsair VS1GB400C3 1 GB PC3200 DDR SDRAM (3.0-3-3-8 @ 200 MHz)


Everything benches at PC1600 level and the computer is in fact slow as Cold Molasses.


I expected to take a slight hit because of the 3.0 Latency of that 1 Gig DIMM but these 3 DIMS combined are benchmarking at slow PC1600 level.


Just the 1 Gig by itself or just the 2 512 sticks by themselve--bench in the high PC3200 range--as I would expect.


Is this a problem with mixing the 1gig & 512mg DIMMS together on this particular mobo?


Edited to add:

Sorry RamGuy --this might not be the best subsection for this post...It's here now:-)

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Actually, it's a problem with most Socket 754 motherboards as well. Filling all three memory slots with double-rank modules on such motherboards will drop your memory speed all the way down to 100MHz (DDR200/PC1600) even if all three modules match each other exactly.
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True Wired, but the difference in specs apart from the size is a minor difference in latency that would have minal impact-wost case it drops all three DIMMs to a 3 latency.


There's also more to this:

I've been running 3 512 sticks---also maxing out the memory controller but in that case even though one of the 512 sticks is PC2700** the performance hit as it drags all 3 slots down to it's speed is NOTHING Like when i've got all PC3200 dimms but one's twice the size of the other 2.



It just seems to me there's more to this huge Mem Bus hit than the obvious and I do hope I more feedback here.


Edited to Add

Well RJLeong65's you answered while I was typing but that's exactly the kind of feedback I'm looking for and you're not the first to suggest that.


**actually that PC2700 may be what keeps that config from dropping the mem bus down to 100mhz. Othe feedback I've seen today suggests the ONLY way to have 3 DIMMS and NOT drop the bus speed is if the 3rd DIMM is

Single side. It's my understanding that ALL 1G DIMMs are double-ranked but that PC2700 may be single sided...I'll have to look specs up on the internet.


Doesn't seem like these 3 DIMM slot mobo were very well concieved in terms of RAM.

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What about this config RamGuy:

3 completely identical DIMMS

DIMM1: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)

DIMM2: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)

DIMM2: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)


Could I expect this to perform at DDR400 speed?

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"And all 512 Meg and larger modules are double sided."

Good info and if it comes from Ram Guy you can achive it and store it as a RAM-Fact.


I have been running TWO corsair VS512MB400 512 MB--DDR400 DIMMS in this mobo for 8 months now and it's been very stable at a full 200Mhz RAM BUS.


Actually I'm in a very slight overclock experiement now with my corsair RAM.


Current config is:

DIMM1: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)

DIMM2: Corsair VS512MB400 512 MB PC3200 DDR SDRAM (2.5-3-3-8 @ 200 MHz)

DIMM3: Corsair XMS Extreme Memory 512MB PC2700 DDR 333MHz (2.5-3-3-7 @ 166 MHz)


So when the computer booted normally I was looking at RAM Bus of about 162Mhz--already BELOW the SPD spec for the slowest DIMM in that config.

Now I'm turning up the CPU FSB --which started at 200Mhz. Now @ an FSB of 211Mhz the CPU corespeed is 2532Mhz and the RAM BUs is 169Mhz--'bout DDR338.


CPU temps are still in the 30's and if I have time I'll crank the FSB up some more see where the system starts to become unstable.


I'm not an overclocker at all but in my normal experience--if I'd started out at a RAM BUS of 200Mhz and THEN cranked up the FSB BUS I'd already being seeing RAM Instabilities now...So...just out of curiosity.....I'm assuming that Corsair XMS Extreme DIMM has a little more room to go over it's specs than than a normal corsair "DIMM" would--or is the "extreme" more in terms of pushing the latency values?


Edited to add

Looks like Stabilty begins to depart above FSB 217

At that FSB I've got:

CPU Core 2591

RAM BUS 172.8Mhz

effect RAM speed 'bout DDR346


I was hoping I could push the FSB a bit higher as that's still petty much below DDR400--but I doubt I'll start playing with Voltages and other overclock tweaks :-)

Still if you look at the XP perforance boost by incresing RAM from 1G to 1.5Gig --at least as it plays out in my world, that's probably worth it even though it's slower than my best available 1Gig DDR400 configuration. If it's really stable at FSB 216Mhz-- I might leave it like this for now.

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Interesting Ram Guy---It did NOT appear that it was the Corsair memory crapping out on me above 217Mhz FSB.


In my case it appeared to be related to the IDE Data exchange---and I have a Promise/Maxtor PCI IDE extender card--to give me 8 IDE devices and a couple of SATA Drives AND an external Fireware AND an External USB HDD to boot**! So my rig is NOT exactly an overclocker's dream under any circumstance.


**Yup pushing 2 terabytes now. And Still I seem to run out of secondary!!


Good to know that if I wasted time trying to sort out the IDE issue--I'd probably be hitting an Graphic Card issue anyway...:p:

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