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Mixed RAM troubles

  • Memory
Last response: in Memory
February 15, 2007 1:18:38 PM

I just bought a pair of Corsair XMS2 DDR2-675 (2x512) to go with my pair of Patriot DDR2 667 (2x512).

When I have both pairs in in dual-channel, the computer refuses to boot, when I mix the sticks around, I can get it to boot (bad stability), but under memtest I have massive memory error. I checked every stick individually and none have errors, and then ran each pair in dual-channel in memtest and got no errors so I'm 99% sure the ram isn't at fault. I raised the ddr voltage to 1.9 because thats the rated voltage for the Corsair so that's also not a factor.

Abit AL8-V
P4 631 (3.0ghz)
580watt Raidmax aurora PSU
2 random IDE HDD
XP Home SP2

More about : mixed ram troubles

February 15, 2007 3:31:26 PM

I thought that ram speeds had to be the same?
February 15, 2007 3:40:54 PM

well, I have them set to same speed in BIOS. I can also run one of the Patriot sticks with the two corsairs, but not both. Updated Bios to newest version as well.
February 15, 2007 4:07:41 PM

Well, you found the old memory conundrum - different brands may work together - and they may not. At least your box will boot with different sticks, I've had machines that wouldn't even boot with mis-matched ram. Besides ddr2 is still more or less in the developmental stage compared to the fully stabilized ddr platform that's been optimized over the last 4+ years.
February 15, 2007 4:14:16 PM

Your ram is fighting with itself, kind of a civil war going on. The spec voltages are different, the timings may not be the same, and the speeds are slightly different (675 vs 667). This is why there is such great importance for matching the ram, if not in company, at least in basic specs. Apparently each companies pair works great, but just not with each other. Now you have to make a choice, either buy another pair that matches one or the other existing pair, or just pull a pair and run on one 2 x 512 mb pair for the time being.
February 15, 2007 4:22:00 PM

Well, timings are the same (if not, i've forced them to be) voltages are definitely not the same, but they boot with mixed (as long as both pairs arent in dual-channel)

I tried something just randomly..Lowered the BIOS speed of the ram down to DDR2-533 and I can boot no problem with both sticks in, no instability so far..

Iunno..I jsut figured since they're both technically PC-5300/5400 that it wouldn't make a difference if I matched the pair..oh well. I think I'll stick with leaving it at 533 for now till I figure out a better plan
February 15, 2007 4:44:22 PM

I tried something just randomly..Lowered the BIOS speed of the ram down to DDR2-533 and I can boot no problem with both sticks in, no instability so far..

Iunno..I jsut figured since they're both technically PC-5300/5400 that it wouldn't make a difference if I matched the pair..oh well. I think I'll stick with leaving it at 533 for now till I figure out a better plan

Dropping both pairs to a lower speed now has them running equally, so that works out. Good if this works and glad for you. When you have more time and money, probably mainly money, it would be good to get a pair of 1 gig sticks so you have a total of 2 gig and they work properly together.
February 15, 2007 4:56:48 PM

What timings do you force onto the modules?
February 15, 2007 4:59:47 PM


and I DO have two gigs of ram, now that the speeds are the same. I ran some benchmarks and everything seems to be the same as when I had the speeds at 667, so I think i'll stick with this :o 
February 15, 2007 5:35:13 PM

Hello fellow ABit-guy,
I just checked your stuff out - Intel 945P chipset, P4 3GHz @ 200FSB (800QDR).
So your mobo runs 200 FSB coreclock and your CPU has a multiplier of 15x... heheh, your mobo supports the faster 266FSB (but probably no guarantee the CPU could go 4GHz 8O )
Anyway: back to your memory problems, LoL
So you have an asymmetric 3:5 ratio (FSB:memory) providing more memory bandwidth than your CPU needs - let me explain...
The memory speed needed to be faster than CPU because CPU FSB is quad-pumped, and memory only DDR.
But when dual-channel 128bit memory was introduced, things changed!
Now 200FSB x 4 = 800MHz
And 200 memory x 2 = only 400MHz (half the CPU bandwidth)
But dual-channel DDR doubles that again! So dual-channel DDR400 matches 800FSB precisely.
Now, your RAM in those early Socket775 mobos could possibly be installed by many as only single-channel, so 667MHz is closer to 800MHz (at least better than 400MHz which is obviously only half, right?)
The bottom line is, dual-channel DDR2-667 far exceeds your 800FSB CPU bandwidth. It even exceeds the newer Core2 CPU bandwidth!
So you, trying to make 4 sticks play nice together, don't need to push the memory speed in MHz.
In a perfect world you would increase your CPU FSB to 266, and decrease your memory clock to 266 (533DDR) and everything would match up precisely :) 
Anyway: in your BIOS setup, on the uGuru Utility setup page they call 'OC Guru', is where you set these ratios.
You know where this is if you have adjusted your memory voltage :lol:  heheh...
So the DRAM Frequency (CPU:D RAM) adjustment there, is what I'm talking about! It needs to be 1:1 (not 3:5).
I realize your memory would therefore come up as DDR2-400 but that is unimportant as I've tried to explain (above).
If you wish to run faster DDR2-533 speed you should increase CPU FSB coreclock to 266MHz. See?
Notice also the 'N/B Strap CPU As' setting there, where you can manually select your hardware strap to MCH (memory controller hub).
I would increase the memory voltage to ~2.0V and reduce the memory speed in MHz.
There are 3 ratios from which to choose:
1:1 = 400DDR
3:4 = 533DDR
3:5 = 667DDR
Start with the slowest synchronous (1:1) memory speed, and confirm it is solid/stable.
2.0V memory and easy memory timings for now...
Hey there is probably some confusion if your mobo is trying to read SPD info!
Run each memory brand individually and read SPD info using CPU-Z.
Select timings that each pair of sticks can agree on, and manually specify these if req'd.
CPU-Z will tell you both the SPD info and also exactly what your mobo is giving you - so you can tell if, say, your one pair of RAM will do it but the other will not...
Also, there is a timing setting 1T or 2T (2T is good for running 4 x 512MB sticks) and the extra tick is required for stability.
Anyway, good luck to you and I hope you don't dismiss my ideas as being loopy - I'm just applying modern Conroe (Core2) memory tuning techniques to your 945P rig!
Personally I would see if your rig will POST @ 266FSB coreclock (4GHz CPU). Good cooling and high CPU voltage would be req'd for this 33% OC attempt...
But hopefully reduced memory speed will fix you right up (and should not affect your performance). Let us know what you discover,
February 15, 2007 5:35:36 PM

I realize that you do now have 2 gig of ram. Perhaps I should have been more specific in saying 2 gig of matched ram. However, if everything is working fine for you and you're happy, then well and good and nothing needs to be changed.
February 15, 2007 5:54:41 PM

The_OGS, I'll definitely try that tonight and see if I can get the 266. I'm not too worried about the cooling, because I have the cedar mill core (a little cooler than the prescott) and a Thermaltake Big Typhoon, so my cpu is usually around 19-24c.

I'll post later tonight with my results :D 

Thanks for feedback everyone!
February 15, 2007 11:08:00 PM

Rather than the two manufacturers' modules not being compatible with each other, a more likely explanation IMHO is that the MB cannot support all 4 slots full at the highest speed. Similarly, many new MB support 8GB RAM max (at DDR2-667 and slower speeds), but only 4GB RAM max at DDR2-800 speed.
February 16, 2007 3:22:33 AM

Hmm...having troubles getting above 230..any suggestion on the process for increments on vcore/bus speeds?