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Adding more memory of different revision-a no go!


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After some initial problems, my machine (Intel 805, 2x512 mb xms2-6400 cl5, rev 1.8 on Asus p5dh deluxe) has been running fine for a year. Recently. I decided to upgrade with a new cpu (c2duo 6750) and som more memory to get the maximum of 3 gb that is usable in Win xp 32bit. Naturallly I ordered memory of the same brand, type, and timings (2x1024 mb xms2-6400 cl5, rev 5.1) in order to avoid any compatibility issues - or so I thought.....


After installing the new memory the system would not even post. After switching places of the 512 and 1024 parts it booted but soon hung in windows. I tried upping the Vmem (up to 2.2V), Vmch and Vfsb, lowering timings, running it at lower speed (667 mhz), but I could not get it stable and had lots of errors in memtest. I actually got the best results when I lowered the timings to 4 4 4 12, which was more stable than 5 5 5 12. Removing either the 512 or the 1024 parts made the machine perfectly stable and it ran memtest without any problems.


I then took the 512 mb sticks to work where I have a similar computer (C2duo 6600, Gigbyte p35ds4 with 2x1024 mb xms2-6400 cl5, rev 5.1) and the same problems occurred there. Using only the 512 mb parts I ran memtest for 3 hrs without any errors.


To test if it was the mobo that couldn't run with all four banks populated, I took home my two sticks from work and added to my own (which are of the same revision). At 2.0V vmem I still had some errors in memtest, but at 2.1V it ran over night at 4 4 4 12 withour any errors. So, the mobo can run with all four banks populated, but not with the older revisions of the memory. The 512 mb parts work fine by themself, but does not work with newer revisions.


In my world that means that they do not function as they should, but the place I bought them from does not agree and will not take them back. I realize that compatibility issues are everywhere in the computer part business, but I did all I could to avoid such problems in buying the same type of memory. If one cannot upgrade a system with more memory after a while, that is something that should I should be warned about both when I bought the first sticks, and most definitely when I bought the second pair.



Some hardware info

c2duo 6750 with Tuniq tower

Asus p5dh deluxe

GK PCIe X1950ProSCS3 256MB

1 SATA hd

1 Samsung dvd

Corsair 620W psu

Aerocool extreme engine 3t

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Is this dual channel memory? Even though the memory is the same brand, timings, etc but because two are 512MB and the other two are 1GB sticks they will not run together. Think of it as though they were on a balance. The 512MB pair on one side and the 1GB pair sticks on the other. It would create an unbalance on the MB bewteen the ram slots. Does that make sense?

I think that is your problem if I understand correctly.

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I understand what you mean, but that isn't how they are paired up. First of all both the 2x512mb and the 2x1024 are matched memory pairs, so they can run in dual channel mode. Secondly, in the mobo they are paired up with each other so that the 512 mb sticks runs in one memory channel (orange slots) and the 1024 in the other (black); 512, 1024, 512, 1024. This is the way they are supposed to be in order to run them in dual channel.
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I now use a c2duo 6750, but before I installed it I tried running the 2x512 + the 2x1024 with the 805D, and then I also lowered the speed of the memory and increased the Vmem Vmch (memoryhub), but I don't remember exactly the things I tried then. After my cpu-upgrade I have tried lowering the memory speed and different vmem (from 1.95 to 2.2V) and increasing the Vmch (memoryhub) as well as the Vfsb, also tried different timings as well as using auto. I will try once more and lower the memory speed as much as I can and see if I can get them to run reliably at any speed.


However, the computer worked just fine with the other memory sticks that were of the same revision with only a slight increase of Vmch, vmem 2.1V and 4 4 4 12 timings, both around 667 mhz and 800 mhz (overclocking the cpu).

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