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Different size ram sticks

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January 24, 2009 10:58:24 PM

Hi I have an ASUS P5KC mobo and it currently has two 1gb sticks of G.SKILL ddr2 8500, 1066MHz cl 5-5-5-15 dual channel ram. I'm thinking about two sticks of 2gb ram of exactly (same brand timings, everything) the same ram. I'm just wondering if this will work properly with my mobo, and still in dual channel mode? Or will I need to just leave the two 1gb stick out?

Thanks to anyone who can help.

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January 27, 2009 6:01:53 AM

If you notice on your mobo the memory slots are colored differently. As long as you put the 2x2gb sticks into the same color slots they will be duel channeled and work with your existing memory despite that they are smaller sized units. For example you want want your 1gb sticks in YELLOW slots and your 2gb sticks in BLACK slots.
January 27, 2009 6:31:57 AM

jfurterer said:
If you notice on your mobo the memory slots are colored differently. As long as you put the 2x2gb sticks into the same color slots they will be duel channeled and work with your existing memory despite that they are smaller sized units. For example you want want your 1gb sticks in YELLOW slots and your 2gb sticks in BLACK slots.


Thanks very much!
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January 29, 2009 12:09:04 AM

Just received them and have put them in, it shows as 6.00 GB ram but for some reason it has downclocked it from 1066 MHz that it was when I had just the 2 * 1GB sticks in to all four sticks now being run at 800 MHz. Why has this happend and how do I fix it? As a note I'm defiantly sure that they both support 1066 MHz.
January 29, 2009 12:17:47 AM

You will most likely need to adjust the timings in the BIOS. This can be tricky with different sized models, but most likely will be possible.
January 29, 2009 12:43:59 AM

scrumhalf said:
You will most likely need to adjust the timings in the BIOS. This can be tricky with different sized models, but most likely will be possible.


I tried setting it to 1066 MHz in bios but it hasn't done anything =\
January 29, 2009 12:53:27 AM

If you take the new ram out does your system report DDR2-1066 for the original? I'm going out on a limb here but it may be that the timings are different. Smaller quantity modules usually have tighter timings. If your the original ram is in fact recognized at 1066 check the timings. Then install the new ram and adjust it's timings to that of the original see if that works.

I've run 2x512mb and 2x1gb ddr2-667 ram dual channeled with no problems. You should be able to support two different sized ddr2-1066 modules. Another thing to look into is whether or not the new ram is has a stock speed of 800 but is sold as OCable to 1066. In that case you'll need to lower your orginal ram to 800 and over clock the whole bus to 1066.
January 29, 2009 1:04:29 AM

CPU-Z reports both the 1GB stick and the 2GB stick as having the same timing. It also displays the FSB:D RAM as 2:3 where as it was 1:1 before. The only thing that is different as far as I can tell, by looking at CPU-Z is the volts, which are at 2.35 V for the 1 GB stick and 2.1 V for the 2 GB stick. I will take out the new stuff now and see if it reports it as 1066 MHz like you suggested.

Edit: Just removed the new memory and left the old in there like you suggested, this is now also at 800 MHz instead of 1066 =\ I will try just the new memory now.

Edit 2: Tried the same thing as above but with only the new memory in. This is running at 800 MHz also :??: 
January 29, 2009 11:45:11 AM

Most likely you will have to set the timings by hand then. One other question i'd ask is, are you overclocking a great deal? if not do you really need to run at 1066mhz?
January 29, 2009 3:10:27 PM

It sounds like your new ram clocked the whole ram bus down to 800. The good news is if everything is at 800 you can easily over clock it back up to 1066. I'm guessing that if your ratio is 2:3 that your reference clock has been underclocked to 266mhz. I don't over clock allot however it sounds like you'll need to push your reference clock up to 533mhz. That's allot. You may however be able to change your CPU multiplier but most times the CPU multiplier is locked in which case you'll only be able to up the reference clock. I'd increase it by small intervals (20mhz) checking the RAM speed as you go and how stable the system is untill you reach a ram speed of 1066 or the system becomes unstable. You may need to increase the voltage to your north bridge chip set as well as your RAM.
!