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I am looking to upgrade a Desktop currently with 2 sticks of 2GB RAM, by adding a couple of sticks of 1GB RAM. I am unsure what I need to look at to check their compatibility. Both sets of memory run on DDR3, the current 2GB sticks are CH9, while the two I want to add will be CL7. Will these two different types be compatible?

Is there something else I should be looking at to see if the RAM is compatible? Would I be OK to just put both types in the PC and see if at accepts the new RAM or am at risk of damaging something?

Thanks for your help

EDIT:

Current set-up: 2*2GB running at 1600

change to: 2*2GB running at 1600 + 2*1GB running at 1066

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As an aside, typically, the less RAM chips you have, the better access the CPU (motherboard) has access to. So, you'd be better off getting 1 x 4GB ram chip, middle choice would be 2 x 2GB RAM and least performance would be 4 x 1 GB RAM. Of course, it depends on the motherboard. –  Dave Rook Oct 9 '12 at 12:01
    
2x2GB would actually be faster assuming dual channel is used. –  Miles Hayler Oct 9 '12 at 12:23
    
I never heard of CH... CL is CAS Latency en.wikipedia.org/wiki/CAS_latency and it's not the only property for a RAM that counts: en.wikipedia.org/wiki/SDRAM_latency#SDRAM_access & memory clock speed ... Anyway, I tell you one thing, you are light years faster with more RAM than with using the swap file on the disk. Don't worry about clock speeds. You're not running benchmarks on a computer all day. –  Radoo Oct 9 '12 at 14:04
    
Your question is not clear. Please give exact model numbers. You have to explain what CL and CH memory is only because your incorrect usage of terms. –  Ramhound Oct 9 '12 at 14:57
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1 Answer

So long as you set the speeds to the slowest it should be fine (assuming it doesn't automatically!) The most important thing is that the voltage is the same.

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So voltage is determined by DDR3, which is the same on both. I believe that CL7/CH9 is the speed, is this correct? How would I set the speed? –  Pezzzz Oct 9 '12 at 11:35
    
The speed is set in the BIOS and the speed and timings would be printed on a sticker the RAM itself. If you can find a model number for each type of RAM I can help that way. –  Miles Hayler Oct 9 '12 at 12:24
    
I have added the speeds to the question. taking the advice of as few chips as possible; it appears to me that just keeping the faster bigger chips would be better than adding two extra slower chips. Does it look the same to you? –  Pezzzz Oct 9 '12 at 13:08
    
If you were to add the extra 2 sticks, you would have to have them all running at 1066. Some programs will run quicker with more RAM, and some will run quicker with faster RAM. I assume you're running a 64bit version of Windows 7? –  Miles Hayler Oct 9 '12 at 13:50
    
Yes I will be on windows 7. Currently I use the 2*1GB sticks in XP and have some memory issues with large Excel workbooks. I am upgrading to a new system with the 2*2GB sticks on Win 7 and am wondering if it is worth migrating the old RAM across with me. –  Pezzzz Oct 9 '12 at 14:20
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