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Mixing latency of memory

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September 17, 2010 10:04:15 PM

I'm rebuilding a system for a friend and I'm replacing the MB, CPU, PSU and OS and adding 2 GB of DDR2 RAM. I didn't check quite close enough on the RAM modules and now find that I've ordered a 2 GB Dual Channel Kit that is identical to the existing RAM except that the latency is different. Existing RAM has 4-4-4-12 latency and the new RAM is 5-5-5-18 latency.

Both sets are CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel and the only other difference is the voltage. Existing RAM lists voltage as 2.1V and the new set lists voltage as 1.9V.

I've checked this and other forums about this and it seems that it will be OK but thought I'd post here to get confirmation and some more detailed info as to what the results of mixing latency might be.

New system will consist of:
GIGABYTE GA-MA785GM-US2H AM3/AM2+/AM2 AMD 785G HDMI Micro ATX AMD Motherboard
AMD Athlon II X2 250 Regor 3.0 GHz 2x1 MB L2 Cache Socket AM3 65W Dual-Core
Rosewill Green Series RG430-S12 430W Continuous @40°C, 80 PLUS Certified, Single 12V Rail, Active PFC
Windows 7 Home Premium 64-bit

The normal vendor I use (Newegg) is now out of stock on the 4-4-4-12 RAM. I've found a couple of other vendors that have it but at a higher price, about $70 US vs $55. Appreciate any suggestions.

TIA and regards.

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a b } Memory
September 17, 2010 11:16:01 PM

You will need to set the existing RAM up first to match the higher timings (higher Cas) & lower voltage of your new RAM. This will help prevent issues once you install the new RAM.
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September 18, 2010 12:08:44 AM

tecmo34 said:
You will need to set the existing RAM up first to match the higher timings (higher Cas) & lower voltage of your new RAM. This will help prevent issues once you install the new RAM.

Thanks for the reply. Not having adjusted memory timings before I assume I should do that when I first boot the new setup in the BIOS, correct? I would install the 2 GB kit that has the 4-4-4-12 2.1V (existing RAM) timings, adjust the timings and voltage, go through installing the OS (Windows 7 64-bit) and then install the new RAM sticks?
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a b } Memory
September 18, 2010 12:12:01 AM

Yes... You have listed the correct steps to take to have the greatest success using mixed timings. :) 

Hope all goes well :) 
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September 18, 2010 1:05:25 AM

tecmo34 said:
Yes... You have listed the correct steps to take to have the greatest success using mixed timings. :) 

Hope all goes well :) 

OK, thanks again. Any recommendations on tutorials or guides for adjusting memory timings in BIOS for this motherboard: GIGABYTE GA-MA785GM-US2H?
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a b } Memory
September 18, 2010 1:08:56 AM

Read through the Gigabyte stick on the main Motherboard forum page. It gives good details on Gigabyte motherboards & resources.
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September 28, 2010 1:25:48 AM

Best answer selected by highcountryrider.
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