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VS512MB400 and VS512MB400C3 compatibility


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I built my computer about 1.5 years ago and at the time included 1 gig (2x512) ram from Corsair - the model was VS512MB400C3. Along with other upgrades to my system, I recently decided to upgrade to 2 gigs of ram. I ordered the kit that contains 2x512 of VS512MB400C3 but Zipzoomfly sent me 2x512 of VS512MB400 (no C3). I immediately noticed the serial number difference but after a quick look at the specs on the website concluded they were identical.


To make a long story short - I installed them and they seemed to work fine except eventually I noticed my ram was running at 100mhz (ddr200) instead of 200mhz (ddr400). After investigating the matter I learned that Zipzoomfly actually sent me CAS2.5 instead of CAS3 - meaning they actually sent me better ram than what I ordered. When I have all 4 sticks in there telling the bios to configure my ram by spd yields radically different results than telling it to do it by spd when I only have either just the CAS3 or just the CAS2.5 ram in there.


A few of the many things I've tried - all of which have resulted my system being unable to POST:

Changing the BIOS setting to DDR400 (leaving the rest at AUTO).

Changing the BIOS to the higher of all the spd values and setting it to DDR400

Changing the BIOS to the lower of all the spd values and setting it to DDR400


I also tried changing the BIOS settings to the higher of all the spd values but leaving it at DDR200 and this allowed me to boot (of course my memory was still only behaving like DDR200).


I don't see why I can't make this CAS2.5 memory just behave like CAS3.0. I can do an RMA but I feel silly doing so since they actually sent me better memory than I ordered. Is there a way to make these 4 DIMMs work together or do I need to go ahead and switch out the CAS2.5 with 2 more CAS3s to make it compatibility.


Thanks in advance,


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  • Corsair Employees

This may be the limit of the configuration you have, with this MB when you install more than 2 double sided modules the memory controller will by default down clock the memory to DDR200 to DDR333. But all of the modules have to identical with this MB and mixing memory that was made at different times even the same part# is not suggested. You can submit an RMA request and ask our customer service if they can replace all of your modules would be the best I can suggest!

Please use the RMA request found in TSXpress or follow the link in my signature “I think I have a bad part!” and we will be happy to replace them or it! And please note that you are from the forum!

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