Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have 2 x 1GB on 800Mhz CL4 memory in my PC. I'm planning to upgrade to 6GB by adding a pair 2GB modules.

Is it ok if I buy CL5 modules or do I have to buy CL4?

share|improve this question
What operating system are you using? You should be aware that you need to run a 64-Bit system to support more than 3,5GB of RAM. – xor_eq Jul 15 '10 at 12:54
I plan to upgrade to windows 7 64bit – user42966 Jul 15 '10 at 12:57
i have just done the same and pc is running ok , 2x1GB CL4 Sticks and added 2x2GB CL5 Sticks , just trying to research these settings i think the sticks have different stats ex 5-5-5-18 i think the newer ones are less so not sure if i have to alter settings in bios or not :-) – user378754 Oct 12 '14 at 8:09
Not true on two counts. 1) a 32 bit OS can use way more memory with PEA. 2) The 3.5GB is not 3.5GB but 4GB minus PCI[e] address space. It is often rounded to 3.5GB but it can be more and it can be way less. 3.5 is a nice average though. – Hennes Oct 12 '14 at 13:37
up vote 2 down vote accepted

yes, should be fine, but all will run at CL5.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.