Mixing different speed memory modules

Posted on 2005-03-10
Medium Priority
Last Modified: 2011-08-18
I am running a MSI K7T266 Pro2 Motherboard (MS-6380) with 512mb or Crucial Memory # CT6464Z265 with the following stats - DDR PC2100 - UNBUFFERED - NON-ECC - DDR266 - Voltage: 2.5V - Memory Timings:CL=2.5.
I am trying to add a second 512mb module.  I found a great deal at TigerDirect on the following Ultra brand memory - DDR PC3200 - 400mh  - (I apologize, but no other stats are available...)
I can install either memory module into my PC and it will work properly.  I can do this in any of the three Memory Slots on the Motherboard.  When I install both together, the PC only sees 512mb of memory.  I have tried upgrading the BIOS, changing the BIOS settings, swapping the slots several times and everything else that I can think of.  
Can I mix these two types of memory in a PC?  From what I have read, I should be able to do this, but it seems that I can not.  Any suggestions?


Question by:cellis4766
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
LVL 92

Expert Comment

ID: 13514927
you can check the compatibility at


but i think your mobo is just picky about them
LVL 69

Expert Comment

ID: 13516652
I agree - in most cases, you can mix different speed RAM, but some motherboards just don't like it.
LVL 13

Accepted Solution

Watzman earned 500 total points
ID: 13522623

Generally, you can mix speeds, but you must operate the system at the speed of the slower of the two modules.  The problem can arise because most modern memory modules have an "SPD" chip (serial presence detect), a ROM that lets the computer "READ" the specs of that memory module.  If two such modules conflict, the computer might not configure the system in a useable manner (this would be a function of the BIOS code).  You can try a manual over-ride in the BIOS and see if that helps.

There are other incompatabilities that can arise, the general rule that you can mix speeds isn't hard and fast, it's just a guideline.

From your post, I'd say that you clearly cannot mix THESE two memory modules in that motherboard.

Featured Post

Enroll in August's Course of the Month

August's CompTIA IT Fundamentals course includes 19 hours of basic computer principle modules and prepares you for the certification exam. It's free for Premium Members, Team Accounts, and Qualified Experts!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Basic computer tune-up with little or no hardware upgrades. Giving an old computer a tune-up usually results in a minimal performance gain, but a gain nonetheless. Several times a week, I’m faced with users at work who ask to make their computers…
Windows 7 does not have the best desktop search built in. This is something Windows 7 users have struggled with. You type something in, and your search results don’t always match what you are looking for, or it doesn’t actually work at all. There ar…
Finding and deleting duplicate (picture) files can be a time consuming task. My wife and I, our three kids and their families all share one dilemma: Managing our pictures. Between desktops, laptops, phones, tablets, and cameras; over the last decade…
Visualize your data even better in Access queries. Given a date and a value, this lesson shows how to compare that value with the previous value, calculate the difference, and display a circle if the value is the same, an up triangle if it increased…
Suggested Courses

765 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question