Mixing DDR3 RAM with different CAS Latency?

This is a discussion on Mixing DDR3 RAM with different CAS Latency? within the Tech Board forums, part of the Community Boards category; I currently have 2x1GB DDR3 with 9-9-9-26 CAS Latency. I see they have 2x1GB DDR3 with 9-9-9-20 CAS for really ...

  1. #1
    and the hat of sweating
    Join Date
    Aug 2007
    Location
    Toronto, ON
    Posts
    3,545

    Mixing DDR3 RAM with different CAS Latency?

    I currently have 2x1GB DDR3 with 9-9-9-26 CAS Latency.
    I see they have 2x1GB DDR3 with 9-9-9-20 CAS for really cheap now.
    If I filled up my other 2 RAM slots with the 9-9-9-20 RAM, would that cause problems/crashes...?
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  2. #2
    Kernel hacker
    Join Date
    Jul 2007
    Location
    Farncombe, Surrey, England
    Posts
    15,677
    Most memory controllers have separate settings for each bank. If not, you may have to resort to manual settings and force the CAS latency to the longer time - that should work fine.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Internet Superhero
    Join Date
    Sep 2006
    Location
    Denmark
    Posts
    964
    If not, you may have to resort to manual settings and force the CAS latency to the longer time - that should work fine.
    Or, if the stock speed of the memory is higher than the FSB, downclock the memory to get an FSB: DRAM ratio of 1 and then it should be possible to get the 9-9-9-26 to run at 9-9-9-20..
    Last edited by Neo1; 01-20-2009 at 02:48 AM.
    How I need a drink, alcoholic in nature, after the heavy lectures involving quantum mechanics.

  4. #4
    Hail to the king, baby. Akkernight's Avatar
    Join Date
    Oct 2008
    Location
    Faroe Islands
    Posts
    717
    Hmm... So if you want to upgrade your RAM, it ain't just plug and play? Or more specific, you can't just plug it into the motherboard and it all works fine?
    Currently research OpenGL

  5. #5
    and the hat of sweating
    Join Date
    Aug 2007
    Location
    Toronto, ON
    Posts
    3,545
    Quote Originally Posted by Neo1 View Post
    Or, if the stock speed of the memory is higher than the FSB, downclock the memory to get an FSB: DRAM ratio of 1 and then it should be possible to get the 9-9-9-26 to run at 9-9-9-20..
    I'm already sort of doing that. My RAM is 1333MHz, but I run it at 1066MHz to match with my FSB...

    Quote Originally Posted by Akkernight View Post
    Hmm... So if you want to upgrade your RAM, it ain't just plug and play? Or more specific, you can't just plug it into the motherboard and it all works fine?
    Welcome to the wonderful world of computer upgrades.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  6. #6
    C++まいる!Cをこわせ!
    Join Date
    Oct 2007
    Posts
    23,025
    Quote Originally Posted by Akkernight View Post
    Hmm... So if you want to upgrade your RAM, it ain't just plug and play? Or more specific, you can't just plug it into the motherboard and it all works fine?
    But you can. Usually, when plugging in multiple memory modules with different latency, the motherboard will typically use the highest latency to make sure all the ram modules work.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  7. #7
    Kernel hacker
    Join Date
    Jul 2007
    Location
    Farncombe, Surrey, England
    Posts
    15,677
    Quote Originally Posted by Elysia View Post
    But you can. Usually, when plugging in multiple memory modules with different latency, the motherboard will typically use the highest latency to make sure all the ram modules work.
    That is if you are lucky! If you are not so lucky, they run at the highest speed, and some memory reads randomly go wrong because the RAM isn't ready to deliver the data when the processor fetches it...

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  8. #8
    C++まいる!Cをこわせ!
    Join Date
    Oct 2007
    Posts
    23,025
    The tricky part is that all motherboards are different... but a setting could fix that.
    Installing the same latency memory should be just plug n' play (assuming they have the same clockspeed, as well).
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  9. #9
    Internet Superhero
    Join Date
    Sep 2006
    Location
    Denmark
    Posts
    964
    Quote Originally Posted by cpjust View Post
    I'm already sort of doing that. My RAM is 1333MHz, but I run it at 1066MHz to match with my FSB...
    Then try to force the modules to run @ 9-9-9-20 and test with memtest86, if it works then you can get a set of 9-9-9-20 modules and run them all at the same latencies...
    How I need a drink, alcoholic in nature, after the heavy lectures involving quantum mechanics.

  10. #10
    and the hat of sweating
    Join Date
    Aug 2007
    Location
    Toronto, ON
    Posts
    3,545
    Quote Originally Posted by Neo1 View Post
    Then try to force the modules to run @ 9-9-9-20 and test with memtest86, if it works then you can get a set of 9-9-9-20 modules and run them all at the same latencies...
    Yeah, that sounds like a good idea. I'll try that before buying some new RAM.

    If I had to go the other way around and set the faster RAM to 9-9-9-26, could that cause any problems? I wouldn't expect it would, but who knows...
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  11. #11
    Captain Crash brewbuck's Avatar
    Join Date
    Mar 2007
    Location
    Portland, OR
    Posts
    7,274
    As has been pointed out, you are limited by the slowest RAM. Unless you literally can't buy the slower RAM anymore, I'm not sure why you'd get faster RAM (unless it's actually cheaper) only to have it run as slow as the slowest RAM. At today's prices I'd simply throw away your slower DIMM and start over.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  12. #12
    and the hat of sweating
    Join Date
    Aug 2007
    Location
    Toronto, ON
    Posts
    3,545
    Quote Originally Posted by brewbuck View Post
    As has been pointed out, you are limited by the slowest RAM. Unless you literally can't buy the slower RAM anymore, I'm not sure why you'd get faster RAM (unless it's actually cheaper) only to have it run as slow as the slowest RAM. At today's prices I'd simply throw away your slower DIMM and start over.
    2GB of 9-9-9-26 RAM costs about $75.
    2GB of 9-9-9-20 RAM costs about $50.
    Don't ask me why.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  13. #13
    Captain Crash brewbuck's Avatar
    Join Date
    Mar 2007
    Location
    Portland, OR
    Posts
    7,274
    Quote Originally Posted by cpjust View Post
    2GB of 9-9-9-26 RAM costs about $75.
    2GB of 9-9-9-20 RAM costs about $50.
    Don't ask me why.
    Probably because they aren't making it anymore.

    Given that new info, I'd probably eBay my old DIMM (wouldn't expect to get $75 for it, but at least something)
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  14. #14
    and the hat of sweating
    Join Date
    Aug 2007
    Location
    Toronto, ON
    Posts
    3,545
    Quote Originally Posted by Neo1 View Post
    Then try to force the modules to run @ 9-9-9-20 and test with memtest86, if it works then you can get a set of 9-9-9-20 modules and run them all at the same latencies...
    I just tried setting my underclocked RAM to 7-7-7-20 and Vista's Memory Test didn't find any problems. I think I'll get the faster RAM and just leave it set to 7-7-7-20.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  15. #15
    and the hat of sweating
    Join Date
    Aug 2007
    Location
    Toronto, ON
    Posts
    3,545
    OK, my 4GB OCZ Platinum RAM just arrived.
    When I plugged in both that and my old 2GB OCZ Gold RAM, my system wouldn't boot, but if I only plugged in 1 of the OCZ Gold modules in along with my new RAM (with a total of 5GB) then everything boots just fine.

    Any ideas why it would boot with 5GB but not 6GB? I'm guessing it has to do with having both of them in dual channel mode at the same time...
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

Page 1 of 2 12 LastLast
Popular pages Recent additions subscribe to a feed

Similar Threads

  1. RAM upgrade
    By BobS0327 in forum Tech Board
    Replies: 6
    Last Post: 12-10-2008, 08:14 AM
  2. Programming and RAM
    By spveer in forum C Programming
    Replies: 3
    Last Post: 06-16-2005, 12:17 PM
  3. Low latency sound effects
    By VirtualAce in forum Game Programming
    Replies: 0
    Last Post: 12-21-2004, 01:58 AM
  4. mixing ram types. sdram and ddr
    By Waldo2k2 in forum Tech Board
    Replies: 8
    Last Post: 05-14-2003, 06:29 PM
  5. pointerz
    By xlordt in forum C Programming
    Replies: 6
    Last Post: 01-11-2002, 08:31 PM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21