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Conflict with PC2100 & PC3200 RAM

Posted on 2006-04-15
Medium Priority
Last Modified: 2013-11-10
Is there a reason why I can not run PC 2100 & pc 3200 ram at the same time.

Here is the issue.  I had 1 GB ( 2   512MB sticks of pc 2100 ram)

I added 2 GB ( 2  1 GB pc3200 ) ram.  Everything booted up fine and life seemed good.

After a hour or so I launched BF2 to play.  It loaded up ok , but right before the round started my pc just shut down and re-booted.

This happened twice.  I then pulled out all the RAM and just put the 2 new 1 GB sticks in.  Every thing is fine now, but I would really like to put the othe 1 GB in to have a total of 3 GB in the machine.

Can I do this with the ram I have.
Oh yeah a few other details.  I have an ASUS 4p-800-e MOBO
2.8 GHz p4.
The board is supposed to support up to 4GB ram.

Thanks for your help
Question by:73Spyder

Expert Comment

ID: 16460112
You can not run memory at 2 diffrent speeds. Memory has to be run at the speed of your slowest memory stick in your case oc 2100. i.e. Your PC 3200 ram has to be forced to run at a lower speed.
This can be done in your Bios settings. I don't know exactly where on the ASUS board, but if you go into bios there will be a setting to slow the memory down.

Also you can try installing the memory, enuring that the slower memory (the pc2100) is in the 1st bank. On some motherboards this will force all the other memory sticks to run at the same speed
LVL 14

Expert Comment

ID: 16460137
make sure you've got identical modules in each channel (each of the two colors of memory slots is a channel). put the slower memory in the blue slots.

make sure the modules are the same cas latency.

you may have to manually lower the speed of the memory in the bios to the slower speed in order for the two different speed modules to play together nicely.

Author Comment

ID: 16460156
I had / have the modules in the the right channels.

I did not try and change the speed in the bios.  I will try this and report the results back.  Thanks for the great ideas.
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LVL 15

Expert Comment

by:Juan Ocasio
ID: 16460475
Your PC3200 memory sticks should run at the slower speed.  I would try pulling the 2 512 sticks and just run with the new one to see what your results are.  Msot MOBOs will automatically detect the speeds and run at the slower clock speed.


Expert Comment

ID: 16460496
His PC3200 will run at the slower speed only if they are designed to.  Many times, cheap ram will not downclock, which means you can't mix speeds.  If you have name brand ram, like Kingston or OCZ, you should have no problem getting the PC3200 to downclock.

Author Comment

ID: 16460563
the 3200 Is Patriot brand.

I tried all the above and could not get it to work right yet
the odd thing was that my 3dmark 03 score was 500 points lower with the 3GB in the pc that when I just had the 2GB in there.

the pc ran fine and the test ran fine, but bf2 kept crashing.

so, far now I just have the 2gb in the pc

LVL 70

Accepted Solution

garycase earned 2000 total points
ID: 16461540
I would NOT recommend you mix the memory for several reasons:

(1)  As noted already, if you mix memory speeds, all of the memory will run at the slowest speed.   You don't need to make any changes in the BIOS -- the reported SPD info from the memory will cause this to happen automatically.   Note also that although memory manufacturers claim full downward compatibility, there are often issues when running higher speed modules at lower speeds -- and you've apparently encountered this.   It's always best to use the correct speed memory for your specific system.  With a 2.8GHz P-IV that is DDR400 (PC3200) memory, so that's what you should use.

(2)  The difference in performance on systems with 2GB vs 3GB is very unlikely to be noticeable in most applications.   In fact, as you've discovered, with a choice of 2GB at PC3200 vs 3GB at PC2100 you'll get much better performance with the PC3200.   That's why your 3D Mark score is so much better -- it's exactly what I'd expect to happen.

(3)  Mixing modules may also cause the system to switch to single channel mode, which will even further reduce your performance (it may not do this if both sets are correctly matched; but in most cases all modules have to have the same SPD timing info for dual channel to be enabled).

(4)  r.e. your comment "... The board is supposed to support up to 4GB ram."  ==> It will support up to 4GB of installed RAM, but even if you did that you wouldn't "see" all of it.   You didn't note which OS you're running, but I'll assume it's XP.  In that case, due to address  allocation in the upper end of the 4GB address space for various system elements (BIOS shadow, AGP aperture, video BIOS shadowing, etc.) you will not "see" all of the memory if you install 4GB;  on most systems you'll see a bit over 3GB (usually between 3.2 and 3.5GB) -- or notably less if you have a 512mb video card or especially SLI cards.   I never recommend installing more than 3GB with XP, and the simple fact is there's really no good reason to install more than 2GB.   I've seen systems (with dual 512mb video cards) where less than 2.5mb was "seen."

(5)  If you really feel compelled to install all 3GB, you CAN adjust the BIOS timing to even more conservative settings than the SPD info causes it to set (e.g. use more conservative latency settings for both row and column accesses) ==> this MAY allow you to install 3GB and run reliably.   BUT, the system would almost certainly be SLOWER than it will be with just the 2GB of PC3200 installed -- so I can think of NO reason you'd want to do this.    If you really want 3GB (just to emphasize it, I very much doubt you'd notice ANY difference from your current 2GB -- except in benchmarks) you should buy another pair of 512mb PC3200 sticks.

Bottom Line:   Leave your 2 PC3200 sticks installed and enjoy :-)   (Use your other memory in another PC;  sell it on e-bay;  give it to a friend; etc.)


Author Comment

ID: 16465350

Thanks for the info.  I think you are correct.  I would rather not mess with the BIOS.  I am going to leave the 2 GB  in and in a few months.  Order a matching set so that all will be the same.


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