question about CAS Latency

[Xylob the Destroyer]

Can you mix RAM sticks of different CAS latency?

I've googled the hell out of this and can't seem to find any really concrete answers.... No definitive factual information.
Lots of speculation though -- 'it'll just run all the RAM at the slowest latency', 'it'll work in the BIOS, but crash Windows', 'it'll fry all 3 sticks'....

My ol' lady has a PC running 512MB of Corsair Platinum CL2 (DDR 333, PC2700) in her home-built PC (MSI mobo).
I picked up 3 sticks of DDR 333 PC2700 that are 256MB each, but CL2.5 (no-name stuff from an HP).

There are 3 slots on the mobo and I figured I could just drop 2 of the newly acquired sticks into the extra slots and bump her up to a nice Gig of RAM until I saw that the "good" stuff she already had was CL2.

The MSI BIOS does not have any CAS latency settings.

I don't wanna fry anything (she'll KILL me!!!!!).

For now I've just put all 3 of the CL2.5 sticks in, but it would be cool to put the old one in there to get a Gig...

Links to articles, FAQs, etc would be greatly appreciated!

TIA!!!

[driguy]

I run two different latency rams. My computer just runs them at the slowest latency.

The worst thing that could happen is YES, you could possibly bork windows. Maybe. But I doubt it. More than likely the computer just won't boot.

If you're really paranoid, unplug the hard drives, install the memory, and boot a memtest86 cd to test it, see what comes up.

[redwudz]

If you can't set the memory timings, they will just revert the the slower timings. Here's a bit of info. There are more pages there. http://www.hardwaresecrets.com/article/26/3

CAS or CL is just one of the timings, usually the first number. CPU-Z will give you lots of info on your memory modules. http://www.cpuid.com/cpuz.php

My laptop has mixed RAM modules cause I screwed up when ordering a second module.

EDIT: Wrong screenshots. I don't have access to that laptop at present.

They are CL 2 and 2.5. And they run fine. I would get better performance with CL 2, but it's just a laptop for net surfing, so not a problem.

The additional amount of memory will more than make up for a slower CL timing. My Vista computer is running timings of 4-4-4-12 at 432Mhz and the first '4', the CL, isn't a factor.

[rockaway]

Can you mix RAM sticks of different CAS latency?

I've googled the hell out of this and can't seem to find any really concrete answers.... No definitive factual information.
Lots of speculation though -- 'it'll just run all the RAM at the slowest latency', 'it'll work in the BIOS, but crash Windows', 'it'll fry all 3 sticks'....

My ol' lady has a PC running 512MB of Corsair Platinum CL2 (DDR 333, PC2700) in her home-built PC (MSI mobo).
I picked up 3 sticks of DDR 333 PC2700 that are 256MB each, but CL2.5 (no-name stuff from an HP).

There are 3 slots on the mobo and I figured I could just drop 2 of the newly acquired sticks into the extra slots and bump her up to a nice Gig of RAM until I saw that the "good" stuff she already had was CL2.

The MSI BIOS does not have any CAS latency settings.

I don't wanna fry anything (she'll KILL me!!!!!).

For now I've just put all 3 of the CL2.5 sticks in, but it would be cool to put the old one in there to get a Gig...

Links to articles, FAQs, etc would be greatly appreciated!

TIA!!!

Yes, you can mix CAS latencies, but the machine will use the highest CAS
latency of the installed chips. Sometimes you can set the CAS latency
in the BIOS and push up the latency a bit above the one set by the spd
eeprom claims the chip is rated. With CAS lower is higher, i.e. CAS 2
is faster than CAS 3. The difference in real world performance I've
found is minuscule, so I don't see the point in messing with the rated
speed. Also, in my experience, you can use PC3200 with a PC2700 machine.

[RickA]

As others here have said it will only default to run at the memory timings of the slowest chip. I really doubt one would notice the difference between CAS 3 or 2 for the normal daily computer user. The added memory capacity should more then make up for it if you are forced to a slower CAS speed.

--> The super smart thing you should do is to download a free program called MemTest86 (or MemTest64 if you have a 64bit rig). Burn the Memtest image to a disc, so you can boot off of it - ImageBurn works great. Then let the program run overnight - a minimum of several hours. What MemTest does is thoroughly checks your memory for errors. You really do not want to put faulty memory in your system because that could eventually bork Windows and /or your data.

Ah yeah, be careful of static electricity, unplug your system before sticking the new memory in there. Good luck and enjoy the added memory.

Cheers,
Rick

[Xylob the Destroyer]

thanks from the input guys.
I've continued to google the interwebs on this and still find a lot of conflicting info.
I think the ultimate answer is "It depends.".
Depends on the mobo, the RAM, the BIOS.....

Some mobo's will be able to handle it, some won't. Voltage differences between the RAM units could cause serious problems, or not. This particular BIOS doesn't really have much in the line of RAM settings, and may or may not allow the mixed stuff to function.

I did download the memtest proggie and burned it to a disc. Booted up my own PC (the one I'm typing this on right now) and the program ran for about 1 minute and then crashed with thousands of errors listed.....
I've never had any problems with this PC and it runs like a champ (it's NOT the one listed in my PC specs). Kinda makes me question the program & it's capabilities.

I think I'll try booting the disc in her PC and see if/how it works. Just for kicks.
Later this month, after she's done with finals, I'll probably stick that "good" RAM back in along with 2 of the others and see what happens.

[Xylob the Destroyer]

booted from the memtest cd on the ol' lady's PC and it "crashed" quicker than it did on mine.....
Her PC runs just fine. In fact, she commented last night how it was doing better with multiple applications open/running than it did before I stuck the extra 256MB in....

[RickA]

Most strange of your problems with Memtest. I have combed through numerous benchmarking and stability testing sites for overclockers and tweakers who want to get the most out of their systems. Memtest has always been listed up there as a lynchpin of the test programs suggested along with 3DMark, Prime95 etc for burning in and torture testing equipment.

It has helped me ferret out questionable sticks of memory for my rigs over the years. Maybe the copy you got does not like your system for some reason. Could be your memory is "iffy" and is squeeking by for your needs. Not sure what to tell you.

Glad to hear that the extra memory has helped and she is liking it.

Cheers,
Rick