Is Mixing DDR RAM latencies no big deal? (3338 vs 3448)

Got an eMac that came with one 512 meg 184 pin PC3200 Dimm. Has memory latencies of 3-3-3-8. I now have another 512 meg 184 pin PC3200 Dimm that is rated 3-4-4-8. Intent is to put the 3-4-4-8 Dimm in the machine to give me 1 gig of total memory.

Given that the eMac is not dual channel, should having a 3-3-3-8 Dimm in the first slot and a 3-4-4-8 Dimm in the second slot cause any issues? Or should it be no problem at all?

I have read on various MAC forums that some people have combined these types of Dimms together and they are working, but I’m not sure if it could cause data corruption or anything like that.

Is the worst that could happen that the memory will be just a tad slower in terms of performance? Or is data corruption or something like that possible?

Thanks very much for the help.

No data corruption, but depending on how the motherboard deals with RAM they might all run as slowly as - or slower than - the slowest chip.

Or, it might not work at all if the motherboard tries to clock the slower ones up to the speed of the faster one.

I would not mind if it slows the 3-3-3-8 down to 3-4-4-8 to match with the other chip. It is an eMac after all. :slight_smile:

I’ll plug it in and see what happens. Putting Dimms into that eMac is about as easy as pie. Takes like 30 seconds.

Basically then, all I can expect is slightly slower performance, but no data corruption or system stability problems, right?


OK, I popped the Dimm into the eMac and it booted up fine. I opened System Profiler and it reads as follows:

Memory Slot: DIMM0/J2
Size: 512 MB
Speed: PC3200U-30440

Memory Slot: DIMM1/J1
Size: 512 MB
Speed: PC3200U-30330

Is there any freeware app for OS X 10.4 that can test memory?

Appreciate the help. :slight_smile:


I’ll give it a look. Thanks. :slight_smile:

I second jimmybob’s recommendation. If you wanna test your systems stability including ram and cpu, use something like Prime95. But for just testing your memory, memtest is great at it. Just d/l memtest, it’s an iso file, so start up dvddecrypter or whatever you have to burn an iso. Set your pc to boot from CD rom, put in the disc, reboot and away it goes! It should catch any problems with your ram. Just remember to let it run a long time to know you’re ram is stable. An hour or two isn’t enough to really know, let it run for many hours, even a couple or few days to make sure.

Thanks. I am in the process of running it two full times, 3 cycles each. First one on OS X Terminal locked 400+ meg and the sequence passed. I thought about restarting and ran it from Terminal and that time since nothing else had run, it was able to lock 832 megabytes and it is finishing sequence 2 of 3. After it finishes all 3, I’ll check the log. So far, so good.

Hopefully after the tests, things will end up just fine and I can have confidence in the integrity of the data that is processed in the memory.

Thanks for the help.

Remember what I said though too. Running memtest just a couple of times doesn’t neccesarily mean your ram is solid (although it means your probably good, bad ram should usually fail pretty quickly), at least run it overnight or something, you need hours of it to know you’re good. Same with Prime95, I had one time when I was experimenting with the max overclock of my sytem. I thought I was stable after 8 hours of running Prime95, then it crapped out at 23 hours! So I had to slow things down a hair to really make it rock solid.

Also, I don’t think you need to check any logs or anything with memtest. Somewhere it will say errors 0. If it stays that way you’re good. An error will show you a visual indication and will be red, you don’t want to see that. Good luck, I think you’ll be fine, most of the time you can mix rams that aren’t exactly the same and it will work OK. You’ll just run at the speed of the slowest of the sticks, but there shouldn’t be any other ill effects.