Computer Memory ?

[rg32]

Hopefully this isn't a "Can't fix stupid question"!

Any truth to this?
I’m in the process of upgrading the memory in both of my laptops and was told because of possible compatibility problems (even though the Spec. are the same) it is not advisable to mix RAM from different manufacturers.
Thanks Ron

[jziegler]

How much memory do they have now, and how much do you want? Most laptops that I've seen have 2 slots. Most of the time, both will be filled at the factory since 2 smaller modules are cheaper than 1 large one, and in some cases, two matched modules are faster (basically if you have dual channel support). I'm pretty familiar with the low level details of the DDR memory specification (and somewhat with DDR2, not as much). There is no reason that I know that that you can't mix for compatibility. But, if you want dual channel, they modules must match.

Also, you will not damage anything by trying to mix. The worst that happens is that it won't work, you take one out, and it's fine after that.

Another thing to remember is that modules from most mainstream vendors will use chips from whatever company is cheaper that week. Or, modules of the same size could have a different number of chips to get the same total. This is the type of problem that can really cause trouble with mixing for dual channel.

If you post specific information here we might be able to help out a little more (laptop manufacturer and model, current memory....)

Jim

[skruffy]

Unless you are obsessive about getting every last nanosecond of performance out of your systems, go ahead and mix away.

Even though the overall spec may be the same, say PC4200, the timings of the actual chips may vary. This is harmless and the worst that will happen is that a faster chip will slow down a bit to match the slower chip. Benchmarking software may detect this, but you won't.

[bthere]

Yes, these days it doesn't matter. Mix and match works just fine as long as all of the modules indvidually function correctly, they will work well together.

This notion that you can't mix brands is a holdover from many years ago when there were problems with memory modules and the memory controller interactions. These days it is just a folklore issue.

[TheRic]

In general you can mix, but it may not work correctly 100%. It may give strange things every once in a while. Normally it works fine or not at all.
I have several computers in house (at work) that I have mixed memory in. If you match up the memory, you will have less problems.

If you have mixed memory, and you have problems, you are going to wonder if the mixed memory is the problem. Mixing the memory also cuts down on the dual channel, as jziegler mentioned.

On important machine I match the memory, on unimportant ones I'll try putting in one of the spares I have available.

[LinuxRandal]

Basically, for the dual channel use (lower end of the spectrum/home user), or at the other end, ecc server memory in a high end system (mission critical).

For the average home user, unless you see problems like random boots and such, most people would never notice.


One trick learned by a friend of mine, he told his friends he was upgrading his memory and his old memory was available. Then he upgraded to two sticks of the same brand/type (not neccasarily the same batch).

[crokett]

Considering that my company sells memory that has different manufacturers for the same part number you don't need to worry about it. The only problems we see with memory is when the manufactuer lets something get out of tolerance on the line.

[scorrpio]

It primarily has to do with latencies, which is especially crucial for dual-channel. Latencies must match precisely in order for it to work right, and best way to ensure matching latencies is to use chips from same line.

Oh, and another issue is that more 'generic' RAM venors tend to have larger latency variance margins - meaning that their timing could be quite a bit off - but again, same line chips are likely to err by the same amount.

But quality RAM is usually way more precise. You can take a 4-4-4-12 Corsair module, pair it with a 4-4-4-12 Crucial module, and they should run just fine.

[cgallery]

We don't mix within a channel. We will mix outside of a channel. So, if your notebook supports dual-channel (a technique to enhance memory r/w speed), I'd not mix. If it doesn't, I'd go ahead and mix.

Even more important is to TEST. Get a copy of Memtest76 (either www.memtest86.com or www.memtest.org) and test it for a few passes.

Both the above testers have free versions available. No need to spend money.