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Comment by PythonicAlpha | Hacker News Reader

One question on behalf of this: Has anybody experiences with mixing RAM types today? My problem is, that new computers most of the time come with 4GB pre-installed (1 module), but I want to have 8GB. Get the same RAM (DDR3) is rather unlikely -- so, would you add a different RAM module to the preexisting memory module or is it better to replace it with a pair of new RAM modules?

Any experiences, opinions?

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My experience comes from an Ivy Bridge machine with a B75 chipset and 4 RAM slots, YMMV.

I had a single 2GB 1333MHz stick and bought another one second-hand. The sticks had different densities (one had 4 and the other 8 memory chips on) but timings were the same. The system would not boot with the sticks on the same bank (same slot color) but when I moved one stick to a different bank, the system booted and BIOS indicated the memory was operating in dual channel mode at correct timings. I didn't experience any issues with the system for 1 year.

If your machine only has two RAM slots with a single bank, then it's a crapshoot on whether the system will boot. With two different banks you can usually mix non-matching memory.

Huh, wierd, to my knowledge, in order for dual channel to work, they have to be on the same bank.

Yes, I would have expected the same.

Thanks to you and all others!

Unfortunately, the computer I am about to buy has only one bank (smaller size computer). I also was thinking about using the dual channel mode -- but as the speedup would not be that great, I could do without. But I guess too, usage of different modules on the same bank might be a crapshot.

The guy who sells me ram suggested I don't buy two of the same 4gb modules but the 8GB(2x4) kit of the same brand for £1 more as they're tested together. Read into that what you will.

If you want dual channel(twice the memory bandwidth), the modules should be equal.

In theory, yes. In practice, you get ~20% more bandwidth and almost no improvement in application performance.

Yeah, I've gone through 4GB -> 4GB + 8GB -> 8GB + 8GB upgrade route a few times. It works if you're short on money and can't upgrade at once.

But yeah, buy decent, trusted RAM, and run it through memtest overnight.

Just get the additional RAM from the same vendor (or Crucial or Kingston). Your mainboard will automatically change the settings to the lowest common detominator so it will work just fine.

If it doesn't work, switch the order. The timings of the modules might be different.

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