I just picked up a used Thinkpad X60 for the road, and am maxing out the memory on it. According to the docs, it can handle 3GB max, with a total of 2 slots.

In the same breath, the docs mention "always install memory in matched pairs". OK. Nobody sells 1.5 GB RAM chips, so what's a guy to do?

  • one 1GB and one 2GB?

  • two 2GB and hope it will know to only use 3GB total?

migrated from serverfault.com Jul 18 '09 at 12:13

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I've never come across a motherboard that would become damaged by installing mismatched pairs. Just slow performance and/or refusing to boot until the ram was removed. I'd recommend just trying it out and seeing what happens.


It's possible to use 2GB + 1GB, and I've seen many strange combinations working just fine, including 512MB + 256MB.

Assuming you already have some memory installed, just put an 2GB module and give it a try for a few days. If you run in stability problem, just buy another identical 2GB module.


I'm surprised it's asking for matched pairs, but if that is accurate, then you'll need to do 2x2GB and waste 1GB. When it says "handles 3GB max", it means that the chipset won't address any more than 3GB, so any extra memory just won't be seen by the OS.

  • What would be the downside of doing 2+1? Would it perform noticeably worse? – Jason Kester Jul 18 '09 at 8:51
  • @Jason that depends on the mother board, I've had some that would act as if the memory was bad, give it a try it 2+1 works go with it. – Unkwntech Jul 18 '09 at 9:10
  • On many motherboards, the penalty for mismatched pairs is as bad as 40% in some artificial benchmarks. In most real-world applications, the effect is pretty small, 2%-3%. – David Schwartz Aug 24 '11 at 23:09

I'd buy 2x2Gb: you may use them somewhere later :) There should be no problems with your chipset anyway.


If you happen to have memory chips available, you could try 2+1. Either the docs are overly protective and it works anyway, or it will only use 1+1, or perhaps not work at all.

The safer road is of course to buy 2+2 so that you get matching pairs. Memory is rather cheap nowadays.

There are some other limitations that play in when you try to use 4 GB on a laptop (but might not be relevant in your case):

A 32 bit system can't use more than 3.5 GB. The rest of the address space is reserved for hardware.

It's common for motherboards that is a year old or so, not to be able to use more memory than 3.2 GB.


I would also recommend just going for the 2x2. Who knows, you might install the 64bit version of Vista or Windows 7 someday and get to use all 4 GB :)


Take a look at supplier recommendations. Taking two local suppliers I use as examples, for an X60, Crucial recommend a maximum of 2GB as 2 x 1GB but MemoryC recommend 4GB as 2 x 2GB (though, of course, you would only fully benefit from that with an OS that can use that much memory). Results from your local suppliers may differ. You need to make sure you use the exact description of the machine when deciding which components are correct.

Remember, too, that to access larger memory amounts, a BIOS upgrade may be needed so check the manufacturer's recommendations on that.

Finally, more RAM generates more heat and this can be an issue that affects, at least marginally, the operation and longevity of the machine as well as increasing costs, reducing battery life and increasing heat output.


From Lenovo's Support Website:

Memory 256MB, 512MB, 1GB, or 2GB and supports up to 4GB maximum memory Note: Only 64-bit operating systems support more than 3GB of system memory (RAM). Intel Chipsets 945GM and 945PM do not support more than 3GB system memory (RAM), even when a 64-bit operating system is installed.

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