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I currently have 4gb RAM on my PC. Although I have a 32 bit OS, it can see 3.3gb. I now have VMs and this can cause performance issues as there is competition for resources.

I am not sure if I can buy memory which is 2gb per slot (2 x 4 = 8gb). When buying memory, what dictates compatibility (pins is one of those things I believe)?

In the case that I cannot use more memory than this, what other methods can I use to solve memory issues? I have seen software which allows you to use your USB pen as RAM (not ReadyBoost in Vista, a MS Gold Partner made some software for this but I don't know how good it is let alone the company name anymore). Would this be effective? I have slots for two HDs in my PC and both are taken. SSD as RAM is not effective due to slow write speed (or is that read?).


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Nothing can replace adding more RAM to your system. You'd be best off installing a 64-bit version of Windows and simply upgrading your computer (motherboard, RAM, etc). – Sasha Chedygov Nov 27 '09 at 18:55
This seems like my only option, but I hate the intrusiveness. Oh well. – dotnetdev Nov 27 '09 at 20:45

Your 32 Bit OS will not be able to use any additional RAM. Do you actually use all the RAM when you have the VM running? My system with 4GB will easily run Windows 2003 in a VM with 2GB assigned to the VM.

Performance issue for me is usually hard drive contention. I therefore run the VM on a separate internal drive or an external eSATA drive. I also noticed a difference with 7200RPM Western Digital Caviar Black drives. Have not tested 10,000 RPM VelociRaptor or similar.

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definitely a good tip, to run VMs on a secondary hard drive! Strongly recommended. – Jeff Atwood Nov 27 '09 at 18:57
I run my VMs on a 2nd HD (7200rpm, 64mb cache). I'm aware of the issue of 32 bit OS/4gb RAM. – dotnetdev Nov 27 '09 at 19:13
Sorry....I did not see that in the question. – Dave M Nov 27 '09 at 20:39

The easiest solution to lack of memory is ... to buy more memory! Memory is cheap!

I am not sure if I can buy memory which is 2gb per slot

You almost certainly can. While you should check your motherboard manual to be sure, I'd be shocked if anything built in the last 4 years couldn't support 2 GB DIMMs.

You will also want to upgrade to a 64-bit OS so you can use more than 4GB of memory, of course.

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I am planning to deploy Windows 7 Ultimate 64 bit. This just won't be a one weekend job but gradual as I need to keep my current dev environment running so I will use a VM, convert to virtual hard drive, and roll out to host. – dotnetdev Nov 27 '09 at 19:12

It is expected and well-known that you will not see 4GB of RAM in a 32-bit OS.

I can't speak to the efficacy of using a USB key as "memory", but you're right to suspect that it's throughput is nowhere near that of actual RAM.

How many VMs are you running? How much RAM are they configured to run with? Can you reconfigure them to use less RAM each, leaving more for your host OS?

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Which 32-bit OS and what CPU do you have in the machine?

If you are running a non-server edition of Windows or have an older CPU that isn't 64bit capable then you can not use more than 4Gb of RAM.

If you are running one of certain server editions of Windows (2000AS, 2000DC, 2003Ent, 2003DC, 2008) you can enable PAE to address more then 4Gb. PAE is not supported by all CPUs though, and it is not supported by other versions of Windows.

If you are running Linux on a 64-bit-capable chip then you can use a 64-bit kernel with a 32-bit user-space so you can use more then 4Gb without having to completely reinstall to get a fully 64-bit system. On Debian, just apt-get install <appropriate kernel package> and off you go. Each process will be limited to 3Gb of memory (real RAM plus swap) but under most VM solutions (certainly under VMWare, as I run my home server this way) this means each VM can have up to 3Gb allocated.

Before trying though, check your motherboards docs to make sure it can actually use more then 4Gb of RAM, otherwise there is nothing your OS can do to help you.

As for the SSD as swap option: you would need a good (read "good" as "not one of the cheap ones") SSD drive to make this worthwhile, and even then you will have performance issues (it will be quite a chunk faster than swapping to/from a spinning disk based drive if you get a good SSD, but not as much faster as you might hope). More real RAM is the way to go if you can.

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