Max RAM Used by Vista

[JockMullin]

Hi, folks

With XP sailing into the sunset I now must support users running Vista so I am about to get a Vista system in-house. Up till now I have had no compelling reason to use Vista and based on the sluggish performance I have seen and the compatibility tales of woe I have thus far hung back.

As with all Windows versions obviously the more memory the better. However speaking to a friend the other day, he claimed Vista 32 bit will only use 3 gig of memory. (I can't quite believe the adverb "only" is appropriate there)

This guy is usually pretty knowledgeable (a gamer) but I was wondering if this is indeed accurate.

Anyone know for sure?

Thanks, Jock

 

[dseaver]

32bit processors can only address up to 4GB of memory. therefore 32 bit operating systems are limited to 4gb of memory. Windows does something (I dont remember what, but someone else on here will) with .5 GB of memory when you use 4 gb, giving you effectively 3.5GB of memory.. The limit for 64 bit systems has a higher memory addressing limit

 

[TheLad]

Here's an explanation of sorts as to the 3Gb max question:

http://www.dansdata.com/askdan00015.htm

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[JockMullin]

Thanks, guys. Looks like my friend was right.

I also found a MS KB article here:

http://support.microsoft.com/kb/929605

which basically says if you install the max memory supported by a given version of the hardware/os (4 gig for 32 bit, 8 gig for 640 then basically the last gig or so is not available to apps since it is used for mapping device memory such as video.

What they don't say, but imply, is that if you have less memory then device/driver memory usage will take up to 1 gig of virtual. This explains a lot of the trashing that goes on under heavy memory usage.

So I guess there would be an advantage to having 4 gig of memory, even if it won't be available to apps or the OS directly as it will stop device memory usage from making them swap.

Jock

 

[dseaver]

Yea, It doesn't hurt to have 4GB, you just won't be able to use all of it unless you move to Vista 64bit. Especially if you are buying DDR2, its so cheap that its worth it

 

[linney]

Vista RAM usage and 32/64 bit differences
thread1583-1379026

Windows 4GB limit
thread779-1376159

 

[strongm]

>What they don't say ... is that if you have less memory then device/driver memory usage will take up to 1 gig of virtual.

That's because it doesn't. It devices get permanent, real addresses which cannot be used by RAM, whether virtual or real.

 

[JockMullin]

Thanks, Linney, those are both excellent links.

Though I knew the 32 bit memory addressing limitation was 4gig I hadn't twigged to the fact that included video and other device memory residing in the address space. Consequently for a 32 bit version it makes no sense to go above 3gig ram since you will only use 3.2 gig or so.

I have to agree with some comments in those threads that Vista might have included support for memory paging or mapping to allow for more ram.

Jock