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Help understanding memory usage (in Windows Vista)

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February 20, 2007 5:19:54 AM

I work at a place that sells computers, and I was looking over our various Vista systems and was rather surprised about something. No matter how much RAM they had (512MB, 1GB, or 2GB), the percentage of their physical memory used was pretty similar. I would assume that, at least, the 2GB systems should have twice as much free physical memory as the 1GB ones do. But that definately does not appear to be the case.

My understanding of memory is rather... limited. I think of RAM as the "working space" of the computer—the place things are when they're running. I know that part of the hard drive is reserved as pseudo-RAM in the form of the "page file" or "virtual memory," but I admit I don't know much about this.

So I decided to provide some specifics. Below are the make, model, basic specs, and Task Manager Peformance information for three Vista laptops. The first two are very similar aside from their RAM (and screen size), the latter not as much, but I'm trying to understand this and I would really appreciate any insights anyone could provide.

Toshiba P105-S6197:
Intel® Core™ 2 Duo Processor T5200, 2048MB PC4200 DDR2 SDRAM, 160GB (5400 RPM) SATA harddrive, 17” screen running at 1440x900, Windows Vista Home Premium
Physical Memory: Total: 2037 MB, Cached: 1369, Free: 27. Memory usage reads: 1.07GB, 54%.
Kernel Memory: Total: 136 MB, Paged: 84, Nonpaged: 52
System: Handles: 22552, Threads: 821, Processes: 78, Up Time: 63:43:33, Page File: 1050M / 4296M

Toshiba A135-S4467:
Intel® Core™ 2 Duo Processor T5200, 1024MB PC4200 DDR2, 160GB (5400 RPM) SATA harddrive, 15.4" screen running at 1280x800, Windows Vista Home Premium
Physical Memory: Total: 1013 MB, Cached: 475, Free: 9. Memory usage reads: 623 MB, 61%
Kernel Memory: Total: 104, Paged: 60, Nonpaged: 44
System: Handles: 20711, Threads: 784, Processes: 73, Up Time: 201:34:35, Page File: 977M / 2280M

HP Pavilion DV6205us:
Intel Pentium Dual Core (Core Duo, basically) processor T2060, 512MB DDR2 SDRAM, 80GB (5400RPM) SATA Hard Drive, 15.4" screen running 1280x800, Windows Vista Home Basic
Physical Memory: Total: 501 MB, Cached: 148, Free: 3, Memory usage reads: 414 MB, 82%
Kernel Memory: Total: 92, Paged: 63, Nonpaged: 28
System: Handles 17508, Threads: 776, Processes: 57, Up Time: 200:14:47, Page File: 739M / 1496M

I must admit, I don't know what the extra five processes were on the A135-S4467, but all three had nothing open when I did this except for IE7, the Task Manager, and whatever they boot up with on the Guest (limited) user.

I've heard Vista can "scale" itself somehow based upon the available system resources--is that what's happening here? If so, how? And if you had a system with 4GB of RAM, would it still find a way to use up 50% of the physical memory doing nothing? :) 

Thanks!
February 20, 2007 5:53:16 AM

Yes, I assumed SuperFetch was why the "free" memory was so low (and what the "cached" memory value was). But I also listed the "used" memory and the reading from the little performance gadget thing, which shows (as a percentage) CPU and memory usage. In both cases, this seems to be exclusing the SuperFetch used memory to make the value useful.

Problem is, the numbers don't add up: on the Toshiba P105, if you add the "cached" value to the "free" value, you get 1396 MB, which is 68% of the 2048 total memory ("32% used," IOW). The 1.07GB of used memory does add up to the 54% value on the memory usage meter, but it would mean 952.32 MB of RAM would be available, and that value isn't on the performance values.

Note, also, I'm not trying to "fix" anything on these systems--I'm just trying to understand them. I assume they're "working as intended" since they're brand-spanking new.
February 20, 2007 11:40:24 AM

I have similar problem. When Vista boots up it takes several minutes for CPU and RAM to stop jumping around and drop to normal 27% RAM usage (2 gigs).
!