Windows 7 - 4gb RAM installed, sometimes showed 2gb usable

Hi,
I have 4gb RAM on the Dell XPS 1530 machine.
I installed Windows 7 64 bit from on two partitions.
The first one, a fresh install, Computer Properties shows 4gb RAM, the same value (4096) is also showed in Task Manager.

The second one, I upgraded from Vista 64 bit, it shows 4gb RAM (2usable), the same (2048) is showed in Task Manager.

I heard the story about Memory Remap, my mainboard didn't have it. However, the first case, it automatically recognize 4gb RAM, I guess Windows7 manages everything. Is there anyway I 'turn on' the rest 2gb in the second case?

Thanks.

I had the same problem but with my xps 1530: my win 7 shows 3.50 usable. I checked the BIOS and it says memory available 4086MB and memory usable 4084MB.

SO the problem is in windows 7. Maybe it is 'cause I installed windows virtual pc, but windows 7 shouldn't reserve memory for XP when it is not on.

Well well...no idea.

Any help?

A 32bit OS is only capable of addressing 4GB of memory and that includes video memory and other memory caches too. You'll often only see 3.5GB of memory on a 32bit OS.

You'll need to upgrade to 64bit Windows 7 to see the rest.

Well at this point I am happy with that.

Thank you.

@12eason,
In both cases, I used Windows 7 64bit, even my old vista was 64bit. And I also heard about 'memory remapping' already, but 1st case (fresh install), it shows 4gb without any discrepancy, so I guess there's nothing to do with BIOS (and my BIOS doesn't have that feature).

@racoonlab,
did you find the 'memory remapping'? my BIOS version is a12, and it's the newest update from Dell already but couldn't find it.

What motherboard do you have? Have you tried finding bios updates? (long shot though as generally if the chipset supports it, it's there from the start.)

I don't know where to read to find out what motherboard it is. But it's original configuration. And I've already updated to the latest BIOS, but there's still no memory remapping. However, like I said before, 4gb is seen (and all usable) in the fresh install. So, you know a work-around?


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You can work around the amount of memory that's usable by uninstalling the devices responsible for reserving address spaces below the 4 gB limit. Unfortunately, the most common device that does this is the video card - so if you remove it you'll have more memory accessible, BUT you won't be able to see it!

No matter what the BIOS supports, 32 bit Windows client operating systems can only use the first 4 gB of installed RAM. If hardware devices reserve address space in the first 4 gB (such as the video card example above) - you won't have the full 4 gB available to you.

2 thoughts about this:
- since the reserved address spaces don't subtract from your RAM, you actually have some RAM above the 4gB limit - but you can't use it since 32 bit client systems can't "see" it. So this is "wasted" RAM. Depending on your motherboard's capabilities it may not hurt your system - but, if you haven't purchased the extra RAM yet, you may save a few dollars by doing the research first
- I wonder if an onboard video card (that uses shared RAM rather than it's own) can utilize more RAM below the 4gB limit because the reserved address space is actually using RAM for it's operations?

Here's a great article on Physical Memory: Mark's Blog : Pushing the Limits of Windows: Physical Memory

But I have 64bit Windows, and only the upgraded install (from Vista 64) got trouble, the fresh install utilize all 4gb memory.

I discourage the use of upgrade installs. They not only import the current problems that you have, but they also may import problems that weren't evident in the previous installation.

In your case I'd suspect that an incompatibility in a driver was the cause of the memory issues - but without actually recreating the problem we'll never be sure of exactly what caused it.