Anyone know why? I have Vista 32-bit Home Ultimate, and I know it's supposed to support 4 GIG. Why does it only see 2.8 GIG?

Because 32-bit systems cannot read anymore than 3.25Gb of RAM
It's a built in system limitation.
Which is why 64-bit systems are available for those who want more.

With a 32-bit system, you'll read ~2.75-3.25 Gb of RAM maximum, dependant upon your computer.

Ah, I heard it was 4 gig...

Some memory is reserved for system service and devices at POST time.

But as I've read, SP1 will make Vista report all 4 Gigs but not make use of it all.

None of those are true. 32bit windows OS sees 4GB of ALL physical memory. This includes lots of things about address space that I am ueducated on but memory allocated to video and the works, to include memory physically residing on your GPU.

you must have a lot of video ram to address as well
perhaps SLI setup?

for
the
love
of ALL THAT IS GOOD AND GREAT in this miserable world

can we please have a sticky that explains this?

honestly...

(Thanks to Scotteq for saving this answer on a file so others can post it when this qustion is asked at least once a week. To the mods: can we have a sticky about this using Scotteq's file as the main post?)

In 32 bit Windows operating systems, the total addressable space available is 4GB. If you installed total 4GB memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions, such as:

- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- Configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices

Different onboard devices and different add-on cards (devices) will result of different total memory size. e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.

This limitation applies to most chipsets & Windows XP/Vista 32-bit version operating systems.

If you install a Windows operating system, if more than 3GB memory is required for your system, then the below conditions should be met:

1. The memory controller which supports memory swap functionality is used. The latest chipsets like Intel 975X, 955X, Nvidia NF4 SLI Intel Edition, Nvidia NF4 SLI X16, AMD K8 and newer architectures can support the memory swap function.

2. Windows XP Pro X64 Ed. (64-bit), Windows Vista 64, or other OS which can address more than 4GB memory.



Note: According to the latest Change Log published my Microsoft, Windows Vista 32bit SP1 will display the installed amount of RAM. This is a display change only.

Definitely an SLi or Crossfire setup.. Thats the only way to reduce the OS memory that much.