Vista x64 not using all my RAM (4GB)

I recently installed the 64-bit version of Vista ultimate (got it for free, so why not?) My previous OS, was the 32bit version of Vista business---post SP1, it recognized 4GB but only showed 3070MB total available in the task manager which I thought was due to the 32-bit OS limitation

However, the 64bit version only shows 3069MB total (also SP1)

CPU-Z reports 4GB installed, so what's going on? Is this a bios thing?

Laptop specs in sig.

 

What model of laptop do you have?

 

Sager 5760/Clevo M57U

 

Does your BIOS show the memory installed?

 

Yes, that appears to be it.

There's a bios screen that shows: 4096MB installed

and: 3071MB available to OS

There doesn't appear to be an option to adjust it though. Any ideas?

 

Actually, it sounds more like an address space limitation thing. This is different from the limitation with the 32-bit OS, which simply couldn't handle big enough numbers. In the chipset there is a set of logical memory addresses that can either be allocated to physical RAM bytes, or to other components in the system, one of the biggies being the dedicated graphics card, others including any PCi devices, USB, etc.

I haven't verified, but I think that this system may have a hardwired maximum to its address space of 4GB; since some of those logical addresses have to be assigned to things like your GPU and your other peripherals, that necessarily leaves less than 4GB of logical addresses to allocate to the physical RAM bytes in your memory sticks. As a result, your system simply cannot address all 4GB of physical RAM.

The closest analogy I can think of is to the banks of little mailboxes you see in the post-office - there are a fixed number of those mailboxes based on the chipset design, and each mailbox can only be assigned to one customer, and customers are either 1Byte physical RAM, 1Byte PCI, or etc. Once you've assigned all 4,096,000,000 mailboxes to one type of a customer or another, that's it. So, if you assign 1GB worth of mailboxes to your dedicated GPU customers, then the naximum number of mailboxes you can possibly assign to your physical RAM customers is 3GB, regardless of how many physical RAM customers your system can physically accomodate, and regardless of how many physical RAM customer addresses your OS could send mail to.

That help any?

 

Unfortunately, some motherboards and/or BIOSes don't support 4 gb no matter what OS you run. See if there's a BIOS update for your computer. If that doesn't fix it, then maybe it just doesn't support it. But, check in the Sager forum and/or ask the vendor you bought it from.

 

You have a 945GM/PM chipset which can only address up to 3gb memory

 

Flipfire beat me, your system had 4gb of memory address space, it has to reserve so much for the system devices so it has to use up some of that space for the 4gb.

 

I believe no platform before Santa Rosa can address more than 3 GB

 

yeah unfortunately true. no laptop mobo before santa rosa supports more than 3GB of memory.

 

Hey guys...
My apologies for reviving this very old thread, but I have exactly the same issue as the OP.
My chipset is PM45 with a Bios version 1.21 (using Acer 5930 as stated in sig).
BIOS and Windows (x64 Vista Home Premium SP1) see 4GB, but Task manager in x64 Vista sees Total Physical Ram as only 3GB (same is with the advanced Boot options in msconfig ... it's fixed on 3GB and won't budge).

Is it possible that I have to update the BIOS in order for the Task Manager to use/see all 4GB in x64?
Latest BIOS revision seems to be 1.23 so I could give it a go with that.

 

bump ...
could really use some help with this.