How much a Windows OS uses...

[Jest3r]

About a year ago I was under the impression that it was like this:

XP 32 Bit - 2 gigs
XP 64 Bit - 4 gigs
Vista 32 Bit - ~3.4 gigs
Vista 64 Bit - ~6.7 gigs

I have a feeling that this information is incorrect. Anyone have more accurate information?

 

[Samalama]

Well first of all, Google is your friend: http://en.wikipedia.org/wiki/64-bit#32_vs_64_bit

And to answer your question...
XP 32 Bit - 4 GB
XP 64 Bit - 128 GB
Vista 32 Bit - 4 GB
Vista Home Basic 64 Bit - 8 GB
Vista Home Premium 64 Bit - 16 GB
Vista Ultimate 64 Bit - 128 GB

 

[mpilchfamily]

Actually any 64 bit OS should be able to use a heck of allot more RAM then 128G. Not that any motherboard will have that kind of support any time soon. Not i'm not sure if the OP is asking about the max amount of RAm that it can address or what the minimum it needs to fuction.

 

[tcsenter]

Originally posted by: Jest3r
Anyone have more accurate information?

Yes. This is much more precise:

XP 32 Bit - 4GB minus whatever the BIOS gives to hardware
XP 64 Bit - 128GB minus whatever the BIOS gives to hardware
Vista 32 Bit - 4GB minus whatever the BIOS gives to hardware
Vista 64 Bit Basic - 8GB minus whatever the BIOS gives to hardware
Vista 64 bit Premium - 16GB minus whatever the BIOS gives to hardware
Vista 64 bit Business, Enterprise, and Ultimate - 128GB minus whatever the BIOS gives to hardware

If the hardware imposes physical memory decoding limits that are less than the OS limit, then for all OS it is:

- hardware memory limit minus whatever the BIOS gives to hardware

Actually any 64 bit OS should be able to use a heck of allot more RAM then 128G.

Should but won't because Microsoft hard-limits the kernel even in 64-bit OS for product segmentation (i.e. marketing) reasons.

 

[mpilchfamily]

Good to know.

Thanks

 

[pallejr]

tcsenter, are you sure that MMIO is included in this calculation (for 64bit)? In XP, before SP2, it was 4GB RAM + MMIO. They changed that in SP2 due to driver issues (that issue doesn't exist here).

 

[tcsenter]

Originally posted by: pallejr
tcsenter, are you sure that MMIO is included in this calculation (for 64bit)? In XP, before SP2, it was 4GB RAM + MMIO.

MIMO = included in what BIOS gives to hardware

 

[pallejr]

Do you know for sure, or do you have some documentation? I'm just curious, because the amount of address space needed for MMIO is not included in that "x number of GB" in all editions, like I said.

 

[tcsenter]

Originally posted by: pallejr
Do you know for sure, or do you have some documentation? I'm just curious, because the amount of address space needed for MMIO is not included in that "x number of GB" in all editions, like I said.

Since it is entirely hardware/configuration dependent, the OS developer couldn't give any estimate of this, only the computer builder or hardware manufacturer could.

 

[pallejr]

I don't think we are on the same page. If the hardware supports 8GB address space, and you have 4GB RAM and 2GB MMIO. You then remap, lets say, 2GB. That gives 4GB RAM and 6GB address space. Before SP2, XP would accept this, because you still only have four GB RAM.

The same goes with bigger configs, like 16GB RAM with a 64GB hardware supported address space.

 

[tcsenter]

Originally posted by: pallejr
I don't think we are on the same page. If the hardware supports 8GB address space, and you have 4GB RAM and 2GB MMIO. You then remap, lets say, 2GB. That gives 4GB RAM and 6GB address space. Before SP2, XP would accept this, because you still only have four GB RAM.

Correct, which works out according to my statement:

hardware memory limit (8GB) minus whatever BIOS gives to hardware (2GB) = 6GB available for addressing RAM

 

[pallejr]

Your statement: "Vista 64 Bit Basic - 8GB minus whatever the BIOS gives to hardware"

If the hardware can address 64GB, and any overlapped RAM is remapped, what then?

 

[tcsenter]

If the hardware can address 64GB, and any overlapped RAM is remapped, what then?

What is the difference between that and installing 32-bit XP or Vista on hardware that can support 16GB? The OS limit is no different than the hardware limit in its practical effect on system addressing.

If the OS kernel is hard-limited to 8GB, it might as well be the hardware limit itself. The OS can't reach anything over 8GB no matter if the hardware is capable of more.

 

[pallejr]

We are talking about the artificial memory limitation that Microsoft put in their OS. If they cap this one at 8GB. How do they count to eight gigabyte? Is it in address space, or just in RAM?

If it is in address space, it will be 8GB minus MMIO, no matter how much address space the hardware supports.

If it is in RAM, it will be fully 8GB RAM, if there is enough addresses in the hardware.

If we take XP: before SP2, they counted to 4GB in RAM. After SP2, they now count to 4GB in address space. So even if you enable PAE and memory remapping, you can never fully use 4GB RAM.