Am I correct in thinking that Virtual PC and Virtual Server do not support
anything running above the 4gb memory limit or can these packages do some
kind of address translation and use that memory? In which case with a 32bit
host on an 8gb machine 4gb would never get used?

If I were to use 64bit Vista as a host is there any way to tell Vista to put
as much as possible in high memory so my 32bit OSs can go in low memory? I
think this configuration would allow an 8gb machine to at least have the
host using memory from 5 to 8 gb.

Can Server 2008 run 32bit stuff above the 4gb memory space?

Thanks
Tom

A virtual machine is just like any 32bit computer.

<newscorrespondent@charter.net> wrote in message
news:b%fDj.71$wF4.34@newsfe02.lga...
> Am I correct in thinking that Virtual PC and Virtual Server do not support
> anything running above the 4gb memory limit or can these packages do some
> kind of address translation and use that memory? In which case with a
> 32bit
> host on an 8gb machine 4gb would never get used?
>
> If I were to use 64bit Vista as a host is there any way to tell Vista to
> put
> as much as possible in high memory so my 32bit OSs can go in low memory? I
> think this configuration would allow an 8gb machine to at least have the
> host using memory from 5 to 8 gb.
>
> Can Server 2008 run 32bit stuff above the 4gb memory space?
>
> Thanks
> Tom

32 bit is limited to 4 GB. The operating system controls which memory is
used for which functions, and (essentially) you can't change that. If you
have a 64-bit Windows machine, you have access to a far larger memory
address space - 16 Terrabytes of virtual memory address space instead of 4
GB. However, each 32-bit VM is still just a 32-bit computer.

With both Virtual PC and Virtual Server, you can run 32-bit guests on your
64-bit windows, and run more of them that way. Each 32-bit virtual machine
get's its own 4 GB of virtual memory address space, regardless of how much
physical RAM is assigned to it. And you're not limited to 4 GB of physical
RAM for either of those products.

With Hyper-V, you can ONLY run 64-bit host (but it's now called the parent
partition). You can still run 32-bit guests (child partitions) on Hyper-V.
They don't have any more available memory than they would in any other
virtualization - it's the limit of a 32-bit operating system that uses a
flat memory model.

--
Charlie.
http://msmvps.com/xperts64
http://mvp.support.microsoft.com/profile/charlie.russel


<newscorrespondent@charter.net> wrote in message
news:b%fDj.71$wF4.34@newsfe02.lga...
> Am I correct in thinking that Virtual PC and Virtual Server do not support
> anything running above the 4gb memory limit or can these packages do some
> kind of address translation and use that memory? In which case with a
> 32bit
> host on an 8gb machine 4gb would never get used?
>
> If I were to use 64bit Vista as a host is there any way to tell Vista to
> put
> as much as possible in high memory so my 32bit OSs can go in low memory? I
> think this configuration would allow an 8gb machine to at least have the
> host using memory from 5 to 8 gb.
>
> Can Server 2008 run 32bit stuff above the 4gb memory space?
>
> Thanks
> Tom

Thanks, so it will load a 32bit OS anywhere it can find space even giving it
4gb between 12 and 16gb.

sort of. Actually, you might want to read the blog post I just put up on
memory, RAM and memory address space. It was written in answer to another
post on the 64bit newsgroup, but it might you understand the
differences between RAM and virtual memory address space.

--
Charlie.
http://msmvps.com/xperts64
http://mvp.support.microsoft.com/profile/charlie.russel


<newscorrespondent@charter.net> wrote in message
news:mNCDj.213$Du5.181@newsfe02.lga...
> Thanks, so it will load a 32bit OS anywhere it can find space even giving
> it
> 4gb between 12 and 16gb.

Saying that a 32bit app gets a 4gb address space still does not say where
that space is. Can it be anywhere or does it have to be in a physical
address that can be recognized by a 32bit piece of code or can it be
someplace else and something makes it think the memory it sees the kind of
addresses it is expecting.

I think you are say that my 32 bit code must always be in physical address
below 4gb. If I host with 64bit OS all of my 32bit stuff still runs in the
first 4gb of memory.

No. memory is not necessarily contiguous, and virtual memory address space
is entirely under the control of the OS. It could reside anywhere.

What you really need to stop doing is thinking of _any_ direct correllation
between RAM and memory. Physical RAM is not memory. It's merely one place
that memory is stored.

You should never think of an address space as being in a particular
location. Except for the very first steps of the boot process, that is never
the case. Memory is mapped into the address space, and that address space
may be linked to RAM, to HD, or be simply virtualized. So it is entirely
possible for me to have 5 32-bit VMs running on 64-bit Windows, each with an
assignment of 2 GB of memory. That takes 10 GB of RAM (because of the way MS
virtualization uses memory and RAM for virtualization), but it that does not
mean that any particular piece of RAM is used for a particular VM - that's
entirely up to the underlying OS (or hypervisor) to manage.

--
Charlie.
http://msmvps.com/xperts64
http://mvp.support.microsoft.com/profile/charlie.russel


<newscorrespondent@charter.net> wrote in message
news:B9XDj.232$%M6.24@newsfe07.lga...
> Saying that a 32bit app gets a 4gb address space still does not say where
> that space is. Can it be anywhere or does it have to be in a physical
> address that can be recognized by a 32bit piece of code or can it be
> someplace else and something makes it think the memory it sees the kind of
> addresses it is expecting.
>
> I think you are say that my 32 bit code must always be in physical address
> below 4gb. If I host with 64bit OS all of my 32bit stuff still runs in the
> first 4gb of memory.

Perhaps a slightly different answer might .

If the host Operating System is 32 bit, then depending on which edition of
Windows it is, it might be able to actually use more than 4 GB of physical
RAM if the /PAE option is used. The /PAE option enables support in Windows
for an extension to the Intel architecture that allows the OS to map virtual
memory pages into physical addressess above 4 GB. The page at
http://technet2.microsoft.com/window....mspx?mfr=true
recommends that PAE be enabled "if appropriate".

The /PAE option does not change the size of each individual process's
virtual address space - that remains at 4 GB maximum. What it does is
allows the OS to allocate (map) any part of any virtual address space into
any page of physical RAM by using a 36 bit physical address instead of a 32
physical address. Since there are always multiple processes running in a
Windows environment, each of which could theoretically allocate 2 GB of
private virtual memory, using the /PAE option allows more processes and more
virtual memory of them to be RAM resident at any one time.

Virtual addresses - used by processes (applications, tasks) uses 32 bits
Physical address - used by the processor to address physical RAM uses 36
bit.

You might find the article at
http://members.shaw.ca/bsanders/Wind...ageFileEtc.htm
useful.

If you are running 64 bit Vista, you automatically have support in the host
OS for at least 8 GB RAM (Home Basic -8, Home Premium -16, all others -
128+). With the 64 bit edition of Virtual Server you can take full
advantage of this RAM. The OS and Virtual Server will map the 32 bit Guest
OS virtual address space pages into a RAM page anywhere in the Physical
memory.

Whether the (host) OS is 64 bit or is 32 bit with /PAE, the "4 GB boundary"
for physical memory essentially does not exist - all physical RAM pages are
treated equally regardless of their physical address (well, purist might
argue that some physical addressses are "special" becuase of the way the
Intel architecture and related hardware works, but for most practical
purposes, this doesn't really matter- the host OS takes care of these
"special cases" transparently to applications).

--
Bruce Sanderson
http://members.shaw.ca/bsanders

It is perfectly useless to know the right answer to the wrong question.



<newscorrespondent@charter.net> wrote in message
news:B9XDj.232$%M6.24@newsfe07.lga...
> Saying that a 32bit app gets a 4gb address space still does not say where
> that space is. Can it be anywhere or does it have to be in a physical
> address that can be recognized by a 32bit piece of code or can it be
> someplace else and something makes it think the memory it sees the kind of
> addresses it is expecting.
>
> I think you are say that my 32 bit code must always be in physical address
> below 4gb. If I host with 64bit OS all of my 32bit stuff still runs in the
> first 4gb of memory.