Windows 7 - XP 32 bit Memory

Asked By John Callaway

17-Nov-09 04:54 AM

How much memory can XP 32 bit OS handle? I want to have Dell build a
dual boot Laptop with both Windows 7 OS & XP 32 bit OS on it. I would
like to have 8 Gig of ram if it XP 32 will handle it.

JPC

17-Nov-09 06:30 AM

Windows XP 32-bit supports a maximum of 4GB of RAM but due to address
space requirement for hardware addressing you will not be able to use
the full 4GB, depending on the hardware installed in the machine the
available RAM could be anywheres between 2.75 to 3.5GB.

John

17-Nov-09 09:34 AM

It will not handle it. Neither will Windows 7 (unless it is 64-bit
Windows 7). Moreover, it is very likely considerably more than you can
make effective use of in either operating system.

Here is the scoop:

All 32-bit client versions of Windows (not just Vista/XP/7) have a 4GB
address space (64-bit versions can use much more). That's the
theoretical upper limit beyond which you can not go.

But you cannot use the entire 4GB of address space. Even though you
have a 4GB address space, you can only use *around* 3.1GB of RAM.
That's because some of that space is used by hardware and is not
available to the operating system and applications. The amount you can
use varies, depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. it is usually around
3.1GB.

Note that the hardware is using the address *space*, not the actual
RAM itself. If you have a greater amount of RAM, the rest of the RAM
goes unused because there is no address space to map it to.

--
Ken Blake, Microsoft MVP (Windows Desktop Experience) since 2003
Please Reply to the Newsgroup

17-Nov-09 10:03 AM

The most a 32 bit version of Windows can have is 4 GB.  That said it is
unlikely that you will ever see more that 3.2 GB of free memory.  This is
because all of your devices attached to your PC take up memory address
spaces for things they need to work (i.e. drivers, etc).


--

Roy Smith
Windows XP Pro SP3

18-Nov-09 08:26 PM

OK. I get it. I will only get 3 gig for ram.
Now what do you think of the idea of a dual boot for XP 32 and windows
7 on the same laptop?  Having XP 32 the default OS and using windows 7
when I choose, using a 64 bit processor around 3 gHrtz? I am wondering
about driver compatibility etc and using XP 32 bit OS with a 64 bit
processor.

JPC

19-Nov-09 09:07 AM

What would be the point? It is possible to dual boot, you will have to visit
the laptop mfg's website to see if they provide Windows 7 drivers. There
will be no compatibility issues between x64 hardware and an x86 operating
system, it is been going on for years.

--


--

19-Nov-09 06:48 PM

[]
Is this why many netbooks have a maximum of 2G?
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf
** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously
outdated thoughts on PCs. **

19-Nov-09 11:19 PM

No that is a hardware limitation and has nothing to do with Windows RAM
size limit.


--

Roy Smith
Windows XP Pro SP3

20-Nov-09 12:43 AM

John Callaway formulated the question :

Use the remaining 5Gb as a RAM drive for temporary files etc.
http://www.trap17.com/index.php/4gb-Xp-32bits_t67548.html

--
/klaus

05-Dec-09 10:49 AM

32 bits' OS only suport 3,25 Gig. More than that you have to install a 64 bits.

05-Dec-09 11:42 AM

Sorry, that is not correct. The number is variable. Here is the way it
works:

All 32-bit client versions of Windows (not just Vista/XP/7) have a 4GB
address space (64-bit versions can use much more). That's the
theoretical upper limit beyond which you can not go.

But you cannot use the entire 4GB of address space. Even though you
have a 4GB address space, you can only use *around* 3.1GB of RAM.
That's because some of that space is used by hardware and is not
available to the operating system and applications. The amount you can
use varies, depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. it is usually around
3.1GB.

Note that the hardware is using the address *space*, not the actual
RAM itself. If you have a greater amount of RAM, the rest of the RAM
goes unused because there is no address space to map it to.



--
Ken Blake, Microsoft MVP (Windows Desktop Experience) since 2003
Please Reply to the Newsgroup

06-Dec-09 06:31 AM

MVP" <kblake@this.is.an.invalid.domain> writes:
[]
[]
Since the hardware presumably does not need much, presumably the RAM
_beyond_ the hardware address _could_ be used, if someone were to write
a suitable "memory manager" (as used to be done in the early days of DOS
to get round the "640k" limit (and even a little around 1M, IIRR).
Unless the hardware uses incomplete address decoding, that is.

If such a manager were to be written, of course, only software that knew
about it could use it (like DOS software that either knew about being
usefulness for it to be worth anybody's while, since software houses
would be unlikely to cater for it.
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf
** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously
outdated thoughts on PCs. **

Odds are, the phrase "it is none of my business" will be followed by "but".

07-Dec-09 07:34 AM

That will not happen on NT operating systems, the kernel will simply not
allow it.

John

06-Dec-09 09:42 AM

Ken Blake,
I do appreciate all the info on this matter. I recently
purchased a Dell laptop with W7 OS. I could not install some older
programs on it, so I tried to install XP 32 bit OS on a  partition
that I resized with W7. The CD/DVD drive would not fully load the
install disc. I returned the computer. I have since done some research
and found out that if I have XP 32 Bit OS on the computer and then
load W 7 on it, it seems to go better. So I intend to buy another Dell
with W 7 OS, then resize the partition, making room for XP 32 bit OS
on the other partition. I will then Ghost the W 7 partition using
Norton. I will then load XP 32 bit OS over the W 7 OS providing the
CD/DVD will read the XP install disc. Then Ghost the W 7 OS on the
other partition. I have downloaded EasyBC boot loader utility to have
the option to dual boot to which OS I want on boot up.
Ken, am I on the right track?

John P. Callaway

06-Dec-09 10:26 AM

Sorry, although I'd like to help if I could, I have never had any
interest in dual-booting and know next to nothing about it.

Perhaps someone else here can answer your question.

--
Ken Blake, Microsoft MVP (Windows Desktop Experience) since 2003
Please Reply to the Newsgroup

06-Dec-09 07:26 PM

Absolutely no need for "3rd-party boot loaders" as Win7 will easily cope with
multi-booting Windows NT-based OSs (although, personally, I have had some problems
getting the NT bootloader to boot MS-DOS-based Windows...).

==

Cheers,    Tim Meddick,    Peckham, London.    :-)

07-Dec-09 03:24 AM

I was not talking about boot loaders, but memory managers. (Which John
says will not happen.)

--
J. P. Gilliver. UMRA: 1960/<1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf
** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously
outdated thoughts on PCs. **

Politicians are much like ships: noisiest when lost in a fog.

07-Dec-09 03:44 PM

There is built-in support in the kernel for an application to map
unmanaged memory.

07-Dec-09 04:00 PM

AWE, only for the applications own use, you cannot develop a memory
manager around this, the kernel will not allow this to manage other
processes' memory.  On 32-bit systems AWE will only be able to access
RAM above the 4GB barrier if the operating system is PAE capable, 32-bit
XP cannot do it.  Few applications are AWE capable, this is mostly
reserved for large database programs and other such applications.

John

07-Dec-09 04:13 PM

I am not talking about AWE, but about mapping "device" space (physical
memory). That way you can use memory above 4G also in 32bit XP.

XP supports PAE. Its own memory manager just does not allow access to
memory above 4G.

07-Dec-09 04:43 PM

XP supports PAE for DEP only, drivers and applications cannot access the
memory above the 4GB barrier.  From what I understand memory above the
4GB barrier was available with PAE when XP was released but too many
drivers were misbehaving and causing BSODs so Microsoft decided to put
an end to this in SP1.

I know that a certain RAM disk can apparently make use of the memory
above the 4GB barrier, I guess this is what you mean by "device space".
Although the RAM drive can map the space for use as temporary storage
for other applications the other applications still cannot use this for
their process space, the memory manager does not permit any applications
to directly manage other processes' space.  Other than snake oil memory
memory optimizers there are no third party memory managers for NT
operating systems.

John

07-Dec-09 05:01 PM

With device space I mean this:
http://msdn.microsoft.com/en-us/library/ms801998.aspx

And yes, some ram-disks uses that to use memory above 4G.


True, you need a bit more to use that kind of memory for other than data
storage.

07-Dec-09 08:39 PM

writes:

When I suggested a memory manager, I was not talking about going beyond
the 4G limit, I was talking about accessing the RAM within the 4G but
beyond where hardware sits on some machines, i. e. using non-contiguous
memory.
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf
** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously
outdated thoughts on PCs. **

Reality and talent shows lack honesty. They manipulate the viewer with mawkish
stories. Contestants turn tragedies into qualifications. - Sean Lock, in Radio
Times, 20-26 June 2009

07-Dec-09 09:11 PM

That is a hardware problem that you cannot solve with software. That is
why the memory remapping function were invented.

07-Dec-09 09:48 PM

Thanks for the link.  In one of his blogs Mark Russinovich said that
SKUs to ignore physical memory that resides above 4GB, even though they
can theoretically address it."  My understanding about this is that
while (some of) the server versions can do this the whole point of
limiting memory access below 4GB on clients with PAE was to specifically
prevent drivers from playing in the upper memory arena.  So now I am not
sure what to think...

http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx
Mark's Blog : Pushing the Limits of Windows: Physical Memory

John

08-Dec-09 03:25 AM

writes:

They seemed to solve it OK in the days of DOS and the (I think it was)
640K barrier, with LOADHI (IIRR) and so on; ISTR prog.s and drivers had
to be loadhigh aware, or something like that. it is all a Long Time Ago
...
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf
** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously
outdated thoughts on PCs. **

Reality and talent shows lack honesty. They manipulate the viewer with mawkish
stories. Contestants turn tragedies into qualifications. - Sean Lock, in Radio
Times, 20-26 June 2009

08-Dec-09 06:19 AM

You also do not use this function to allocate memory. All the memory
allocation functions that the drivers (normally) use will always
allocate memory below 4G in 32bit XP.

08-Dec-09 06:25 AM

The problem with not all 4GB being usable is because MMIO is overlapping
the address space where your RAM lives. All memory addresses in that
region are redirected to the IO-system. So you cannot get to that RAM.

Memory remapping solves that by remapping ram in that region up above
4G, so you can address it there instead (which 32bit XP does not do
willingly).

24-Dec-09 07:33 PM

There is another teensy weensy problem.
Microsoft using various means, does not allow legal modification of windows
core by "outsiders" to allow relocation to "unused" memory.
Since hardware, with a proper memory manager, in hardware and software,
usually can do such things, the problem ends up going back to Microsoft's
code.
After all, memory mapping is a very old technique, going back to the
minicomputers, if not farther back in history.  Some of the minicomputers
had an rough equivalent to Windows swap file, in that if enough memory was
installed, resided in memory rather than only on disk.  At one point, some
of HP's systems swapped out almost anything that was not currently in use.
The ops system maintained a table that was used to find everything.
(1970's) long before Apple, etc.  One of the major problems is the
compatibility issue with older P/C hardware and "standards" that are the
result of "IBM compatibility", based on a crippled hardware design intended
to prevent competition with mainframe capabilities and save hardware costs.
The older schemes also were usually intended for use with multiusers, be the