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RAM issue - on Opteron

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Anonymous
a b à CPUs
March 26, 2005 10:54:29 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

Hi.
I have a question about RAM and WinXP. I know that XP has very bad RAM
management (when I say RAM I mean physical RAM), so it uses just a
half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
(I need lots of memory: 3D+video work), I'm not happy about it, but it
wouldn't be such a problem by it self (I can buy as twice as RAM).
However, I heard that XP can (support up to 4GB, but can) use only 2GB
of physical memory (RAM). Now, I intend to buy dual Opteron system.
That means that each procesor has it's own RAM (HyperTransport aside).
If I give each procesor 2 GB of RAM (4GM total), would it work, or
would XP see it as 4 GB?

Another thing; I heard that Win2K has much better RAM management than
XP. Is it true?

More about : ram issue opteron

Anonymous
a b à CPUs
March 26, 2005 12:06:07 PM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

xscript wrote:
> Hi.
> I have a question about RAM and WinXP. I know that XP has very bad
RAM
> management (when I say RAM I mean physical RAM), so it uses just a
> half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
> (I need lots of memory: 3D+video work), I'm not happy about it, but
it
> wouldn't be such a problem by it self (I can buy as twice as RAM).
> However, I heard that XP can (support up to 4GB, but can) use only
2GB
> of physical memory (RAM). Now, I intend to buy dual Opteron system.
> That means that each procesor has it's own RAM (HyperTransport
aside).
> If I give each procesor 2 GB of RAM (4GM total), would it work, or
> would XP see it as 4 GB?
>
> Another thing; I heard that Win2K has much better RAM management than
> XP. Is it true?

With 32 bit addressing there is potentially 4 GB of address space, but
some of this is reserved for video memory and I/O. In practice,the
32-bit versions of Windows won't see more than about 3.2 GB of RAM,
depending on the address space reserved in the bios for the AGP
aperture. Also, the address space is partitioned so that no more than 2
GB is available for applications. The exceptions occur if any of the
/PAE, /3GB or /userva switches are set in the boot.ini file (see
http://support.microsoft.com/default.aspx?scid=kb;en-us;833721).
However, these are not intended for general use.

I've been involved with a project where the available address space in
a Windows 2000/XP environment is a concern and have not seen seen
anything that would indicate that Windows XP Professional is not at at
least as good a choice as Windows 2000. Also, it potentially offers an
upgrade path to the 64-bit version of Windows that is already available
as beta software.

Robert
March 26, 2005 2:37:24 PM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

On Sat, 26 Mar 2005 07:54:29 -0800, xscript wrote:

> Hi.
> I have a question about RAM and WinXP. I know that XP has very bad RAM
> management (when I say RAM I mean physical RAM), so it uses just a
> half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
> (I need lots of memory: 3D+video work), I'm not happy about it, but it
> wouldn't be such a problem by it self (I can buy as twice as RAM).
> However, I heard that XP can (support up to 4GB, but can) use only 2GB
> of physical memory (RAM). Now, I intend to buy dual Opteron system.
> That means that each procesor has it's own RAM (HyperTransport aside).
> If I give each procesor 2 GB of RAM (4GM total), would it work, or
> would XP see it as 4 GB?

There is a lot of misinformation floating out there and I haven't
tried memory > 2GB, so maybe here's some more on the pile. ;-) As I see
it, both processors can see all the RAM, so XP will see 4GB in your
proposed system. I don't think that's going to work. I see your
alternatives are Linux now and as much memory as you can afford (16GB
max), wait for XP-64 (has been due "any time now" for a coupla years), or
1GB per processor. Or of course some combination of the above with
upgrades.
>
> Another thing; I heard that Win2K has much better RAM management than
> XP. Is it true?

I've heard that, but I've heard so many conflicting reports that I
wouldn't trust any. Personally, I have no use for XP.

OTOH, M$ says that Win2K Server will support 4GB, and Advanced Server 8GB,
so _perhaps_ that's another alternative.

http://www.microsoft.com/windows2000/serverfamily/defau...

....and the below site says that 2000 XP (home and professional) will
support 4GB (only 2GB for apps).

http://www.ultratech-llc.com/kb/?File=MaxRAM.TXT
Related resources
Anonymous
a b à CPUs
March 26, 2005 8:01:50 PM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

xscript wrote:
> Hi.
> I have a question about RAM and WinXP. I know that XP has very bad RAM
> management (when I say RAM I mean physical RAM), so it uses just a
> half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
> (I need lots of memory: 3D+video work), I'm not happy about it, but it
> wouldn't be such a problem by it self (I can buy as twice as RAM).
> However, I heard that XP can (support up to 4GB, but can) use only 2GB
> of physical memory (RAM). Now, I intend to buy dual Opteron system.
> That means that each procesor has it's own RAM (HyperTransport aside).
> If I give each procesor 2 GB of RAM (4GM total), would it work, or
> would XP see it as 4 GB?
>
> Another thing; I heard that Win2K has much better RAM management than
> XP. Is it true?

Why not make all of your XP and W2K concerns irrelevant and use
the 64 bit version of XP when it is released ? That currently is
scheduled for April.

When using the 64 bit XP, each 32 bit app will be limited to 4
GB, but when 64 bit versions of your apps come out they will be
able to use all of the available RAM.
Anonymous
a b à CPUs
March 26, 2005 8:20:50 PM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

keith wrote:
> On Sat, 26 Mar 2005 07:54:29 -0800, xscript wrote:
>
>
>>Hi.
>>I have a question about RAM and WinXP. I know that XP has very bad RAM
>>management (when I say RAM I mean physical RAM), so it uses just a
>>half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
>>(I need lots of memory: 3D+video work), I'm not happy about it, but it
>>wouldn't be such a problem by it self (I can buy as twice as RAM).
>>However, I heard that XP can (support up to 4GB, but can) use only 2GB
>>of physical memory (RAM). Now, I intend to buy dual Opteron system.
>>That means that each procesor has it's own RAM (HyperTransport aside).
>>If I give each procesor 2 GB of RAM (4GM total), would it work, or
>>would XP see it as 4 GB?
>
>
> There is a lot of misinformation floating out there and I haven't
> tried memory > 2GB, so maybe here's some more on the pile. ;-) As I see
> it, both processors can see all the RAM, so XP will see 4GB in your
> proposed system.

XP and W2K will both see all the RAM and will use all of it, but
individual processes are limited to 2 GB each.

> I don't think that's going to work. I see your
> alternatives are Linux now and as much memory as you can afford (16GB
> max), wait for XP-64 (has been due "any time now" for a coupla years), or
> 1GB per processor. Or of course some combination of the above with
> upgrades.

Apparently MicroSoft has firmed up on the RTM date and expects to
start shipping to OEMs in April. I also know someone who has 8
dual Opteron systems using RC2 (release candidate 2) and he is
quite happy with it - he just wants his 64 bit PhotoShop
yesterday. (Actually "Premiere Pro" rather than simply PhotoShop.)

However, even his current PhotoShop is better on RC2 simply
because it can use the available RAM better than it could under
the 32 bit version of XP.
Anonymous
a b à CPUs
March 27, 2005 1:28:25 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

On 26 Mar 2005 07:54:29 -0800, xscript@net.hr (xscript) wrote:

>I have a question about RAM and WinXP. I know that XP has very bad RAM
>management (when I say RAM I mean physical RAM), so it uses just a
>half (or so) of avaliable RAM.

Err, no. WinXP will definitely use all your available RAM if the
application demands it, though whether or not it will do so in an
intelligent manner is another question. This is actually somewhat
application-dependent too, so it's tough to generalize too much.
Generally speaking though, WinXP does tend to make a rather large disk
cache, so a lot of your memory (half?) might be used for this purpose,
sometimes starving the actual application of memory. In theory the
disk cache should only use memory that is not otherwise being used,
but that is not always the case.

Generally speaking though, Win2K and WinXP do a fairly good job at
managing memory. They are *WORLDS* beyond what was available in
Win9x.

> Since I intend to buy over 2 GB of RAM
>(I need lots of memory: 3D+video work), I'm not happy about it, but it
>wouldn't be such a problem by it self (I can buy as twice as RAM).
>However, I heard that XP can (support up to 4GB, but can) use only 2GB
>of physical memory (RAM).

Per application, yes, err... sorta. This is kind of a 32-bit
limitation which does not apply in the case of 64-bit chips like the
Opteron and 64-bit OS, like WinXP for x64 systems (still in the late
beta stages but to be released soon). A 32-bit chip can only properly
address 4GB of memory, however the OS has to map some of that memory
for it's own functions. By default in Windows the OS takes 2GB of
memory for itself and leaves 2GB for the application. However Windows
CAN be set to only take 1GB for itself and allow 3GB for the
application, but not all applications are designed to accommodate this
feature.

Just as a FWIW, this isn't really a Windows limitation, as Linux has
the exact same issue (it defaults to 1GB/application, 3GB for the OS
but can be set the other way around in the kernel).

> Now, I intend to buy dual Opteron system.
>That means that each procesor has it's own RAM (HyperTransport aside).
>If I give each procesor 2 GB of RAM (4GM total), would it work, or
>would XP see it as 4 GB?

XP will see it as 4GB of memory in a NUMA setup with 2GB attached to
each processor.

>Another thing; I heard that Win2K has much better RAM management than
>XP. Is it true?

Not in the least. In fact, the reverse is true, at least as far as
the Opteron is concerned. Win2K is not at all NUMA-aware, in the
above example it would see your memory as a flat 4GB set of memory.
WinXP is at least a bit NUMA-aware and can actually tell that some
memory is best left with some processor/application. My understanding
is that the NUMA implementation in WinXP is not quite up to the level
of Solaris, but it's better than Linux at this time.


The long story short is this: If your application needs 2GB of memory
for itself, you really want to have more than 2GB of memory total.
The OS *WILL* take some of the memory for itself to be used as a disk
cache, for I/O and for services. If you're working with large video
files and can afford 4GB of memory then it might not be a bad idea to
get it. Along these lines though, it may also be very worthwhile for
you to look into getting WinXP for x64 systems when it becomes
available (presumably within the next few months).


Ohh, one final point of note. If you put 4GB of memory in a system
and run 32-bit Windows on it you will almost certainly not see the
full 4GB in the OS. The BIOS will show all the memory, but the OS
will probably only show your system as having ~3.2GB of memory. This
is because some of that memory is being mapped for I/O. The OS does
actually SEE all of the memory, but can't make use of it for general
purpose stuff, so it's somewhat hidden. 32-bit limitation, won't be
an issue in WinXP for x64 systems.

-------------
Tony Hill
hilla <underscore> 20 <at> yahoo <dot> ca
Anonymous
a b à CPUs
March 27, 2005 2:15:59 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

xscript wrote:
> Hi.
> I have a question about RAM and WinXP. I know that XP has very bad RAM
> management (when I say RAM I mean physical RAM), so it uses just a
> half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
> (I need lots of memory: 3D+video work), I'm not happy about it, but it
> wouldn't be such a problem by it self (I can buy as twice as RAM).
> However, I heard that XP can (support up to 4GB, but can) use only 2GB
> of physical memory (RAM). Now, I intend to buy dual Opteron system.
> That means that each procesor has it's own RAM (HyperTransport aside).
> If I give each procesor 2 GB of RAM (4GM total), would it work, or
> would XP see it as 4 GB?

XP would see the RAM as one big 4GB pool rather than two separate 2GB
pools.

Now as for XP's alleged bad "RAM management", what specifically are you
referring to? If you're referring to controlling the RAM, then that's
outside the control of the operating system, that's done entirely by the
system's memory controller, which as you may know is inside the
northbridge chipset in Intel systems, and inside the CPU itself in AMD
systems. It's completely out of the control of the OS, and very
transparent to it.

However, the OS does control how the RAM is allocated. And there is some
very wierd cases where it's been found that a system actually slows down
if they put more than 2GB of RAM in it. This I believe is an Windows
XP32 bug. I'm not sure what causes it, but it's annoying, and it's not
going to be a problem with XP64.

> Another thing; I heard that Win2K has much better RAM management than
> XP. Is it true?

I doubt it. It's the same operating system family.

Yousuf Khan
March 28, 2005 5:26:23 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

On 26 Mar 2005 07:54:29 -0800, xscript@net.hr (xscript) wrote:

>Hi.
>I have a question about RAM and WinXP. I know that XP has very bad RAM
>management (when I say RAM I mean physical RAM), so it uses just a
>half (or so) of avaliable RAM. Since I intend to buy over 2 GB of RAM
>(I need lots of memory: 3D+video work), I'm not happy about it, but it
>wouldn't be such a problem by it self (I can buy as twice as RAM).
>However, I heard that XP can (support up to 4GB, but can) use only 2GB
>of physical memory (RAM). Now, I intend to buy dual Opteron system.
>That means that each procesor has it's own RAM (HyperTransport aside).
>If I give each procesor 2 GB of RAM (4GM total), would it work, or
>would XP see it as 4 GB?
>
>Another thing; I heard that Win2K has much better RAM management than
>XP. Is it true?
IIRC, WINNT/WIN2K/WINXP by default allocates 2GB per app., so, even if
you have more than that, the reminder will be used for Windows itself
and other apps if you happen to multitask. I also remember that Win2k
Advanced Server may be (officially allowed by MS) modified to use up
to 3GB per app (is a registry trick involved or anything else? -
Google for it, and you will find it). Is this available to Win2kPro
or XP? Maybe as a hack, but not officially. IMO, your best bet is
WinXP64 - available now as beta, and will be officially released soon.
As for allocation between the processors - I'm not sure how it works,
but I can tell you from my own experience that you will hardly notice
the difference between accessing the memory directly attached to the
CPU or going through another CPU. The difference may amount to a few
percents under certain benchmarks, but you will not see it while
running everyday tasks (including DVD encoding using apps like Nero).
!