/NOLOWMEM does not work

NTDEV
1

I want to test handling of physical addresses
above 4 GB in my kernel driver.

The test system:
8 GB RAM Windows 2000 Advanced Server with all
patches installed.
The boot.ini entry: /PAE /3GB /NOLOWMEM /NUMCPUS=1

It seems that /NOLOWMEM flag doesn’t work –
Task Manager and WinDbg !vm command still show
about 8000 MB of RAM.

What can be wrong with my setup?

Dmitriy Budko, VMware

2

Just a guess: the /3GB switch is incompatible with /nolowmem

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Dmitriy Budko
Sent: Tuesday, September 14, 2004 7:56 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] /NOLOWMEM does not work

I want to test handling of physical addresses above 4 GB in
my kernel driver.

The test system:
8 GB RAM Windows 2000 Advanced Server with all patches installed.
The boot.ini entry: /PAE /3GB /NOLOWMEM /NUMCPUS=1

It seems that /NOLOWMEM flag doesn’t work – Task Manager and
WinDbg !vm command still show about 8000 MB of RAM.

What can be wrong with my setup?

Dmitriy Budko, VMware

Questions? First check the Kernel Driver FAQ at
http://www.osronline.com/article.cfm?id=256

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3

> On Behalf Of Mark Roddy

Just a guess: the /3GB switch is incompatible with /nolowmem

It should compatible according to
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEdrv.mspx

“The /PAE, /NOLOWMEM and /3GB switches, and the registry change,
can be used at once. Note that /3GB will prevent access to physical
memory beyond 16 GB because the kernel memory space is reduced
with the /3GB switch, and thus does not have enough room for the additional
Page Table Entries required when memory is larger than 16 GB.”

Dmitriy Budko, VMware

4

Just confirmed that if you specify /3GB, then /NOLOWMEM is ignored. On
Windows Server 2003 SP1 and later, you can use /NOLOWMEM with /3GB.

I’ll add this to the Boot Options doc in the DDK.

Thanks,
June Blender
DDK Tools
xxxxx@microsoft.com

“Mark Roddy” wrote in message news:xxxxx@ntdev…
> Just a guess: the /3GB switch is incompatible with /nolowmem
>
>> -----Original Message-----
>> From: xxxxx@lists.osr.com
>> [mailto:xxxxx@lists.osr.com] On Behalf Of Dmitriy Budko
>> Sent: Tuesday, September 14, 2004 7:56 PM
>> To: Windows System Software Devs Interest List
>> Subject: [ntdev] /NOLOWMEM does not work
>>
>> I want to test handling of physical addresses above 4 GB in
>> my kernel driver.
>>
>> The test system:
>> 8 GB RAM Windows 2000 Advanced Server with all patches installed.
>> The boot.ini entry: /PAE /3GB /NOLOWMEM /NUMCPUS=1
>>
>> It seems that /NOLOWMEM flag doesn’t work – Task Manager and
>> WinDbg !vm command still show about 8000 MB of RAM.
>>
>> What can be wrong with my setup?
>>
>>
>> Dmitriy Budko, VMware
>>
>>
>>
>>
>> —
>> Questions? First check the Kernel Driver FAQ at
>> http://www.osronline.com/article.cfm?id=256
>>
>> You are currently subscribed to ntdev as: unknown lmsubst tag
>> argument: ‘’
>> To unsubscribe send a blank email to xxxxx@lists.osr.com
>>
>
>
>
>
>