Re: 4GB on Laptop?
- From: Bill Waddington <william.waddington@xxxxxxxxxx>
- Date: Mon, 30 Jul 2007 06:42:54 -0700
On Sun, 29 Jul 2007 18:42:38 +0200, zirias@xxxxxxxxxxxxx (Felix M.
Palmen) wrote:
* Ron Hardin <rhhardin@xxxxxxxxxxxxxx>:
Is there any advantage to 4GB of RAM, or is 3GB the most that can
be used, what with address space for devices, on a 32bit PC, in Linux.
What do you mean by address space for devices?
IIRC, hardware device registers and memory mapped regions get mapped
into the upper physical address range. If the chipset supports 4G of
RAM address space, the BIOS may limit this to 3GB or so to leave room
for device mapping.
The virtual address space on IA32 is 4GB -- so /one/ single process can
never use more memory on that architecture. Linux reserves 1GB of this
address space for the kernel. But this has nothing to do with the amount
of physical RAM that can be used. It just means a single process can't
use more than 3GB.
Linux issues aside, the hardware itself may create this limit. The OP
should check the laptop specifics before "wasting" actual RAM. IIRC
(again) chipsets up to at least Intel 945 may force this kind of
limit on BIOS. SantaRosa chipsets supposedly aviod the problem, but
I haven't verified that.
Bill
--
William D Waddington
william.waddington@xxxxxxxxxx
"Even bugs...are unexpected signposts on
the long road of creativity..." - Ken Burtch
.
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- From: Ron Hardin
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