Re: large memory support for x86

From: Richard B. Johnson (
Date: Thu Oct 12 2000 - 12:27:14 EST

On Thu, 12 Oct 2000, Oliver Xymoron wrote:

> On Wed, 11 Oct 2000, Kiril Vidimce wrote:
> > My primary concern is whether a process can allocate more than 4 GB of
> > memory, rather than just be able to use more than 4 GB of physical
> > memory in the system.
> Define allocate. There are tricks you can play, but userspace is still a
> flat 32-bit address space per-process.

--- per process. Which means, in principle, that one could have 100
processes that are accessing a total of 400 Gb of virtual memory.

It gets to be a bit less than that, though. Process virtual address
space doesn't start at 0

Script started on Thu Oct 12 13:25:45 2000
cat xxx.c
    printf("main() starts at %p\n", main);
# gcc -o xxx xxx.c
# ./xxx
main() starts at 0x8048488
# exit
Script done on Thu Oct 12 13:26:08 2000

Dick Johnson

Penguin : Linux version 2.2.17 on an i686 machine (801.18 BogoMips).

"Memory is like gasoline. You use it up when you are running. Of
course you get it all back when you reboot..."; Actual explanation
obtained from the Micro$oft help desk.

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