[H-GEN] where does linux load first in memory?

[David Jericho]

[ Humbug *General* list - semi-serious discussions about Humbug and  ]
[ Unix-related topics.  Please observe the list's charter.           ]
[ Worthwhile understanding: http://www.humbug.org.au/netiquette.html ]

Darrin Mison <staeci at yahoo.com> wrote:

> Been reading Mueller's Upgrading and Repairing PC's 12ed and discovered
> that most intel-esque cache controllers can only cache the first 64Meg
> of RAM.  According to Mueller Win9x and NT load into the top of the
> memory first (don't know why) so unless you need it you really
> shouldn't use more than 64Meg in order to maximise performance.

Slight false hood there. The TX series of chipsets didn't have enough tag
ram to cache above the first 64MB. Linux users on those systems instead
would create a ramdisk in the top x meg of ram, and then swap to that.

As ram sizes in desktops have increased, the limitation that the TX chipset
suffered has since been removed. If your system can support x mb, chances
are it can cache all x mb.

> So my question is: does linux load into the top of the memory first as
> well?  And does anyone know why?

Unless they've changed it in recent kernels, Linux has always loaded bottom
up. This is why you can get away with using the "mem=<blah>M" option to
specify more ram than your system actually has, and still have it run upto a
point.[1]

If your flatmates machine is crashing with the full 96MB, I'd say you've got
a dodgey [SD]IMM in there. Or you're just running Windows.

[1] I wish Linux did cool things like Windows. I remember once I installed
Windows and it told me I now had a RAID controller, three parallel ports and
a partridge in a pear tree. Be nice if Linux just added more RAM to my
system as I needed it.[2]
[2] I'm off to play CounterSkill^H^H^H^Htrike now. ;)

-- 
David Jericho, Systems Administrator
WebMatchit Interactive Marketing Ltd


--
* This is list (humbug) general handled by majordomo at lists.humbug.org.au .
* Postings to this list are only accepted from subscribed addresses of
* lists 'general' or 'general-post'.