From: sct@dcs.ed.ac.uk (Stephen Tweedie) Subject: Re: Crashing machine: >16M mem patch Date: 14 Apr 1993 23:37:11 GMT
In article <C5FF35.39J@crdnns.crd.ge.com>, davidsen@ariel.crd.GE.COM (william E Davidsen) writes:
> In article <1qa3dg$3i8@fitz.TC.Cornell.EDU>, kutcha@eos.acm.rpi.edu (Phillip Rzewski) writes:
> |
> | I recently upgraded the memory on my machine from 8 megs in 1 meg
> | simms to 32 megs in 4 meg simms. Naturally I would like to be able
> | to use all of those 32 megs from within linux. Of course that
> | meant enabling the >16M patch option in the kernel configuration.
> Please check what that patch does... I can't remember if it allows
> use of memory >16MB for programs, or turns on i/o to memory >16MB.
> If the latter is true and you have an ISA bus disk controller which
> can only address 16MB, that is likely to be the problem.
As far as I am aware, (and no doubt plenty of people will be willing
to jump down my throat if I'm wrong :-) the "enable >16MB memory"
option of the kernel just allows the kernel to use more than 16MB of
memory. It doesn't do anything special about restricting access to
memory above 16MB.
For hardware on the ISA bus which can only access memory below the
16MB boundary, it is the responsibility of that hardware's device
drivers to ensure that this restriction is respected. All of the
relevant Linux device drivers do this anyway, so although the user may
see slightly less performance doing IO with the larger memory size,
any incompatibilities with more memory should be safely hidden from
the affected hardware.
Using more than 16MB ram should be safe - the kernel configuration
script was recently changed so that allowing larger memory is now the
default.
Cheers,
Stephen Tweedie.