Re: 16 MB -> 32 MB, a memory problem resolved!

Ingo Molnar (mingo@pc5829.hil.siemens.co.at)
Thu, 18 Apr 1996 09:55:23 +0200 (MET DST)


On Thu, 18 Apr 1996, Ulrich Windl wrote:

> The easiest way to crash Linux is specifying more RAM than you have.
> What about a very quick and dirty test of the memory size
> (read-modify-read at the highest address)?

the very same issue was discussed half a year ago (this applies to almost
all other issues too :)), and Linus wrote that he doesnt want Linux
to probe high memory addresses, since the behaviour of a "wraparound", for
example, is undefined. (correct me if i quote wrong) The CPU pipeline
might get confused and executes the read earlier than the write, thus
confusing the probing code. This is only one problem. Memory mapped
devices might get confused too.

Anyways, the motherboard should report how much memory it has (Linux cant
look out and count the modules B), and if this interface is broken, then
complain to your motherboard vendor.

Linux has a workaround for this problem, you can specify how much memory
you have on the boot prompt or in your LILO options, but dont expect more
than this :(

-- mingo