Re: why linux can't see my memory
On 06/01/14 13:14, Miles Fidelman wrote:
> If you have a memory hole, chances are there wouldn't be a BIOS option
> to help. It has to do with the way that memory-mapped i/o is handled
> with some families of chips and their associated motherboards.
>
> For example, I have two older servers - fully loaded with 4Gig of RAM
> (as I said, older servers) - but no way, no how does the system see more
> than 3G. The other 1G is taken up by memory mapped i/o space. It's a
> hardware design issue, not a BIOS issue. (For reference: P4 640
> processor, Supermicro P8SCT motherboard).
>
> In addition to the reference I sent earlier, this sort of describes the
> issue: http://en.wikipedia.org/wiki/3_GB_barrier
> and this: http://www.dansdata.com/askdan00015.htm
> If you do some googling, you'll also find an Intel design note that's
> the definitive description of the issue (I can't seem to find it right now)
>
> Some BIOSs support "memory hole remapping," but others don't - and that
> assumes the underlying chipset and motherboard will support it. A lot
> don't.
shadowing(??)
>
> Of course this might not be the problem you're seeing. What CPU,
> chipset, motherboard, and BIOS are you running?
dmidecode will give you the information Miles (and others) need if you
can get a Live CD to boot.
Most of the Debian/Debian-based ones will take the kernel parameter
"mem=$amountM" as mentioned elsewhere in this thread (where $amount is
megabytes found during POST and "M" must be upper-case)
e.g. for Knoppix:-
knoppix mem=1024M (gives W.I.M.P. requires minimum of 120MB of RAM)
or:-
knoppix 2 mem=1024M (gives you runlevel 2, text-mode, single-user root,
runs in <50MB RAM)
dmidecode needs to be run by root, it's output is lengthy so best post
it to a pastebin and link to it in your post.
If you use Knoppix in run-level 2 you can setup networking with:-
knoppix-networkmanager
Email the dmidecode report to yourself (as root):-
dmidecode | mail longwind2009@gmail.com -s "dmidecode report"
Also - check your BIOS to see how much RAM is being allocated to the
built-in video card (aperture is different and doesn't rob the system of
RAM).
>
> Long Wind wrote:
<snipped>
Kind regards
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