Thanks for the Memories

Charles Curley charlescurley at charlescurley.com
Sun Nov 29 20:22:52 MST 2009


On Sun, 29 Nov 2009 16:30:30 -0700
Joe C <v2joecr at gmail.com> wrote:

> On Sun, Nov 29, 2009 at 4:14 PM, Charles Curley
> <charlescurley at charlescurley.com> wrote:
> 
> > Questions:
> >
> > * Where is the rest of my 4 GB? I paid good money for those 641MB!
> 
> My best guess is you are loosing memory to I/O address unless you are
> running the 64-bit version of the OS. I remember getting calls like
> that back when I did support for Dell with customers on the 32-bit
> versions of Windows XP. Like why is Windows saying that I only have
> 3.6 GB of RAM when I have 4 when I ordered it.

I was referring to the difference between the 4 GB the BIOS reported as
installed and the 3455 MB it says is "usable". Why is the missing 641
MB "unusable"? Looking at dmsg for 64 bit finnix, it looks like the
BIOS is reserving that much. What ever for? The 64 bit finnix reports
finding 3335 MB, which is close enough to what the BIOS reports as
"usable" that I won't quibble.

I had forgotten about memory mapped I/O, thanks for reminding me.
Clearly a 64 bit OS can put that wherever it wants (MMU permitting), but
the 32 bit OS has problems. That's a *lot* of I/O, though.

Gaakk, this brings back nightmares of the 286/386 days when you had to
play all sorts of games to use any more than 640 Kb.

> 
> > * Why the gap between the memory chunks? Not that it matters, Linux
> >  seems able to use them anyway.
> 
> My best guess is a 32 bit version of the OS was installed, sorry
> that's the only thing that I can think of.

Except that it was memtest86+ that reported them. OK, if memtest86+ is
a 32 bit app, that would explain that and why it tested in chunks even
if two were contiguous. Thanks.

> >
> > Any other thoughts?
> 
> Are you running a 32-bit or 64-bit version of Ubuntu?

The Ubuntu is 32 bit. It's a recent installation, with /home on its own
LV. I wonder if installing a 64 OS will be worth it, at least for
now.

-- 

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