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Re: [bug #17346] GNU mach can't handle 4GB memory


From: olafBuddenhagen
Subject: Re: [bug #17346] GNU mach can't handle 4GB memory
Date: Mon, 20 Nov 2006 15:14:02 +0100
User-agent: Mutt/1.5.13 (2006-08-11)

Hi,

On Mon, Nov 20, 2006 at 01:26:17PM +0100, Samuel Thibault wrote:
> olafBuddenhagen@gmx.net, le Mon 20 Nov 2006 12:16:41 +0100, a écrit :

> > 0x400000 translates to 1 GiB + 1 MiB.
> 
> Nope, it translates to 4GiB + 1MiB, which results to 1MiB (because of
> the 4GiB modulus).

Indeed, I mixed it up. That's because I discussed a slightly different
variant with Barry a few days ago. (In fact, your original comment also
talks about truncating to 1 GiB...)

> Maybe a safer algorithm would be to use
> 
>       vm_size_t memsize = 0x400 + boot_info.mem_upper;
>       
>       if (memsize >= 0x400000)
>               /* avoid overflow */
>               memsize = 0x400000-1;
>       
>       phys_last_addr = memsize * 0x400;

I like that.

-antrik-




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