Re: how to tell linux (on x86) to ignore 1M or memory

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 06/22/2007 03:46 AM, H. Peter Anvin wrote:

Rene Herman wrote:
On 04/19/2007 04:18 PM, Bart Trojanowski wrote:

I need to preserve some state from the bios before entering protected
mode.  For now I want to copy it into some ram accessible by
real-mode, say the last megabyte visible in real-mode.

What's the easiest way to have linux ignore the megabyte starting at 15M?
Note that real-mode can only access the first megabyte (*) and not the
first 16. 16MB is the 16-bit protected mode (286) limit.


No, 16-bit protected mode (on 386+) is not limited to 16 MB.

That all depends on one's definition of 16-bit protected mode. The "(286)" after mine meant I was talking about the definition in which descriptors have a 24-bit base (and 16-bit limit) field -- ie, real 286 and arguably, "real 16-bit protected mode".

Yes, I guess another valid definition is "code with a 16-bit address and operand size default" on a 386+ and sure, that's just flipping a bit away. In the context of Linux I agree it's also a sensible definition, so, well, whatever. The point was that real mode could only access the first 1M, not the first 16... :-)

Rene.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux