Re: Bogus low-memory mode
On Tue, May 28, 2013 at 08:54:00PM -0400, Donald Allen wrote:
> It also occurred to me to have a look at that upper memory limit that
> went by early as the install kernel was booting. It's 0xf6f0000 =
> 258932736. No wonder the installer is complaining.
Check your BIOS for any memory hole related option.
> Testing on different memory sizes isn't the issue. It's testing on as
> many different flavors of hardware out there that claim to be PCs.
> This G41 was made by IBM, not Lenovo, so came from where it all
> started. Linux, FreeBSD, OpenBSD, and NetBSD (and maybe Dragonfly --
Yeah well, despite it's the original company, it did undergo 20 years
of incremental changes with the requirement to keep old stuff for
compatibility. GNU Mach actually doesn't use the BIOS E820 memory map
provided by GRUB, only the E801-like lower/upper values as mentioned
in the multiboot specification : "The value returned for upper memory is
maximally the address of the first upper memory hole minus 1 megabyte."
It just happens that we didn't suffer from memory hole issues to make
the effort to fix that.
Also, considering GNU Mach currently only manages one contiguous block
of physical memory, and some drivers (Linux drivers mostly IIRC) assume
that, fixing it requires some work that may not be trivial.
See gnumach/i386/i386at/model_dep.c:mem_size_init for reference.
--
Richard Braun
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