> craig wrote:
>
>
> I know PIII can support 64G physical memory. In FreeBSD how can I visit such
> range memory(4G-64G) ?
The short answer is "you can't".
The longer answer is that you end up having to window it using
segmentation; if you are familiar with the 4k window on video
memory in the TI 99/4A, or the bank select on the 6510 (e.g.
the ability to select between 32K of RAM, and 32K of ROM, but
not both at the same time, on the Commodore C-64 and the similar
arrangement on the C-128, etc.), then you;ll have an idea of how
the thing works... assuming you can find a motherboard that can
handle it.
This basically means that the memory is useless as a DMA target
or source for disk controllers or gigabit ethernet cards, and is
pretty useless for swap, if you ever have to copy from one section
to another (e.g. for IPC, SYSV shared memory, mmap'ed files, VM,
or buffer cache, etc.).
So for limited uses in data intensive applications, it might be
usable, but in general, it's nothing more than a hack so that
they can claim to "support" more than 4G, for some extremely
limited definition of "support".
But to directly answer your question: by rewriting much of the
low core virtual memory and page mapping handling code to know
about segmentation.
Have fun doing this, since by the time you are done, you will
probably be able to get IA64 machines for something less than
the $7000/unit that you have to pay today, and they will likely
have PCI/X, so you have enough bus bandwidth to actually make
the RAM halfway usable.
-- Terry
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message
