Re: tlug: Linux news

["Stephen J. Turnbull" <turnbull@example.com>]

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tlug note from "Stephen J. Turnbull" <turnbull@example.com>
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>>>>> "Jim" == Jim Schweizer <schweiz@example.com> writes:

    Jim> Is there a 64 bit Linux available for the Intel platform? I
    Jim> haven't heard of it...

Nope.  As far as I know, there *isn't* a 64-bit Intel platform (but
I'm real fuzzy on the 860 series).  The Pentium does memory transfers
on a 64-bit bus, and if you build with "Pentium" as the target
platform optimizations for that bus will be done (to the extent that
GCC does them, and there may be a few hacks in the kernel code).

However, all peripherals run on the 32-bit wide PCI bus as far as I
know.

Also, it's not clear to me what "64-bit OS" means.  32-bit was
important, because 16-bit address spaces are not big enough for modern 
software, and 16-bit color falls somewhat short of true color.

This is not true for the jump between 32 and 64 bits.  It's clear that
in the medium term there will be systems that start to feel
constrained by a 4GB address space, but for practical purposes the
32-bit linear address space for memory and 32-bit color space for
video (and note that a 4096x4096 screen even at 32-bit color "only"
takes up 64MB, so GUI considerations seem unlikely to use up
gigamemory memory until we get 3D displays) are about as much as you
could possibly need at the moment.  Of course there are optimizations
that can be done, and computations will be faster.  But it seems to me
that from the point of view of kernel development RISCiness and
instruction sets are much more important issues.

An article that bears on these issues is in the Jan 1997
Communications of the ACM, on Intel's "MMX" technology (the multimedia
instruction set that will be built into future iAPX processors).  It's
quite clear from that article that from the multimedia standpoint the
bandwidth advantages of a 64-bit bus require a lot of algorithmic
tuning; I feel that 64-bit-ness does not really change the way system
programming is done.

Steve
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