Re: [Devil-Linux-discuss] i485, i586, i685 ?

[Bryan J. S. <the...@ya...>]

Goldorak <kol...@ya...> wrote:
> Hello,
> I am using devil linux version i485, on a Pentium 4, i
> am abit confuse about version i585 and i685... SMP and
> server.

I assume you mean i486, i586 and i686.  They are common Instruction
Set Architecture (ISA) nomenclature.  Here's the general concepts ...

i486 adds several requirements at the CPU ISA, including the
Translation Look-aside Buffer.  It has been a long, long, long time
(circa 1994) since a processor design wasn't fully i486 ISA
compatible.  This includes countless "embedded" processors.

i586 is actually, and quite not well proliferated, a bastard.  It is
really designed _only_ for Intel branded, true, _original_ (not
Pentium Pro, II, etc...) Pentium processors.  Although it will run on
a majority of processors, a number of optimizations and approaches
are not ideal for newer processors.

i686 is pretty much the kernel you always want to run on any recent
hardware circa 1999+.  In kernel 2.6, most optimizations are
dynamically loaded for different processors (i.e., there is no
separate Athlon optimizations in kernel 2.6, they are in the i686
build).

In the overwhelming majority of cases, processors are best on i686
or, if they are not fully i686 compatible (e.g., original Cyrix 6x86,
possibly M2 as well), i486.  You typically never want to run the i586
built binary/kernel except on true, original Pentium processors --
not latter Pentium Pro, II, etc... processors.  I.e., in some cases,
you'd be better off running a i486 kernel on many i686 ISA compatible
processors than a i586 (because of the hacks required for Intel's
first generation, superscalar design that were subsequently address
in the i686/Pentium Pro on-ward).

That's just "a general overview."

There are various modifications to how i686 works, including 36-bit
(64GiB) Processor Address Extensions (PAE) that allow more than 4GiB
(3GiB user) memory addressing that servers typically use (at a
performance hit in overhead, especially for non-AMD processors
without an on-chip I/O MMU -- long story).  There are also
multiprocessor (MP) scheduling considerations for i686 kernels.


-- 
Bryan J. Smith   Professional, Technical Annoyance
b.j...@ie...    http://thebs413.blogspot.com
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