KNI (nee MMX-2) details (from comp.sys.intel):
----------
From: Erik Corry <erik@arbat.com>
Newsgroups: comp.sys.intel
Subject: Katmai/MMX2 details released
According to c't, Intel has released details of MMX2 in Katmai.
heise.de
(English link anyone?).
The Katmai has 8 128-bit MMX2 registers usable as 4x32bit
fp each. They are not aliased to the normal fp or MMX
registers. This is a correct decistion IMHO, would have
been better for MMX, too. It means the OS needs to know
about the extra registers, but upgrading your OS is no big
deal (if you are upgrading your processor), and if they do
it right, the application cannot tell that MMX2 is there
at all unless the OS activates the support, in which case
it is reasonable to expect the OS to also handle saving
and restoring the registers on context switches. (Not sure
whether W95 will support it. Seems beyond doubt that W98
will, as will Linux for both 2.0 and 2.1/2.2).
The advantage is that you can do MMX2 in parallel with
MMX or fp work, and it probably simplifies the internal
data paths.
Did AMD get this one wrong for 3D-Now?
There are conditional move commands, conversion functions
for MMX and FP, memory-streaming (cache control), distance
calculation and min-max commands.
----------
My comment: The new context-switching instructions were introduced in Deschutes (i.e. current PII) and are already used by Win98. |
