Sender: jur AT rz DOT hu-berlin DOT de
Message-ID: <37458AD6.F3DA19D1@informatik.hu-berlin.de>
Date: Fri, 21 May 1999 16:33:26 +0000
From: Jens-Uwe Rumstich <rumstich AT informatik DOT hu-berlin DOT de>
Organization: TUSCON
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To: pgcc AT delorie DOT com
Subject: Re: K7 potentials
References: <374331C4 DOT CA20644C AT lycosmail DOT com> <374515C1 DOT A9DDD353 AT informatik DOT hu-berlin DOT de> <19990521151041 DOT I2804 AT cerebro DOT laendle>
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Reply-To: pgcc AT delorie DOT com

Hi!

> > It would break the x86-compatibility. The x86 only has 3 bit for the
> > registers, so you canīt have more than 8 registers without heavy
> > changes in the instruction set :-(
> 
> No, it wouldn't. The ppro has much more than 8 registers through register
> renaming. Under this light having only three bits for the register might
> even improve performance due to better packed instructions.

Of course I know, that most modern x86-CPUs have hidden registers, but
IMHO
its still a difference compared with having direct access to these
registers.
If you have more variables than registers, than you have to store these 
variables in memory, which is more expensive (load+alu instead of alu
only),
even if stored in fast cache. And additionally its probably quite hard
for
parallelism to have only 8 independend registers but perhaps 8 or even
more
integer execution units and be forced to avoid dependencies. The hidden 
registers help a bit, but more freely accessible register would be much 
better IMHO :-)

> (No kidding, I expect compressed assembly in the next years, x86 already
> comes close!)

Isnīt EPIC pretty close to this? I heard, there are 3 instructions in
one
128bit value. It would come even closer to compressed assembly IMHO :-)

> > the start of the second fab in Dresden.
> 
> Oh, thats great!

AMD plans to start Dresden in Q3/99 with 0.18 alumunium and convert to
0.18
copper in Q1/2000 allready :-)
Dresden is intended to produce K7 only, so the number of produced K7
should
rise quite fast :-)

>       ---==---(_)__  __ ____  __       Marc Lehmann      +--

cu
	Jens-Uwe