Sender:	nate AT cartsys DOT com
Message-ID:	<3665D4D9.8A24AEB@cartsys.com>
Date:	Wed, 02 Dec 1998 16:01:29 -0800
From:	Nate Eldredge <nate AT cartsys DOT com>
X-Mailer:	Mozilla 4.05 [en] (X11; I; Linux 2.0.35 i486)
MIME-Version:	1.0
To:	djgpp AT delorie DOT com
Subject:	Re: which is the fastest way to clear the screen i mode13h?
References:	<199812011754 DOT RAA25002 AT remus DOT clara DOT net>
Reply-To:	djgpp AT delorie DOT com

Arthur wrote:
> 
> Does PC ASM have a MOVEM command? On the M68k MOVEM shoved the contents of
> any or all (of 16) 32-bit registers to an area of memory. One technique was
> to clear as many registers as possible, and dump the contents to the screen.
> If you could clear as many as 15 registers, then that would be a whole 60
> bytes cleared in the same number of cycles as it would take about 5 move.l
> instructions (32-bit move).
> 
> Is this not possible on the PC? It seems like a very basic command to me.

Nope.  Closest thing is PUSHA, which pushes all the registers to the
stack.  Since the stack pointer is one of the registers so pushed, I
don't think you could use this to fill arbitrary blocks of memory.  It's
not so fast either; it took 18 cycles on a 386, and probably not many
less on newer chips.  We're stuck with the "string" instructions.

The 386 is not the best possible architecture, granted.  8
"general-purpose" registers, one or two of which are reserved... really
now.  Let's hope Intel will get it right with Merced.
-- 

Nate Eldredge
nate AT cartsys DOT com

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