26 Jan
2010
26 Jan
'10
11:02 a.m.
It was definitely in the 1541, I remember it distinctly,
all sorts of interesting tricks came out of it.
all part of "inside commodore dos" book, still have the original.
but still, that sort of trick isn't seen today.
even the manufacturers of cpus have bought into the "faster mhz is better"
trick,
rather than multiprocessing.
thus the death of the c64, the amiga, and ppc-mac... sigh.
(one could add the vax to this list and ppc sun as well I suppose)
thus explains why my amiga-1200 always felt "faster" than my pentium4.
you had custom chipsets for dedicated tasks, a multiprocessing cpu
whereas on the pc, it was one doing everything.
uh oh i feel another religious war coming on...
Dan.
Date: Tue, 26 Jan 2010 13:54:06 -0500
Subject: Re: General religious wars (was Re: Editor religious wars)
From: ethan.dicks at gmail.com
To: cctalk at classiccmp.org
On 1/26/10, Dan Gahlinger <dgahling at hotmail.com> wrote:
_________________________________________________________________
Reinvent how you stay in touch with the new Windows Live Messenger.
http://go.microsoft.com/?linkid=9706116
I keep thinking it was the 6520 or 6522 processor
in the 1541
which had the cool dual-clock ability.
1/2 a clock running as one mode, the other 1/2 as another mode,
technically running two instructions at once. so to speak.
The 6520 and 6522 are the PIA and VIA, respectively - parallel I/O and
timers, not processors.
There were tricks one could perform with the 6502 since it had
alternating fetch and execute cycles, so by doing something else with
the bus during the right portion of the clock phase, you could design
a board to "do twice as much" at 1Mhz, but I don't think the 1541 did
that.
It did have a pair of "processes" in its firmware - one to talk to the
host and parse DOS commands, and one to perform low-level "tasks"
(move the heads, read/write buffers, etc).
-ethan