From: breck@ganzer.ecs.umass.edu ()
Subject: Re: Information on: The IIvi, IIvx, and Performa 600
Originator: breck@kirk.ecs.umass.edu
Organization: University of Massachusetts, Amherst
Date: Sun, 16 Aug 1992 21:00:17 GMT

Someone emailed to me (Liam Breck):
> in comp.sys.mac.misc you write:
> > The IIsi's only advantages are slightly better CPU speed (not a big
> > enough difference to notice in real time use, but you will notice the
> > disappointing screen redraw speed) and the ability to plug in Nubus
> > cards, again, not an issue because the LCII is a very popular machine,
> > so there are a lot of cards for its PDS (processor direct slot).
>
> You want to justify this? The si uses a 32 bit bus, not a 16 bit bus, so is
> about twice as fast. Same reason an SE/30 is twice as fast as an LCII. Also
> an LCII has max memory of 10MB. That doesn't leave much room for expansion.
> I have 8MB on my SE/30 right now and plan to go to 20MB in a month or so.
> I'd be pissed off if my machine maxed out at 10MB.

This is a common misconception.  Actually, the IIsi is about 28%
faster, which is not enough to notice in most real-time applications.
When doing something very CPU-bound, you might notice.  That is to
say, if you usually complete a coffee break while compressing a large
archive with an LCII, you will have a bite of doughnut and sip of
coffee to go when the same task finishes on a IIsi.  :-) This 28%
difference in speed is mostly accounted for by the difference in
processor speed beetween the two machines -- 16MHz vs. 25MHz.  The
*IIci* is something like twice as fast as the LCII since it's clock
speed is 33MHz.  The bandwidth of the memory bus is really not
critical in personal computers, 'cause other bottlenecks hold things
up before the bus width does.  For instance, the 80386 is only 4%
faster than the 80386sx, which has a 16-bit external memory path.
It's the same in the case of the Macs; you'll find that the original
Mac II is only 4% faster than the original LC (both 020s at 16MHz).

A really critical issue, though, is screen redraw time, since most
real-time apps (word processors, drawing apps, the finder, etc.)
redraw the screen a lot.  The LCII uses the latest Apple on-board
video standard, which includes dedicated, dual-ported VRAM.  The same
stuff that the Quadras use, only pared down for the LCII.  It's very
fast compared to using the main memory for video (the IIsi and IIci do
this).  You can speed up video on the latter machines by making your
RAM cache huge, but that's another subject, see one of the columns in
the current MacWorld (sorry, forget which one) for more info.

Another point about video...  Since the LCII can use a low cost VGA
monitor (I got a Trinitron screen for $350) it really lets you save on
the monitor.  To get the same quality on a IIsi, expect to shell out
the bucks!

The 10MB limit on the LCII's memory expansion is unfortunate, but not
unacceptable.  I have 8MB in mine, and run a whole heap of concurrent
applications and I haven't run out of memory yet!  If I was going to
use Quark and Photoshop at the same time to work on some layout, I
would buy a IIci (or one of the future Macs) and a lot of memory, not
a IIsi and same.

So, when the whole story's told, the LCII is a better machine
price/performance wise than the IIsi.  The only reason I can think of
to buy a IIsi is if you absolutely have to use a Nubus card.  But
since the LC(II) is the best selling Mac ever made, I don't expect
you'll find a lack of cards for it...
-- 
Liam Breck     breck@zonker.ecs.umass.edu