Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!applix!scotte
From: scotte@applix.com (Scott Evernden)
Newsgroups: comp.unix.amiga
Subject: Re: second thoughts on buying a 3000UX
Message-ID: <1152@applix.com>
Date: 12 Mar 91 03:42:54 GMT
References: <61751@masscomp.westford.ccur.com> <1135@applix.com> <5PR9W6D@xds13.ferranti.com> <1145@applix.com> <19754@cbmvax.commodore.com>
Reply-To: scotte@applix.UUCP (Scott Evernden)
Organization: APPLiX Inc., WestboroMA
Lines: 47

In article <19754@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>
>When it comes to moving windows under X, blitter speed is probably not the
>issue.  While the blitter does process at the equivalent of a 14.3MHz ISA
>bus, the main point of X on an A3000UX would be that the CPU has a 32 bit
>path to a 7.16MHz that runs with no wait states (at least in the monochrome
>X that programmer's use).  Regardless of the video mode, the typical VGA card
>takes 20-30 wait states per access, ...

Well, this just isn't true these days.  It might almost be true if you've
always got the VGA-mode rotate registers set.  Why would anyone use such a
VGA for X if they didn't have to?  ET4000 VGA cards, for example, can run
with no wait states.  Aside from a co-p., they are the only sensible thing
to put on an ISA bus.  So, an end to this VGA wait state rumor, okay?

And, about this 32bit CPU access to chip memory- I would be very suprised
to find the low level graphics and blit routines making thorough use of
this capability.  Generally, you read 16 bits, shift 32, and write 16, etc.

>...  and if you stick to original VGA compatible
>operations, you're stuck at 8 bits per access, whether on an ISA/AT or XT bus.

With original VGA compatible operations (4 planes), that 8 bits per access
is modifying 8 color pixels (32 bits) all at once.  The Amiga blitter needs
to write to 4 bytes to achieve the same effect.  Also, even for simple
operations like filling an area, the blitter eats cycles and is not producing
destination bytes on every clock.   But the blitter is not the issue...

>Of course, X on a PC vs. X on an Amiga is a fair test.  Windows on a PC vs.
>Intuition on an Amiga is so skewed in the Amiga's favor, if you have any decent
>comparative performance on the PC setup, you're extremely lucky, and you paid
>for it.

Windows vs. Intuition:  You're right, I've never denied this.  The original
question had nothing to do with Windows or Intuition.  It was, "If I throw
AmigaDOS away, how compelling are the reasons to get the A3000UX for UNIX
software development."  In my case, I was able to arrive at a substantially
more powerful solution by going with a 486/33, for nearly the same money.
Arguments about 32bits at 7.16MHz vs 16bits at 12MHz, and my wait states
are fewer than yours, and blah blah blah are silly and haven't caused me to
think any differently.  Bottom line, I work radically faster in my daily
edit-compile-go grind than I would on a 3000.  Period.

The Amiga is great at the doing the stuff it was born to do.  And it also
happens to do a nice job as a UNIX application box, too...

-scott