Re: GS question, anyone?

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <1995Feb8.184443.84888@kuhub.cc.ukans.edu>,
 <smtrimbl@kuhub.cc.ukans.edu> wrote:
> Okay, quick question:
> Beyond the 1meg upgrade, is there any way the ROM03 GS is 
> superior to the earlier ROM models?

Yes.  Much more of the toolbox is in ROM, and code runs faster in ROM
than it does in RAM (2.8 MHz vs about 2.6 MHz).  As a result, screen
updating via QuickDraw is noticeably faster on a ROM 3.

Other advantages of the ROM 3 (off the top of my head):

- Since there is 1 megabyte of fast RAM, you can have a total of 5
megabytes of DMA-compatible RAM (with a 4MB RAM card).  A ROM 1 can
only have 4 MB of DMA-compatible RAM.  Both machines are limited to 8
MB.

- The Apple 3.5 Drive device driver is much faster in the ROM 3 (this
will only affect ProDOS-8 programs, as GS/OS uses a driver loaded from
disk).

- The monitor firmware has Step and Trace commands, the disassembler
automatically tracks register size changes, and many of the commands
can cross bank boundaries.

- Hardware shadowing is provided for text page 2 (ROM 1 has to do it
in software, which slows the computer down quite a bit).  This isn't
very important - only a few old programs use text page 2.  (This is
the function of the "Alternate Display Mode" classic desk accessory.)

- AppleTalk firmware lives in slot 1 or 2 instead of slot 7, so
AppleTalk doesn't affect two slots.  Most of the AppleTalk protocols
are in ROM, which gives a slight speed improvement.

- Slot 4 can be set to "Your Card" and you can still use the mouse in
GS/OS programs (you still lose it in ProDOS-8 programs).  You lose the
mouse completely on a ROM 1 if slot 4 is set to "Your Card".

- More speed options for mouse tracking.

- All slots except 7 have the M2B0 (Mega II Bank 0) signal, allowing
the use of the Video Overlay Card and other video cards in most slots
(they are limited to slot 3 in the ROM 1).

- The sound circuitry is cleaned up somewhat, noticeably reducing
background noise.

- Keyboard Mouse and Sticky Keys are built into the ADB
microcontroller, so they work without any of the problems associated
with Easy Access on a ROM 1.

- An extended keyboard's Caps Lock light works without any software
support.  :-)

- Lower power consumption and less motherboard noise, which means
accelerators can run more reliably.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand