Re: Apple IIGS Questions

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

In article <9MAY199417392203@acad3.alaska.edu>,
Mr. Spock <faso101@acad3.alaska.edu> wrote:
> 
> 	I have some GS questions for you guys, as I'm considering getting one.
>
> 1. Is is true that the later ROM versions of the GS provide better
> compatibility with old Apple II software (I'm mostly interested in
> the games)

News to me.  The only signficant item I can think of is that the ROM 3
IIgs has a proper implementation of the second 40-column text screen
(i.e. it supports shadowing in the $00/0800-0BFF area).

ROM 1 emulates it by rapidly copying this area of memory into bank $E0
if you turn on the "Alternate Display Mode" in the classic desk
accessories menu.  This won't work with programs that lock out
interrupts, and it slows the computer down quite a lot!

ROM 3's "Alternate Display Mode" simply enables the appropriate bit in
the shadow register.

This is a rather minor feature - I've only encountered one program
which uses the second text screen.

Other than that, I'm not aware of any specific improvements in
compatibility with old software.

> I had a ROM01 GS and it had pretty poor compatibility with most of
> the games I had. Will the current version of system software provide
> better compatility and allow me to launch DOS 3.3 and old Prodos
> software directly from the finder? 

You've always been able to launch ProDOS-8 SYS files from Finder - it
just launches ProDOS-8, which runs the appropriate applications.
Whether you can get back to Finder again is a different matter.

Define "old ProDOS software".

The system software doesn't provide any way to launch DOS 3.3
programs, but there is a shareware program called "DOS 3.3 Launcher"
which lets you set up DOS 3.3 disk images on your hard drive, which
can be launched from Finder or any other program launcher which
supports launching applications with a specified document.  I don't
think this can handle copy-protected programs, though.

The latest version of the system software (6.0.1) includes a file
system translator which allows you to copy files from DOS 3.3 disks,
but that is all it can do with them.  (The DOS 3.3 FST was introduced
in System 6.0).  6.0 and 6.0.1 also have an HFS file system
translator, which can copy files to or from a Macintosh HFS disk.

> 2. Does the Apple IIGS use Direct Memory Access for any subsystem
> (SCSI, floppy, serial ports, etc)? Does it contain any supporting or
> coprocessing chips? Are these made use of by current system software?

The two most popular SCSI cards (RamFAST and Apple High-Speed) can
optionally use DMA.  A few devices aren't DMA compatible (particularly
older memory cards, but the RAMFast claims to get around this problem)
so you may have to disable DMA on the SCSI card if you have one of
these devices.

Nothing else uses DMA _into_ the IIgs memory, but you could regard the
video system as using DMA to get data out of the IIgs memory.  :-)

The Apple slot bus supports DMA (as evidenced by the SCSI cards) but
is rather limited - only one device can use it at a time, and there
are timing restrictions.

The IIgs has further problems with DMA.  Since the IIgs inherited its
slot bus from the IIe, there is no direct way to support 24-bit memory
addresses.  To get around this, the IIgs has a "DMA Bank Register",
which provides the upper 8 bits of the address for any DMA access.

This design basically limits you to one active DMA source at a time.
It prevents the use of "background DMA", such as might be used with a
serial port.  Disk I/O cards can use DMA, because they are polled by
the computer and only one can be active at a time.

There are probably other DMA devices, e.g. the "Bluedisk" controller
(which supports MFM drives up to 2.88MB).


Regarding coprocessor chips: not as such.  The Ensoniq Digital
Oscillator Chip is basically a separate processor, with its own 64k
area of memory (which can be written to by the IIgs).  There is also
the Apple Desktop Bus controller, which is a single chip computer with
a Mitsubishi processor based on the 6502.  It is responsible for
polling the mouse, keyboard and other Apple Desktop Bus devices.

There have been a couple of cards which provide floating point
co-processors, but they are accessed as peripherals rather than as
extensions to the main processor.

Several I/O cards contain their own processor (e.g. Apple's SuperDrive
controller, and the RamFAST SCSI cards) but access to these is usually
tightly controlled by the card design.

> 3. What are the advantages of the TransWarp GS over the ZipChip? What other
> acceleration options do I have? Where can I get these accelerators and how
> much?

The TransWarp tends to be more reliable in noisy computers, since it
is a high power design.  This makes it a much better heater than the
ZIP GS.  ;-)

There are major disadvantages, in particular the company that made them
is no longer in business.

There are no accelerators for the IIgs other than the TransWarp GS and
the ZIP GS.

You can get the ZIP GS from many mail order sources (Quality Computers,
Resource Central, LRO Computer Sales, Alltech Electronics) or
directly from ZIP Technology.  Price is somewhat variable.  You need
to decide what processor speed (7 MHz, 8 MHz, 9 MHz, possibly 10 MHz)
and cache RAM size you want (8k, 16k, 32k, 64k).  If you want to get
your ZIP going really fast, you may be best off buying a slower one
and replacing the processor, crystal and cache RAM yourself.

See the TransWarp/ZIP FAQ, which is posted occasionally to this group
by Frank Lin (fmlin@netcom.com).

The TransWarp GS may be available from some of these sources (LRO
used to sell them but it isn't listed in their latest advertisements).


I don't have a current price list for Quality Computers, but their
telephone number is 810-774-7200 or 800-777-3642 (Orders Only).  In
their July 1993 advertisement in Incider/A+, they quoted a ZIP GS 8
MHz/16k at $199.95.

Resource Central sells a ZIP GS 8 MHz/16k for $199.95.  Ph 913-469-6502. 

Alltech Electronics sells a ZIP GS 7MHz/32k for $159.00.  Ph 619-721-7733
or 800-995-7773 (orders only).

LRO offer various speeds: 7MHz/8k $139, 8MHz/16k $174, 9MHz/32k $235,
10MHz/64k $379.  Their number is 815-338-8658 (international) or
800-275-4576 (orders only).  I'd hesitate to recommend LRO, because
many people have had problems with them.

I don't have current prices if you order directly from ZIP Technology,
but they are likely to be higher than the above.  Their number is
310-568-2002.

E-Mail me if you need fax numbers or addresses.

> 4. Is it possible to connect a GS (through Appletalk) to my mac and copy and
> use software from my GS disks from the hard drive of my mac?

Yes.  There are basically two options:

1. Set up your Macintosh as an AppleShare file server.  This requires
the AppleShare software, which is rather expensive.  AppleShare 2.0
requires System 6 on the Mac, and takes over the whole machine.
AppleShare 3.0 requires System 7 on the Mac, and other programs can be
used at the same time (under MultiFinder).

2. Use "Personal File Sharing", which is provided by System 7 on the
Mac.  This is very easy to set up (I've done it twice and have yet to
see any documentation on it).  I suspect it is slower than a dedicated
file server.  You can share any hard drive on your Mac, plus CD-ROM
drives.

The main advantages that AppleShare has over Personal File Shareing
are:

(a) You can boot a IIe or IIgs from an AppleShare file server, but not
from a Mac running Personal File Sharing.

(b) You can have a lot more users on an AppleShare server.

Otherwise, the IIgs can't tell the difference.


I have a small AppleTalk (LocalTalk) network set up with my two
IIgses, ImageWriter II, and a Mac Plus I've borrowed from a friend.
It isn't exactly fast - you'll probably want a more powerful Mac if
you intend to make serious use of it as a file server.

The network is also rather slow.  It is comparable to a floppy disk in
terms of file transfer speed.


It is easiest to set up the IIgs if you have a hard drive on it.  With
System 6 or 6.0.1, you can set up a locally booting system with file
server access in about 1400k, so it will fit on a SuperDrive, but not
on an 800k system disk.  If you trimmed it way down and didn't use
Finder on the system disk, you can just get a boot disk which lets you
log onto the file server.

You might be able to get a little more onto a floppy boot disk if you
used System 5.0.4.  I'm not sure which version of the IIgs system
software was first to support AppleShare (probably 3.1).  System 4.0
(the original release of GS/OS) doesn't support AppleShare, but 5.0
and later are fine.


My main IIgs has a hard drive, so I just log onto the server when I
want to transfer files.  The second IIgs has no hard drive, so I've
set up a 1600k /RAM5 volume with the necessary software.  This
computer is used mainly for communications, and I never turn it off.
I've taken a copy of the installed system software on a couple of
floppies, so I have a quick re-installation procedure if necessary.

The second IIgs downloads files from a ProDOS-8 communications program
directly to the Mac's hard drive, and when the transfer is comlete, I
can just copy it to the hard drive on my main IIgs.


Note that you cannot use a IIgs as a file server (though this is
something I would like to look into writing at some stage) - you need
a Macintosh if you want to use an AppleTalk network for anything more
than printing (unless you're writing your own software which uses the
network protocols directly).
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand