Re: ZIP drive /Mac monitor ->IIGS?

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

<taibhse@csd.uwm.edu> wrote:

> Mournin'
>       Is there a video card that will allow me to hook up a non-IIGS monitor to
> the IIGS?

It might be possible to connect a very small selection of currently
available monitors directly to the IIgs, but I don't know of any
specific models.  The monitor would have to be able to support a
horizontal scan frequency of about 15 kHz (the same as NTSC television).
Most current multi-scan monitors do not handle frequencies lower than 30
kHz.  (This should not be confused with the vertical scan rate, which is
in the range of 50 Hz to 90 Hz.)


The only option for a video card is the "Second Sight" card, sold by
Sequential Systems.  It lets you connect a VGA or SVGA monitor to the
IIgs, which means you could also use some Mac monitors with an
appropriate adaptor.

The Second Sight works with most existing 8-bit and native IIgs
software.  As far as I know, it still doesn't work properly in double
hi-res graphics mode (used on the IIe, IIc and IIgs to produce
monochrome graphics at 560x192, or 16 colour graphics at 140x192).

Super hi-res graphics mode (IIgs specific) works fine, but some special
features are not available.  The areas that would cause most trouble are
"fill mode", mixing 640 and 320 horizontal resolution on the same
screen, and 3200-colour mode.  I don't have a Second Sight card, so I
haven't verified whether these features are supported - can anyone else
fill in the blanks?

The Second Sight can support higher resolutions and more colours than
the standard IIgs video output, but there is almost no software
available to take advantage of this.  (Fingers crossed, this should be
rectified in the near future.)

One of its main advantages is that its text mode characters look much
more solid than the standard IIgs ones, and it supports all the
capabilities of a PC with a VGA card, such as coloured text.  This
allows real ANSI display on a IIgs, rather than having to emulate it
using a relatively slow graphics mode.

(Note also that the Second Sight can be used with a IIgs RGB monitor,
but this monitor cannot support a vertical resolution higher than 200
pixels non-interlaced, or 400 pixels interlaced, so you don't gain as
much as you would with a SVGA monitor.)

>       Is there a way to format a ZIP disk in order to trick a IIGS into using it
> as a, albeit slow, hard disk?

There is no trickery involved, assuming you are talking about a SCSI ZIP
drive (there is no way to connect a parallel ZIP drive to the IIgs
unless someone works out how to connect it to an existing parallel card
or builds a PC-compatible card, and deciphers its communication
protocol).

I have connected my SCSI ZIP drive to the IIgs, and had no trouble
formatting a disk.  It holds three 32MB ProDOS partitions.  It is able
to act just like a hard drive, so you can boot off it.

You can also exchange data with a Mac by using HFS-formatted (Macintosh)
cartridges.  One problem is that the standard Iomega formatting software
on the Mac leaves some extra partitions on the disk which are not
recognised by the IIgs, and they cause an error to be reported when you
insert the cartridge.  You can just cancel the dialog box and use it
like an HFS hard drive.  It may be possible to avoid this by using some
other set of tools on the Mac to partition the cartridge.

Exchanging data with a PC is not easy, because the IIgs MS-DOS FST does
not recognise a PC-formatted ZIP cartridge.  The "MS-DOS Tools" package
might work with it, but I haven't tried.  The PC Transporter definitely
wouldn't work, because it doesn't support real PC hard drives, only
image files on ProDOS volumes.


Regarding SCSI cards: I've heard that the ZIP drive has been used
successfully with a RamFast card, and I used it with the Apple
High-Speed SCSI card.

I wouldn't recommend using it with an original Apple SCSI card under
ProDOS-8, because the firmware on that card is so old that it doesn't
know about removable SCSI hard drives, and you could destroy the
contents of a cartridge if you exchange one without rebooting (GS/OS
should be safe, as it doesn't use the firmware).

It should also be possible to use the ZIP drive on an enhanced IIe,
given a RamFast or Apple High-Speed SCSI card.


Regarding the speed of the ZIP: the SCSI version of the ZIP drive is
somewhat slower than modern hard drives, but certainly a vast
improvement over a floppy (even the parallel version I use at work is
noticeably faster than a floppy drive).

The main speed penalty compared to a hard drive is the seek time: it is
29 ms on average, compared to more like 10 ms for current fast hard
drives.  (However, several years ago hard drives had seek times in the
order of 80 ms or higher, so the ZIP is certainly faster than them.)

The maximum transfer rate is "60MB per minute" according to the box,
i.e. one megabyte per second.  Since this is the maximum speed that can
possibly be supported by a DMA device on an Apple IIgs, you aren't going
to lose anything there.  (On an enhanced IIe with an Apple High-speed
SCSI card, the maximum transfer rate is about 500 KB per second, so the
computer will be the bottleneck.)

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand