Re: Varied IIgs Q's

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

Nathan Mates <nathan@visi.com> wrote:

> In article <338778f3.13043758@167.152.149.11>,
> Edhel Iaur, Esq. <LOSETHECAPITALWORDSedhel@bigfoot.com> wrote:
> >How many disk drives can you hook up to a IIgs, and where do they get
> >mapped to (slot/drive)?
> 
>    Off the disk port, up to 2 5.25" drives, and 2 3.5" (unidisks or
> Apple 3.5"s). More than that, and you'll probably blow the normal
> power supply. 5.25"s are mapped to S6D[12]; 3.5s go to S5D[12] first,
> then spill over to slot S3D2 (S3D1 sorta reserved for ProDOS's builtin
> /RAM disk using the second 64K of memory).

Corrections to the above: the /RAM volume goes in S3D2.  S3D1 is
normally unusued on a IIgs (some Apple IIe auxiliary RAM cards use it
for their larger ram disk).  Spillover from the Slot 5 SmartPort goes
into slot 2, provided there is no block device (e.g. disk controller,
RAM card, SCSI card) in slot 2.

If you are using ProDOS-8 2.0.1 or later, SmartPort volumes after the
first two may go to any unused slot, but will still use slot 2 first (if
it is available).

You can connect a maximum of four drives to the IIgs disk port.  They
can be any mix of 5.25" and 3.5" drives, but you are limited to two
5.25" drives and two Apple 3.5 drives.  You could have up to four
UniDisk 3.5 drives.  Also note that the drive connection order must be:
Apple 3.5 Drives, then UniDisk 3.5s, then 5.25" drives.

5.25" drives connected to the disk port are ignored by the SmartPort
firwmare (slot 5) - they are handled directly through the slot 6
firmware or IWM hardware (e.g. by the drivers built into ProDOS and DOS
3.3, or the AppleDisk5.25 driver under GS/OS).

> If you've got /RAM5 active, it's usually in S5D2 unless you're booting
> from it, when it drops to S5D1.

Useless trivia: /RAM5 is actually set to S5D1 (SmartPort device 1) when
the SmartPort firmware is initialized.  It is then swapped with device 2
if it is NOT the boot device.  :-)

You can also have a ROM disk attached to the SmartPort firmware.  This
requires a special memory card with a ROM disk header and driver at
memory location $F0/0000.  The ROM disk may contain up to 512K, using
banks $F0 through $F7.

I have an "OctoRAM ESP" card which provides static RAM in this area
which acts as a ROM disk (at least it would if the card had any RAM
installed - I borrowed it for another use several years ago).

With the RAM disk, ROM disk, and maximum of four SmartPort drives (two
Apple 3.5 and two UniDisk 3.5, one Apple 3.5 and three UniDisk 3.5, or
four UniDisk 3.5), the IIgs SmartPort may have up to six devices
connected.

In theory, you could also connect a SmartPort hard drive, which has its
own power supply.  This is likely to exceed the signal drive capability
of the computer, so should be avoided.

>    HDs and the like tend to spill over as much as possible elsewhere
> (RamFAST's control panel lets you select what drives go where) under
> ProDOS 8; under GS/OS, they're all available. GS/OS doesn't need
> "slots" and "drives" anymore; they're simply given a drive "number"
> and keeps around which drive # of which device driver is in charge of
> it.

The same goes for SmartPort devices, to a lesser extent: they are
accessed by slot number and 7-bit device number.

Someone could write an 8-bit operating system to make use of this.  The
two drive per slot limitation is a feature of ProDOS-8 (but it is so
tightly ingrained that it would be impossible to change without breaking
all ProDOS-8 applications).
 
> Much more logical and expandable; too bad they didn't do that
> earlier on Apple IIs. [I think the Apple III's OS had some nice stuff
> like that, but I could be mistaken.]

On the III, all devices are accessed by name, which is provided by the
driver (which is loaded from disk).  SOS's device architecture is quite
similar to GS/OS - I think Apple actually used SOS as the basis for many
features of GS/OS.

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