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01.013 What is an Apple II: The Apple IIgs


This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.

01.013 What is an Apple II: The Apple IIgs

         The IIgs (or "GS") represents a giant leap in the Apple II line.  It's
65C816 microprocessor can switch to 6502-emulation  mode for running 8-bit
Apple II software favorites, while, in native mode, it runs 16-bit GS
applications. GS delivers  new super-hires graphics modes, a toolbox in ROM, a
32-oscillator Ensoniq sound chip, and a max base speed of 2.8MHz. Base RAM
memory is 256kB (ROM-01) or 1MB (ROM 3) expandable up to 8MB.

     GS built-ins include modem and printer serial ports good for up to 230k
baud, Disk Port supporting two 5.25" and two 3.5" (800k) drives, RGB and
composite video outputs, enhanced and 'old Apple' sound, ADB bus for keyboard
and mouse, game port supporting two two-button joysticks, clock/calendar, and
battery RAM to retain user settings accessible via the Control Panel. (To get
to the Control Panel press OpenApple-Control-Escape and select "Control
Panel".) There is more about Apple IIgs specifications

in the FAQs resource file R024GSSPECS.txt.

     The IIgs can run DOS 3.3, ProDOS, Pascal, and any other OS the earlier 8-
bit models can run. In 8-bit or "emulation" mode, it works much like an
enhanced //e, even down to supporting nearly all of the old monitor routines
and softswitches. One notable difference is that users must go to 64k Bank $FF
(e.g. FF/F800 - FF/FFFF) to view monitor ROM contents. In the default (Bank
$00) area, an F800L etc. monitor command shows code in the "Language Card" RAM.
Like the //c series, it does not support the ori

ginal Apple casette tape I/O.

     GS is the only A2 machine which can run GS/OS. GS/OS and Toolbox routines
make it possible for the System Finder program to deliver a sophisticated
'mouse and windows' environment which looks very much like PC's Windows. The
current version of System is System 6.0.1.

     The first GS's were released in the Fall of 1986. The batches produced
until mid-late 1987 became known as "ROM 00" machines after release of the "ROM
01" models. When you turn ON or force restart a ROM-01 GS, the startup screen
shows "ROM Version 01"; on a ROM-00 GS the startup screen says nothing about
ROM version. (Press OpenApple-Control-Reset to do a forced restart.)

     The original GS's came in cases marked "Limited Edition" with Steve
Wozniak's signature. Often, these are referred to as "Woz GS's". (See FAQs
resource file R002WOZGS.GIF for a picture.) Only about 50,000 ROM-00 IIgs's had
the "Woz" signature. A relatively small number of users chose Apple's option to
upgrade their //e's with a motherboard swap. Introduced in early 1987, the
upgrade included "IIgs" labels which users could substitute for "//e" in the
case insert.

     At the time of the ROM-01 change-over in 1987, Apple supplied a ROM-00-
to-ROM-01 upgrade service free. It consists of swapping in a new ROM and a new
Video Graphics Controller ("VGC") IC. ROM-00 machines which have not had the
upgrade can not run modern GS software-- the ROM must be upgraded. Alltech
(760-724-2404; http://allelec.com ) is a good place to check for a ROM-01
'upgrade kit' consisting of the 01 ROM. (Price: around $30.00)

     The VGC upgrade is not required for software compatibility, and is not
needed for all machines anyway. It is supposed to fix cosmetic problems in
monochrome double-hires graphics mode (pink flickering or fringing on what is
supposed to be a black and white screen).  On some machines the VGC swap also
fixes some color combination problems in 80-column text mode.

Note: ROM-00 machines can boot disks which start System up through Version 3.
(Booting these disks typically starts by displaying some version of "ProDOS
16".) The downside, of course, is being unable to boot modern versions of
System and use software which needs to run under the later versions. On the
other hand, a number of very early products run under versions of System which
have no patches for ROM-01 or ROM 3. Original diskettes for these products will
boot correctly only on a ROM-00 GS.

     Whether via the upgrade or original purchase of a newer GS, by late 1987
nearly all GS users were 'on the same page'. That is, we had the ROM-01
platform with its base 256kB RAM plus the official Apple 1MB Expansion Memory
Board plugged into the Memory Expansion Slot for a total of 1.25MB of fully-
accessible system RAM. For the next couple of years, practically all GS
software was designed to launch from 3.5" diskette under "ProDOS-16" and to fit
within the 1.25MB of RAM everyone was assumed to have


     In 1989 Apple introduced the "ROM 3" GS-- the startup screen shows "ROM
Version 3". (No ROM-02 GS was ever released). The only major improvement over
ROM-01 is more base RAM-- you get 1MB instead of 256kB. This is a very nice
benefit. It means that a ROM 3 with a 4MB Mem Exp Board will have 5MB of fully
accessible RAM whereas a ROM-01 can have 4.25MB of fully-accessible RAM. In
effect, the ROM 3 owner gets a 'free' 800kB RAM disk.

     As Mitch Spector notes in his listing of ROM 3 features (in the "Hardware
Hacking" FAQs), the newer GS offers a number of other nice pluses with the only
significant minus being incompatibility with a few older GS programs and pre-
System 5 versions of GS System. Chiefly, ROM 3 is a 1989 re- do of ROM-01
featuring more streamlined hardware and more built-in firmware.

     Since System 5, booting GS System applies in-RAM patches matched to ROM
version 1 or 3. The patches, located in System/System.Setup/, are TS2 for ROM-
01 and TS3 for ROM 3. This achieves nearly identical operation.

     Very few ROM-01 owners felt any urge to move to ROM 3. Even today, the
vast majority of installed GS's are ROM-01 machines.

     The 1990's saw wide adoption of four major GS enhancements:

OS- After years of foot-dragging, Apple finally produced a decent 16-bit GS
operating system with release of System 5.0. Within a few years this evolved
into today's System 6 (System 6.0.1). System 6 has won wide acceptance as a
relatively stable OS which, at last, allows GS users to access many of the
features of GS computing promised back in 1986. Although any ROM-01 or ROM 3
IIgs with at least the 1MB Apple Expansion Memory card installed can boot a
fairly decent install of System 6 from diskette, the f

act that it is likely to use at least 800kB of RAM somewhat limits the
applications which can be run, especially on the ROM-01 GS.

Memory- Driven, in part, by the need for more memory to run System 6, 4MB
became the standard size of installed Memory Expansions. Except for school GS's
and GS's taken out of circulation and tucked away in closets, the old Apple 1MB
Expansion Boards have long ago been replaced with boards adding 4MB- 8MB.

Hard Disk- As with memory, the size of newer versions of System supplied a
strong push toward adding a hard disk. Software was becoming larger, too, and
there was so much of it that making everything work from diskette became
impossibly cumbersome. Lower HD prices, attractive SCSI interfaces such as
RamFAST, and low-cost, easy single-card IDE solutions such as the Focus "Hard
Card" and SHH Systeme "Turbo" cards have helped make the hard disk a standard,
expected peripheral on today's GS.

Acceleration- Few commercial software offerings actually sought to push GS
users to higher speeds; and, as a result, users went for years feeling no great
need for Applied Engineering's expensive Transwarp accelerator. The arrival of
Zip Technology's lower-cost ZipGS board together with a clear need for more
speed to handle System 6 sparked a nearly overnight 'acceleration revolution'.
Today, an accelerator running at 8MHz or better is considered, very nearly, to
be a necessary IIgs enhancement.

Recommended configuration: ROM-01 or ROM 3 with 4MB or 8MB Memory Expansion
board-- i.e. at least 4.25MB (ROM-01) or 5MB (ROM 3) of total system RAM,
RamFAST SCSI + 120MB or larger SCSI hard disk OR 120MB or larger HD-on-a-card
IDE drive (e.g. Alltech's Focus Hard Card or SHH's Turbo IDE series) with
System 6.0.1 installed, 8MHz/32k TransWarp or 9MHz/32k ZipGS or better
accelerator board, Stereo Card, Imagewriter II printer, two 3.5" and two 5.25"
diskette drives.

A minimum GS system that will run many older wares and still deliver a decent
operating system is a ROM-01 GS with the Apple 1MB Memory Expansion board, two
3.5" drives, at least one 5.25" drive, and  Imagewriter II printer, which boots
System 5.0.4 or System 6.0.1 from 3.5" diskette. --Dan DeMaggio, Rubywand,
David Empson, Supertimer, Randy Shackelford, Hal Bouma

Related FAQs Resources: R028LCA2CARD.TXT (text file)


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