MESS emulates three different ROM revisions of the Apple ||GS
For each driver, MESS supports up to four devices
These systems requires full keyboard emulation to work correctly. At startup, full keyboard emulation mode is enabled by default. Whilst in full keyboard emulation mode, some key associated functionality may be disabled (like the ESC key for EXIT). The keyboard emulation mode is toggled using the “Scroll Lock” key (by default).
The Apple ||GS was originally the “IIX” project, which was intended to use the 65816 along with a special slot that could be used to add either an 8088 (for PC compatibility) or a 68000 (to run Mac software). But the 65816 was running late (William D. Mensch famously laid it out by hand on his kitchen table, using no computer assistance) and Apple management killed the project. It was later resurrected under the codename “Phoenix” (and later “Gumby” and “Rambo”) when the 65816 was ready, and it did make it to market despite a lukewarm response from Apple management. The ||GS was made possible by the development of the “Mega II” ASIC, which contained the entire circuitry of an enhanced Apple IIe except for the CPU, ROMs, and RAM on a small single chip, but it was Steve Wozniak himself who gave a crucial boost to the engineers, coming up with a scheme that would maintain very high Apple II compatibility while still letting the ||GS be its own machine. The “Mega II” ASIC was later used as the basis of the Apple IIe card for the Macintosh LC series computers. In tribute, the first production run of the ||GS had Woz's signature stamped onto the case.
Sales were strong initially and the ||GS even outsold the black and white Macintosh units that were its contemporary. The ||GS was the first Apple released that could show the Mac GUI in color and the first released machine with the new ADB peripheral connection (the Mac II and SE were introduced several months later). Apple management was terrified of hurting Mac sales so they had forced the engineers to run the 65816 much slower than the 7 MHz 68000 of the Mac Plus (Wozniak and the engineering team had wanted to run the 65816 at 8 MHz). Even so, the ||GS's all-assembly language Toolbox was eventually tuned to the point where even at 2.8 MHz the GUI felt as snappy as its more powerful cousin. The slow CPU did hurt it for games though - games on the ||GS typically looked good and sounded great but animated poorly. The Apple ||GS disappeared from the market in 1992.
In one final gasp, the Apple II supporters at Apple designed the Apple ||GS Plus, code named “Mark Twain”. It was rumored to have an 8 MHz 65C816, a built in SuperDrive, 2MB on the motherboard, and a hard drive. Apple management originally green lighted the new machine and reserved time during a satellite broadcast in September of 1991 to introduce it to the world, but it was killed at the last minute due to the usual objections that it could hurt the Macintosh. A prototype leaked out of Apple years later and was much less ambitious than was originally thought: it contained the same ROM 3, but with 2 MB of RAM, an on-board SCSI controller, and an internal SCSI HDD. So even if it had been introduced it would have been too little too late.
The Ensoniq chip in the Apple ||GS was a brilliant move by Apple, but like a lot of things related to the ||GS it was something of an accident. Although the 5503 powered several successful Ensoniq synthesizers (the ESQ-1, SQ-80, and the Mirage sampler), Bob Yannes remembered the impact of his SID on the Commodore 64 and wanted to get the chip into a computer. He first called Commodore, but they weren't interested in chips they didn't make (they also passed on the 65816 CPU - imagine a C64 sequel with the 65816 and 5503!) He called Apple and got bounced around to various people until it hit an engineer on the ||GS team who was heavily into electronic music. As usual getting management to accept the chip was an uphill fight - originally the sockets for the 5503 and its RAM were to be placed on the board and the chips sold separately, but finally they realized the cost difference was minor at that point and included the chips in every machine sold. It was so close that the system software shipped with an error code defined for “Ensoniq not present”.
The chip also caused legal trouble with Apple Records, which resulted in Apple never again putting a hardware synthesizer chip into a computer. The Macs relied on a 4-voice DMA setup similar to the Commodore Amiga for years and now just uses software synthesis.
The “SmartPort” external drive port supports both Apple IIe/IIc UniDisks (3.5” and 5.25” models) and the newer Apple 3.5 Drive which was shared with the Macintosh. You could have a total of 2 UniDisks and 4 Apple 3.5 Drives daisy-chained, although such a configuration would have put quite a strain on the stock power supply. Some companies also made SmartPort compatible harddisks, but these were relatively slow and most ||GS users used an add-on SCSI card and drive instead.
The difference between a UniDisk and a ||GS 3.5” drive is that the IIGS drive is controlled directly by the computer while the UniDisk has a separate 6502 processor (similar to the Commodore 15×1 drives). The UniDisk is thus much slower (up to 4x slower) than a ||GS 3.5” drive.
Apple and third parties both sold SCSI cards for the ||GS, and Applied Engineering sold a “high density” floppy drive that got double the density by spinning the disk at half speed. A card was released that permitted Apple IIe and ||GS systems to use the 1.44MB SuperDrive from the later Macs but it's extremely rare.
The ||GS was available initially as an upgrade motherboard for the Apple IIe - you got a board which would fit in the IIe case and had connectors for the IIe's power supply and internal keyboard and replacement stickers which changed the old “Apple” and “IIe” in Apple's original font into “Apple IIgs” in the newer Apple font. All the other connectors were still present, and you could buy an ADB keyboard and mouse to use with it as well. A IIe upgrade version of the ROM 3 motherboard was never made however.
The initial ROM 0 ||GS shipped with defects in the “Video Graphics Controller” custom ASIC that caused fringing in the old Apple II video modes under some circumstances. A new VGC and a new ROM chip were a free upgrade to bring those systems up to ROM 1 specs. (The ROM 0 firmware also had significant bugs - some software and add-on hardware won't work with it).
The Apple ||GS had a lot of graphic modes. All modes used a 12-bit palette for 4096 colors.
The ||GS also had all the graphics modes found on the //c.
(info from old-computers.com and other sources)
”][”, “II”, and ”//” tend to be used pretty much interchangeably for any model of Apple II computer, although, practically speaking, there are a few usages which may provoke a correction.
”][” is the original Apple II symbol. It appears on all early II's and II+'s as well as on the Disk ][ drive. It is, easily, the most attractive and distinctive II symbol; but, it is also associated with old Apple II's. The ”//” usage is generally associated with the “c” and newer “e” models.
The generally preferred machine designations are:
The ||GS with ROM version 3 has an audio recording built-in. Upon booting, when you see the “Open Apple” move back and forth on the screen, press <Control> <Open Apple> <Option> <N>. You will hear the ||GS design team shouting “Apple II!”, and see the designers' credits.
ROM 1 has the same Easter Egg without the audio clip due to its smaller ROM.