Editing Exidy Sorcerer (section)

== Description ==

The Sorcerer design combined elements of the popular MITS-derived [[S-100 bus]] architecture, not yet standardised, with custom display and i/o circuitry, all housed within a custom "closed" case. The ROM-pac idea came from Howell Ivy's days at Ramtek, where he started working on arcade games before joining Exidy. The machine included the [[Zilog Z80]] and various bus features needed to run the [[CP/M]] [[operating system]]; a port of CP/M was done by the four-man software team at Exidy led by Vic Tolomei, in consultation with Digital Research. The "closed" case featured a built-in keyboard similar to later machines like the [[Commodore 64]], and the [[Atari 8-bit computers]]. The Sorcerer's keyboard was a high quality unit with full "throw". The keyboard included a custom "Graphics" key, which allowed easy entry of the extended character set, without having to overwork the Control key, the more common solution on other machines. Leading its peers, the Sorcerer included lower-case characters in ROM, as well as user-programmable characters stored in RAM.

Unlike most S-100 CP/M machines of its era, the Sorcerer did not have any internal expansion slots, and everything that was needed for basic computing was built-in. A standard video monitor was required for display, and optionally a standard audio cassette deck was needed for data storage. The Sorcerer included a small [[read-only memory|ROM]] containing a simple [[Machine code monitor|monitor program]], written by John Borders, which allowed the machine to be controlled at the [[machine language]] level, as well as load programs from [[cassette tape]] or [[ROM cartridge|cartridges]]. The cartridges, known as "ROM PAC"s in Exidy-speak, were built by replacing the internal tape in an [[8-track cartridge|eight-track tape]] cartridge with a circuit board and [[edge connector]] to interface with the Sorcerer. These allowed the Sorcerer to run applications immediately on start-up, rather than having to load them from tape cassette like its peers.

The machine was usable without any expansion, but if the user wished to use S-100 cards they could do so with an external expansion chassis. This was plugged in via a 50-way ribbon cable to the expansion slot in the rear of the Sorcerer. The Exidy S-100 chassis is a large external cage which included a full set of S-100 slots, allowing the Sorcerer to be used as a "full" S-100 machine. 

Using the same S-100 expansion slot, a user could directly attach [[floppy disk]]s and boot from them into CP/M (without which the disks were not operable). A later form factor of the Sorcerer combined the floppies, and a small monitor into a single box, that resembled the TRS-80 model II.  A Winchester drive was also later offered. 

=== Graphics === 
Graphics on the Sorcerer were impressive, with a resolution of {{resx|512×240}}, when most machines of the era supported a maximum of {{resx|320×200}}. These lower resolutions were a side effect of the inability of the video hardware to read the screen data from RAM fast enough; given the slow speed of the machines they would end up spending all of their time driving the display. The key to building a usable system was to reduce the total amount of data, either by reducing the resolution, or by reducing the number of colors.

The Sorcerer instead chose another method entirely, which was to use definable character graphics. There were 256 characters to choose from for each screen location. The Sorcerer character set was divided into two halves: the lower half was fixed in ROM and contained the usual [[ASCII]] character set; while the upper half was defined in a dedicated region of RAM. This character RAM would be loaded with a default set of graphics from ROM at reset, but could be re-programmed and used in lieu of [[pixel]]-addressable graphics. In fact, the machine was actually drawing a {{resx|64x30}} display ({{resx|8x8}} pixel characters) which was well within the capabilities of the hardware. However, this meant that all graphics had to lie within a checkerboard pattern on the screen, and the system was generally less flexible than machines with "real" graphics. In addition, the high resolution was well beyond the capability of the average color TV, a problem they solved by not supporting color. In this respect the Sorcerer was similar to the PET and [[TRS-80]] in that it had only "graphics characters" to draw with. Given these limitations, the quality of the graphics on the Sorcerer was otherwise excellent. The programmable character RAM offered significant advantages, which included the ability to provide a form of animation by re-defining individual character bitmaps at runtime. Clever use of several characters for each graphic allowed programmers to create smooth motion on the screen, regardless of the character-cell boundaries. 

=== Sound === 
A more surprising limitation, given the machine's genesis, is the lack of sound output. Enterprising developers standardized on use of two pins of the [[parallel port]], to which users were expected to attach a speaker.

=== Software ===
A ''Standard BASIC'' cartridge was included with the machine. This cartridge was essentially the common [[Microsoft BASIC]] already widely used in the CP/M world. One modification was the addition of single-stroke replacements for common BASIC commands, pressing {{keypress|GRAPHICS-P}} would insert the word <code>PRINT</code> for instance, allowing for higher-speed entry. The machine included sound in/out ports on the back that could be attached to a [[cassette tape]] recorder, so BASIC could load and save programs to tape without needing a disk drive. An ''Extended BASIC'' cartridge requiring 16&nbsp;KB was also advertised, but it is unclear if this was actually available; Extended BASIC from Microsoft was available on cassette. Another popular cartridge was the ''Word Processor PAC'' which contained a version of the early word processor program [[Spellbinder (software)|Spellbinder]]. 

=== Third Party Add-ons ===
Numerous third party hardware and software applications were developed for the Sorcerer and the S-100 bus. Examples include:
* The Montfort Brothers made an [[EPROM]] PAC with a rechargeable battery inside and 16&nbsp;KB RAM with an external write-protect switch. Thus bootable software could be uploaded to the pack and kept for a longer period.
* Montfort also made a general purpose IO (GPIO) ROM PAC, which includes 8K RAM and an I/O port with individually- or group-addressable I/O lines.

Numerious active user groups, particularly in Australia (SCUA), the Netherlands (ESGG), the U.K. (ESC) and the U.S. (SUG), published regular newsletters including The Sorcerer's Apprentice. Many of these can be found in the various internet archives, see links below.

=== RAM expansion ===
Many CP/M machines were designed to allow the full 16-bit [[address space]] of 64&nbsp;KB to be populated by memory. This was problematic on the Exidy Sorcerer. 32&nbsp;KB could easily be populated. Another 16&nbsp;KB was the ROM cartridge address space. This could be populated, but required disabling the ROM cartridge capability. The last 16&nbsp;KB was required by the system for [[input/output|I/O]], particularly for the video, and would have required extensive system modification.