• CPU: MOS Technology 6502 1 MHz
• Memory: 4 kB DRAM, expandable to 8 kB on board, or up to 52 kB with third-party expansion hardware
• Screen: 40×24 characters
• Storage: Optional cassette interface
• Keyboard: No keyboard (sold separately)

MESS supports the emulation of apple1 with a “cassette” (cass) device, for tapes in .wav format (see below).

Also a “snapshot” (dump) feature is present for .snp files.

Upon boot or reset, the system displays a “\” and a blinking ”@” cursor on the next line. The blinking ”@” is the Apple 1's video cursor. The “\” is the prompt for the Monitor program. From the Monitor, you can examine or change memory or execute another program.

You can always interrupt a program and return to the Monitor by pressing the Apple 1's RESET switch (“F12”). This will not clear the screen or disturb memory contents.

To cold-boot the system, clearing the screen and memory, press the MESS Reset key (“F3”, in partial emulation mode only).

The Apple 1's CLEAR SCREEN switch (“F2”) will clear the screen and place the cursor at the upper left corner. This only clears the video hardware, not the computer's memory, so you can use it whenever you like.

To start the cassette interface's mini-monitor from the Monitor, type the Monitor command

C100R

This mini-monitor will let you write memory regions to a cassette image or read a cassette image into memory. It will only execute a single line of commands, and will then return you to the main Monitor, but this line can contain several write or read commands.

• Cassette write command, writing data from memory at $xxxx-$yyyy

xxxx.yyyyW

• Cassette read command, reading data into memory at $xxxx-$yyyy

xxxx.yyyyR

The starting and ending addresses xxxx and yyyy should be 4-digit hexadecimal addresses. The starting address can actually be shorter than 4 digits, but to be safe, the ending address should be exactly 4 digits. (A bug in the cassette mini-monitor will cause digits missing from the ending address to be replaced by the trailing digits of the starting address, and if the starting address does not end with zeroes, much more data will be written or read than expected.)

If a command line contains multiple write or read commands, the corresponding memory regions will be written or read in sequence. These commands may be separated by spaces, which are ignored.

When a region is written, its data is preceded by a 10-second leader. When a region is read, the leader can vary in length but should be at least 4-5 seconds.

If the cassette image doesn't contain enough data to fill a region, the mini-monitor will hang waiting for the remaining data, and the system must be reset.

When all the cassette commands have been executed, the mini-monitor will return to the Monitor, which will display a “\” prompt.

Some cassette command examples:

• To read Apple 1 BASIC from cassette

E000.EFFFR

• To write a BASIC program to cassette, with BASIC's default LOMEM= setting of 2048

4A.00FFW800.FFFW

• To read a BASIC program from cassette, with LOMEM=768

4A.00FFR300.FFFR

Once Apple 1 BASIC is loaded into memory, it can be started with the Monitor command

E000R

This will start BASIC from scratch, removing any existing BASIC program and data. To return to BASIC from the monitor while preserving the current program and data, use the command

E2B3R

The BASIC prompt is a ”>”. Apple 1 BASIC is generally similar to Apple II Integer BASIC, but without the latter's graphics commands.

This system 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).

Different RAM configurations are possible for the apple1 in MESS. You can switch between them, changing the -ramsize parameter. At command line, you simply have to add -ramsize ram_value, where ram_value can assume one of the following values

4k
8k
12k
16k
20k
24k
28k
32k
36k
40k
44k
48k (default)

• The cassette interface and $E000-$EFFF DRAM are always included; they cannot be switched off.
• The DRAM at $E000-$EFFF is not included in the RAM configured by MESS's -ram option, due to limitations in how MESS presently manages configurable RAM.
• Optional cassette interface is included and emulated.
• 4 KB of DRAM is mapped to $E000-$EFFF. This is required for Apple 1 BASIC.

The Apple 1 was a kit computer that was introduced and sold in small quantities in 1976.

Steve Wozniak (“Woz”), who worked for Hewlett-Packard at the time, wanted to build his own computer. He could afford neither the Intel 8080 (the most popular microprocessor at the time) nor the Motorola 6800 (his own preference). Therefore, he decided to build his computer around MOS Technology's new 6502 chip, which was quite compatible with the Motorola 6800 but far less expensive. He proceeded to write a BASIC interpreter for the chip, and then turned to designing the computer that would run it, using an earlier paper design for the Motorola 6800.

The resulting computer was easier to use and more affordable than many other kit computers of the time, sporting a keyboard interface and TV-compatible video terminal circuitry, all on a single circuit board. To keep costs down, the video memory was implemented using shift registers rather than RAM, with the downside being a slow display rate (60 characters per second). However, this was still much faster than the 10-character-per-second electromechanical Teletypes used with many early home computers. Wozniak's computer also used new, more compact 4-kilobit dynamic RAM chips instead of the 1-kilobit static RAMs used by most other designs. Wozniak promoted his computer and enhancements for it at the Homebrew Computer Club in Palo Alto, California.

Steve Jobs, who had worked with Woz on the game “Breakout” for Atari, convinced Woz to try to market and sell the computer. Together they formed the Apple Computer Company. Paul Terrell, the owner of The Byte Shop, a new local computer store, was interested in this computer, but only if it was fully assembled and came with a cassette interface, so Wozniak designed one.

Normally, the Apple 1 was sold “naked”, simply as a circuit board, without a monitor, power supply, keyboard, tape drive, etc. These would be added by the owner. Wozniak and Jobs assembled about 200 systems and sold about 170 of them. Most of these were later traded in to Apple for Apple IIs and were destroyed. About 30 to 50 are still in existence.

This machine was so popular that Jack Tramiel of Commodore (!) offered to buy Apple. Apple was, at the time, a major purchaser of MOS 6502 processors and Commodore owned MOS Technologies. Wozniak wanted $15,000 more than Tramiel offered. Needless to say, the deal fell through.

(info from old-computers.com)

• Apple 1 Owners Club
• Apple History
• Apple ][ History
• Apple 1 Manual
• Apple 1 at old-computers.com