Apple I

Apple I

First-batch Apple I board (1976), Deutsches Museum
Specifications
Developer	Steve Wozniak
Manufacturer	Apple Computer Company
Type	Single-board personal computer
Released	1976
Intro price	US$666.66 (assembled board)
Units sold	200 boards produced; 175 originally assembled
CPU	MOS Technology 6502 at 1.023 MHz
Memory	4 KB supplied, 8 KB on board; "fully expandable to 65K" through the edge connector
Storage	Optional Apple Cassette Interface
Display	Composite video, 40 × 24 upper-case text
Sound	—
OS / Firmware	256-byte monitor PROM; Integer BASIC loaded from cassette
Successor	Apple II

The Apple I (Apple-1) is the first product of the Apple Computer Company: a single-board computer designed by Steve Wozniak and sold in 1976 as an assembled circuit board, without case, power supply or keyboard. It uses a MOS Technology 6502 processor, 4 KB of RAM on a board with room for 8 KB, and a built-in video terminal section that drives a composite monitor. About 200 boards were made.

History

Wozniak finished the design in March 1976, in his apartment. The processor was the MOS Technology 6502, which had been introduced in 1975 at $25, far below the Intel 8080 and Motorola 6800. The display section grew out of the "Computer Converser", a terminal Wozniak had designed with Alex Kamradt, and the board artwork was laid out by Howard Cantin.

To pay for the first boards, about $1,000, Wozniak sold his HP-65 calculator for $500 (the buyer paid only half) and Jobs sold his Volkswagen van, for "another few hundred dollars" in Wozniak's account and $750 in the registry's. Wozniak and Jobs first planned to sell bare boards as a kit. Paul Terrell of the Byte Shop in Mountain View instead ordered 50 fully assembled computers at a wholesale price of $500 each, to retail at $666.66. The registry attributes the price to Wozniak's liking for repeating digits.

All components, including the IC sockets, were soldered at a factory. The chips were inserted by hand at Jobs's parents' house, the first 50 boards indoors and the next 50 in the garage, with Wozniak calling about once a week to correct mistakes.

After the Apple II appeared, Apple encouraged Apple I owners to upgrade, first with a discount on an Apple II and then with trade-ins, which is one reason so few Apple I boards survive.

Specifications

Apple I system specifications, as published by Apple

Item	Apple's figure
Microprocessor	MOS Technology 6502
Clock frequency	1.023 MHz
Effective cycle frequency	0.960 MHz, including refresh waits (four of every 65 clock cycles go to DRAM refresh)
Video output	Composite positive video, 75 Ω, level adjustable between zero and +5 V p-p by the potentiometer beside Molex connector J2
Line rate	15,734 Hz
Frame rate	60.05 Hz
Format	40 characters per line, 24 lines, automatic scrolling
Display memory	Dynamic shift registers (1 K × 7); the display is not memory-mapped
Character matrix	5 × 7
RAM	16-pin 4 K dynamic, type 4096 (2104)
On-board RAM capacity	8 KB (4 KB supplied)
Expansion	44-pin edge connector; "fully expandable to 65K"
Power supplies	+5 V at 3 A, ±12 V at 0.5 A, −5 V at 0.5 A
Input power	8-10 V AC (RMS) at 3 A and 26-28 V AC (RMS) centre-tapped at 1 A, both at Molex J1
Recommended transformers	Stancor P-8380 or Triad F31-X; Stancor P-8667 or Triad F40-X

The board has sockets for 8 KB and was supplied with 4 KB. More memory goes on the expansion connector, and Apple's limit for the whole system is 65 K.

Power at the edge connector

Only +5 V is regulated at the edge connector. The +12 V, −12 V and −5 V pins carry raw DC of approximately ±14 V, and expansion cards must regulate it themselves; Apple notes that there is no short-circuit protection on the raw DC. The board draws no more than 1.5 A from the +5 V regulator, which is rated at 3 A, leaving 1.5 A for expansion if the transformer can supply it. For DMA, break the solder jumper marked DMA.

Address map

Apple documents three regions. The display is not one of them.

Apple I address map, from the Apple-1 Operation Manual

Address	Function
$0000 upward	RAM: 4 KB supplied, 8 KB maximum on board; further RAM on the expansion connector
$D010	PIA, keyboard data. High-order bit equals 1
$D011	PIA, keyboard control. High-order bit indicates "key ready"; reading the key clears the flag, the rising edge of the keyboard strobe sets it
$D012	PIA, display data. Lower seven bits are the character out; the high-order bit is a "display ready" input, 1 = ready, 0 = busy
$D013	PIA, display control
$FF00-$FFFF	256-byte monitor PROM

The display memory is a set of dynamic shift registers, 1 K × 7, clocked round continuously. A program writes a character by polling $D012 and storing to it, one character at a time; there is no screen buffer to read back.

Integer BASIC is loaded from cassette into RAM at $E000 (the registry's instructions are to load E000.EFFF and start it with E000R). It is not in ROM.

Video

Apple's figures for the video output:

• Composite positive video (sync and video combined) from a 75 Ω source.
• The level is adjustable between zero and +5 V p-p with the potentiometer beside Molex connector J2. A picture that is too bright or too dim on a given monitor may need only this control.
• 40 characters per line, 24 lines, automatic scrolling; 5 × 7 upper-case characters.

The two outside pins of the video Molex connector supply +5 V and +12 V for Apple accessories, so take care when probing it. Apple names Motorola and Ball as makers of monitors that connect directly.

Production batches

200 Apple I boards were produced, in two batches; according to Wozniak, 175 were originally assembled. The first 50 went to the Byte Shop.

Apple I production batches

Batch	Built	Identifying features
First batch	Around April 1976	"Apple Computer 1" legend; round ceramic decoupling capacitors. Some boards sold through the Byte Shop have a handwritten serial number on the back, which the registry attributes to Steve Jobs
Second batch	Second half of 1976, by a different board manufacturer	Rhombic logo with the letters NTI under the "Apple Computer 1" legend; square multilayer decoupling capacitors, usually green; board colour differs

Individual boards also differ in details such as electrolytic capacitor colour; the Apple-1 Registry documents each surviving board with photographs.

Operation

Pressing RESET enters the 256-byte monitor PROM, which displays a backslash and a carriage return. Commands are typed a line at a time, up to 128 characters, and nothing executes until RETURN is pressed.

Monitor commands, from the Apple-1 Operation Manual

Command	Function	Example
:	Store bytes from the most recently opened location	300: A9 00
.	Range delimiter between two addresses, for dumping a block	4F.52 56 58.5A dumps three blocks
R	Run a program at the most recently opened address	E000R
ESC	Cancel the line; echoes backslash-return
SHIFT-O (back arrow)	Backspace; echoes an underline
Blank or comma	Delimiter only; a string of them acts as one

The monitor has no register display, no breakpoints and no "continue" command. A running program is stopped with RESET, which returns to the monitor.

Checking the board

The monitor's prompt doubles as a memory test. Apple: "A backslash alone (cursor remains on same line as backslash) indicates bad page 0 RAM." The monitor cannot work without page-zero RAM, so a prompt that does not drop to a new line points there first.

Apple's four-step test exercises the keyboard, display and supplies together: press RESET; type :A9 AA 20 EF FF E8 8A 4C 2 0 and RETURN; type .A and RETURN to list it back; type R and RETURN. The display should fill with a continuous stream of ASCII characters until RESET is pressed.

Software

Apple's own manual lists no application software. The Apple-1 Registry lists the software Apple made available on cassette in 1976: BASIC, Blackjack, a disassembler, an extended monitor, Hamurabi, Mastermind, Lunar Lander and Star Trek.

Surviving boards

The Apple-1 Registry's count is 74 verified boards and 20 almost-verified, 94 in all, with a further nine that may exist or may be double-listed and three believed no longer to exist. Nineteen are in museums. The count changes as boards are authenticated. The registry also records sale prices board by board, keyed to its registry numbers; published auction figures often mix hammer prices, premiums and private sales.

Museums with an Apple I on display include:

• Computer History Museum, Mountain View (registry #5, first batch)
• Smithsonian, Washington DC (#62, first batch)
• Science Museum, London (#39, second batch)
• Powerhouse Museum, Sydney (#26, first batch)
• Deutsches Museum, Munich (#31 "Copson", first batch, pictured above)
• Heinz Nixdorf MuseumsForum, Paderborn (#38, second batch)

Documentation

• Apple-1 Operation Manual 1976: Apple's 15-page manual, hosted here, with the specifications, the monitor listing, expansion notes and schematic drawing 00101 sheets 1-3.
• The Apple-1 Registry holds scans of the Apple-1 Cassette Interface manual and the preliminary BASIC manual.

Related pages

• Apple II
• Apple-1 Operation Manual 1976