Apple II
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| Apple II with two Disk II drives (Musée Bolo, Lausanne) | |
| Specifications | |
|---|---|
| Developer | Steve Wozniak |
| Manufacturer | Apple Computer |
| Type | Personal computer |
| Released | April 1977 (West Coast Computer Faire) |
| Discontinued | May 1979 (replaced by the Apple II Plus) |
| Intro price | US$1,298 (4 KB); US$2,638 (48 KB) |
| CPU | MOS Technology 6502 at 1.023 MHz |
| Memory | 4 KB to 48 KB on the main board; 64 KB with the Language Card |
| Storage | Cassette interface; Disk II from July 1978 |
| Display | Composite video: 40 × 24 text; 40 × 48 low-resolution graphics in 16 colours; 280 × 192 high-resolution graphics in 6 colours |
| Sound | 8 Ω speaker driven by a soft switch |
| ROM | 12 KB: Integer BASIC and the Apple System Monitor |
| OS / Firmware | Integer BASIC in ROM; Apple DOS 3.1 and later on disk |
| Predecessor | Apple I |
| Successor | Apple II Plus |
The Apple II is Apple Computer's second computer, designed by Steve Wozniak and introduced at the first West Coast Computer Faire in April 1977.[1] Unlike the Apple I it came complete, in a plastic case with a keyboard and a switching power supply, with Integer BASIC in ROM, colour graphics on a composite monitor or television, and eight expansion slots.[2] Board-only machines shipped from 10 May 1977 and complete systems from 10 June 1977. It sold for $1,298 with 4 KB of RAM or $2,638 with 48 KB, without monitor or cassette recorder.[1] The Apple II Plus replaced it in 1979.[1]
Board revisions
[edit | edit source]Apple's reference manual describes two versions of the original main board.[2] A Revision 0 board lacks the single metal video connector pin between the four-pin video connector and the video adjustment potentiometer in the upper right corner; a Revision 1 board has it. Revision 1 added:
- a colour killer, which turns off the colour burst in text mode so that text is not tinted or fringed;
- a power-on reset circuit. On a Revision 0 board you press RESET after switching on, and the keyboard delivers a random character that has to be cleared;
- red and blue in high-resolution graphics. A Revision 0 board shows only black, white, violet and green.
Apple II History adds that Revision 1 also brought jumpers for PAL and SECAM television standards and separated the speaker from the cassette output.[1] Early production machines had cases painted after moulding, a toggle power switch in place of the later rocker switch, and no ventilation slots in the sides.[1]
The later RFI (reduced-emission) main board, 820-0044, is documented in Apple's Addendum to the Apple II Reference Manual, hosted at Apple II Schematics. Apple's service parts list gives the RFI Apple II/II Plus main board with RAM as 661-91205.[3]
Architecture
[edit | edit source]| Sub-system | Detail |
|---|---|
| CPU | MOS Technology 6502 at 1.023 MHz, derived from the 14.318 MHz master oscillator |
| Address and data bus | 16-bit address, 8-bit data: 64 KB address space |
| ROM | Six 24-pin sockets, each a type 9316B 2,048 × 8 device: 12 KB of ROM address space from $D000. The ROMs resemble 2316 and 2716 parts but their chip selects differ, so they cannot be plugged in directly |
| RAM | Three rows of eight sockets (C, D and E); each row all 4096-type (4K) or all 4116-type (16K). Nine totals from 4 K to 48 K, set by the memory configuration blocks at D1, E1 and F1 |
| Expansion RAM | Apple Language Card, A2B0006: 16 K in place of the ROM, giving 64 K |
| Video | Text 40 × 24 (5 × 7, upper case; normal, inverse and flashing); low-resolution 40 × 48 in 16 colours; high-resolution 280 × 192 in 6 colours (4 on a Revision 0 board) |
| Sound | A small 8 Ω speaker under the keyboard on the left, toggled by referencing the speaker soft switch at $C030 |
| Fixed I/O | Game I/O (paddles and buttons, annunciator outputs), cassette in and out, composite video, RF modulator header |
| Expansion | Eight 50-pin slots, 0 to 7 |
Memory map
[edit | edit source]| Range (hex) | Size | Use |
|---|---|---|
| $0000-$BFFF | 48 KB | RAM (three 16 KB rows) |
| $C000-$C07F | 128 B | Built-in I/O and soft switches (keyboard, speaker, paddles, display modes) |
| $C080-$C0FF | 128 B | Peripheral slot I/O, 16 bytes per slot |
| $C100-$C7FF | 1.75 KB | Slot ROMs, 256 bytes each for slots 1 to 7 (slot 0 has none) |
| $C800-$CFFF | 2 KB | Expansion ROM space shared by all slots; I/O STROBE (pin 20) goes low for any address in this range |
| $D000-$FFFF | 12 KB | ROM, six 2 KB sockets; a Language Card substitutes RAM here |
The annunciator outputs on the Game I/O connector are four one-bit outputs, each a pair of soft switches: $C058/$C059 (AN0), $C05A/$C05B (AN1), $C05C/$C05D (AN2) and $C05E/$C05F (AN3). The first address of each pair turns the output off and the second on; off is near 0 V and on near 5 V, and the setting cannot be read back.[2]
Expansion slots
[edit | edit source]Apple's peripheral connector pinout (Figure 21 and Table 33 of the reference manual):[2]
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | I/O SELECT (low when the CPU references page $Cn) | 26 | GND |
| 2-17 | A0-A15, buffered address bus | 27 | DMA IN |
| 18 | R/W, buffered | 28 | INT IN |
| 19 | SYNC, slot 7 only | 29 | NMI |
| 20 | I/O STROBE ($C800-$CFFF) | 30 | IRQ |
| 21 | RDY | 31 | RESET |
| 22 | DMA (held high by 3 kΩ to +5 V) | 32 | INH: disables all on-board ROMs (held high by 3 kΩ) |
| 23 | INT OUT | 33 | −12 V, 200 mA for all cards together |
| 24 | DMA OUT | 34 | −5 V, 200 mA for all cards together |
| 25 | +5 V, 500 mA for all cards together | 35 | COLOR REF, 3.5 MHz, slot 7 only |
| 36 | 7M, 7 MHz clock | ||
| 37 | Q3, 2 MHz asymmetrical clock | ||
| 38 | Φ1 | ||
| 39 | USER 1: pulling it low disables all internal I/O address decoding | ||
| 40 | Φ0 | ||
| 41 | DEVICE SELECT ($C0n8-$C0nF) | ||
| 42-49 | D0-D7, buffered bidirectional data bus | ||
| 50 | +12 V, 250 mA for all cards together |
Pin 50 is +12 V and pin 26 is ground. The fastest clock on the slots is 7M; 14M, and COLOR REF except on slot 7, stay on the main board. The current limits are for all cards together. Address lines can drive 5 LSTTL loads per card, data lines one, I/O SELECT and DEVICE SELECT ten, and I/O STROBE four. Data is valid 300 ns into Φ0 on a write and must be stable at least 100 ns before the end of Φ0 on a read.[2]
Software
[edit | edit source]The original Apple II has Integer BASIC and the Apple System Monitor in ROM. Its monitor ROM goes straight into the monitor on RESET and supports the STEP and TRACE commands. The Autostart ROM fitted to every Apple II Plus adds the ESC cursor-movement keys, CTRL-S stop-list and a warm or cold start on RESET, but drops STEP and TRACE.[2]
The Disk II and Apple DOS 3.1 became available in July 1978, at an introductory $495 including the controller card ($595 once in stock). DOS 3.1 formatted 13 sectors per track, 113 KB per disk.[4]
Power supply
[edit | edit source]The supply is a switching design built by Astec. Apple's figures:[2]
| Output | Nominal | Full-load current |
|---|---|---|
| +5 V | +5.0 V | 2.5 A |
| +12 V | +11.8 V | 1.5 A (about 2.5 A intermittent) |
| −5 V | −5.2 V | 250 mA |
| −12 V | −12.0 V | 250 mA |
Input is 107-132 V AC or 214-264 V AC, selected by a switch; consumption is 60 W at full load and 79 W intermittent. The positive 12 V rail is specified at +11.8 V, so a reading slightly under 12 V is normal. If an output is short-circuited, the supply stops its oscillator, pauses for about a second and tries again, repeating until the short is removed: a ticking supply usually has a load fault downstream.[2] The main board has no regulators of its own; all four rails come regulated from the supply.[2]
Apple's component listings for the two Astec supplies (AA11040 and AA11040B) are hosted as File:Apple Astec Power Supplies Service Package 1982.pdf.[5] The Apple II General Maintenance page gives both lists; check which supply you have before ordering parts. Apple's later replacement supply (661-0455) is 1.5 inches longer than the original and fits any Apple II or II Plus, although it may foul the speaker, which Apple's procedure moves back about an inch.[3]
The primary side of the supply is not isolated from the mains. Apple's manual warns that "much of the internal circuitry is not isolated from the power line". Discharge the primary capacitors and confirm with a meter before working on it, and see Capacitor Failure Symptoms.[2]
Troubleshooting
[edit | edit source]Apple's service troubleshooting chart lists probable causes in order. The first entries:[3]
| Symptom | Probable causes, in order |
|---|---|
| Will not boot; drive comes on | RAM row E; RAM on the Language Card at E2; motherboard |
| No beep, no message; random characters on screen at power-on; drive does not come on | RAM row C; "F8" ROM at F3 on the motherboard; "F8" ROM on the Language Card at E2; motherboard |
| Programs run erratically, often crash | RAM; motherboard |
| System dead (no beep, no video), with or without the power light | Power supply; motherboard |
| No video display | Video cable; video pot adjustment; motherboard |
The full chart, and Apple's chip swapping chart by board location, are on Apple II General Maintenance. Two further checks from the reference manual:[2]
- The INH line runs to every slot, and a card that pulls it low disables every ROM on the main board. A machine that is dead with cards fitted and alive with them out may have one card holding INH low.
- The memory configuration blocks must match the chips. Never put 4K chips in a row strapped for 16K or the reverse, do not leave a row unstrapped, and do not strap two rows into the same range. All three blocks should be strapped the same way.
Text faults can be the character generator, a 2513 at A5, or the 74166 shift register at A3.[2]
Documentation
[edit | edit source]- Apple II Reference Manual (1979): hardware reference, hosted.
- Apple II Schematics: Apple's Addendum with the RFI main board schematic.
- Apple II and II Plus Technical Procedures: Apple's service procedures for the Apple II and II Plus (take-apart, diagnostics, troubleshooting and chip swapping charts, parts list).
- File:Apple Astec Power Supplies Service Package 1982.pdf: Astec supply schematics and component lists.
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 Steven Weyhrich, "The Apple II, cont.", Apple II History, chapter 4, https://apple2history.org/history/ah04/ . Sections "Product Introduction" (West Coast Computer Faire, April 1977; board-only machines shipped 10 May 1977 and complete systems 10 June 1977), "Cost" ($1,298 with 4K, $2,638 with 48K), "Experiences of Early Users" (early cases painted, toggle power switch, no side vents), "Enhancements" (Revision 0 and Revision 1 boards), "Apple-1 Upgrades", and the timeline (Apple II, April 1977 to May 1979).
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 Apple Computer, Apple II Reference Manual, 1979, hosted as File:Apple II Reference Manual 1979.pdf (described at Apple II Reference Manual). Specifications (text 40 × 24, 5 × 7 characters; low-resolution 40 × 48 in 16 colours; high-resolution 280 × 192 in 6 colours); the speaker ("a small 8 ohm speaker" on the left under the keyboard, soft switch at 49200, $C030); "Revision 0 / Revision 1 Board" and the Autostart and old Monitor ROMs, pp. 25-26; power supply specification, p. 92 (supply voltages +5.0, +11.8, −12.0 and −5.2 V; full-load currents; 60 W full load and 79 W intermittent; short-circuit shutdown and restart); main board description (RAM rows C, D and E; six ROM sockets; configuration blocks at D1, E1 and F1); video generation (2513 character generator at A5, 74166 at A3); RAM and ROM sections; annunciator outputs (Table 9); peripheral connector pinout (Figure 21) and signal description (Table 33).
- ↑ 3.0 3.1 3.2 Apple Computer, Apple II/II Plus Technical Procedures, from Apple Service Technical Procedures: Apple II/Apple III Archived Products, Volume One (072-0231), hosted as File:Apple II and II Plus Technical Procedures.pdf. Section 1, Take-Apart, pp. 1.2-1.11 (written for the pre-RFI Apple II; housing, motherboard, keyboard, power supply, speaker modification, power cable extension); Section 3, Troubleshooting: Apple II Troubleshooting Chart pp. 3.3-3.4 and Apple II Chip Swapping Chart pp. 3.5-3.8 (rev. Sep 82); Illustrated Parts List, pp. IPL.3-IPL.7 (rev. Jan 89): 661-91205 Apple II/II Plus motherboard RFI with RAM, 661-0455 Apple II power supply, the longer replacement power supply, ROM part numbers, Disk II controller PROMs P5A 341-0027 and P6A 341-0028.
- ↑ Steven Weyhrich, "The Disk II", Apple II History, chapter 5, https://apple2history.org/history/ah05/ . Source for: availability in July 1978 with DOS 3.1; introductory price $495 including the controller, $595 otherwise; thirteen sectors per track and a formatted capacity of 113K.
- ↑ Apple Computer, Apple Products Information Package: Astec Power Supplies, 6 August 1982, hosted as File:Apple Astec Power Supplies Service Package 1982.pdf. Component listings for the AA11040 (pp. 12-13) and AA11040B (pp. 14-15), with schematics and layouts.