Apple III
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| Apple III with Monitor III (Apple Museum, Prague) | |
| Specifications | |
|---|---|
| Manufacturer | Apple Computer, Inc. |
| Type | Business computer |
| Released | September 1980 |
| Discontinued | November 1983, superseded by the Apple III Plus; the line ended in April 1984 |
| Intro price | US$2,695 for the 256 KB system (A3S0256), February 1984 |
| CPU | Based on the 6502B with extended addressing; 2 MHz peak, 1.4 MHz average |
| Memory | 128 KB RAM; SOS supports a maximum of 512 KB. ROM is 4 KB, for initialisation and diagnostics only |
| Storage | Built-in 5.25-inch drive, 143,360 bytes per diskette; up to three more on a daisy chain; ProFile hard disk via a controller card |
| Display | 40×24 and 80×24 text, 40×24 in 16 colours; graphics 280×192 mono, 280×192 in 16 colours, 140×192 full 16 colour, 560×192 mono |
| Sound | 6-bit DAC with 64 volume levels, a one-bit square-wave generator and a fixed-frequency beep, 31 to 5090 Hz |
| Dimensions | 44.45 cm wide × 46.23 cm deep × 12.19 cm tall |
| Weight | 11.8 kg (26 lb) |
| OS / Firmware | Apple SOS; Apple III Business BASIC; Apple II emulation mode |
| Successor | Apple III Plus |
| Model no. | A3S0256 (256 KB system) |
The Apple III was Apple's first computer aimed at business users; a committee at Apple set its specification.[1] It was in production from September 1980 to November 1983, when the Apple III Plus replaced it.[1]
The infobox price is Apple's February 1984 dealer list price.[2]
Architecture and processor
[edit | edit source]Apple's own description of the processor is "based on the 6502B microprocessor, with extended addressing capability", running at 2 MHz peak, 1.4 MHz average.[3]
Apple II emulation was deliberately restricted in hardware: the emulation mode cannot use 80 columns, can see only 48 KB, and has none of the better graphics modes. Apple's engineers added chips specifically to prevent an emulated Apple II reaching the III's advanced features, in order to keep a clear marketing separation between the two machines.[1]
Memory
[edit | edit source]- 128 KB of dynamic RAM as standard, on a daughter board mounted above the main board[3][4]
- SOS supports a maximum of 512 KB[3]
- ROM is 4 KB and holds only initialisation and diagnostics.[3] There is no BASIC in ROM: SOS and the languages load from disk.
Display
[edit | edit source]Apple lists three text modes and four graphics modes:[3]
| Text | Graphics |
|---|---|
|
|
All text modes use a software-definable 128-character set that a program can change at any time.[3]
The RCA phono connector on the back carries black-and-white composite only. Colour, RGB and composite sync all come out of the DB-15, which also carries the four supply rails. On the black-and-white outputs, colour signals appear as a 16-level grey scale.[3]
Sound
[edit | edit source]The Apple III has a built-in 2-inch speaker, a miniature phone-tip jack on the back, and three separate audio generators:[3]
- a 64-level audio port driven by a 6-bit DAC
- a one-bit square-wave generator
- a fixed-frequency beep generator
The SOS audio driver produces tones from 31 to 5090 Hz over more than seven octaves, at 64 volume levels, with durations from 0 to 5 seconds in 1/60 second steps.[3]
Input/output and expansion
[edit | edit source]Apple's list:[3]
- One RS-232-C compatible serial port on a DB-25 female connector, with software-selectable baud rate and duplex mode
- A second DB-25 carrying the disk port, for up to three daisy-chained external drives
- Two DB-9 connectors for two joysticks, each with two push-buttons and a switch
- One DB-9, shared with the first joystick, for the Apple Silentype printer
- RCA phono video output and the DB-15 video connector
- Miniature phone-tip audio jack
- Four 50-pin expansion slots inside the cabinet
The two DB-25 sockets on the back therefore do different jobs: one is RS-232 and the other is the disk chain.
Apple II cards in Apple III slots
[edit | edit source]A bench comparison found the slots electrically identical to the Apple II's except for pins 19 (PH0), 35 (IOSYNC) and 39 (C02x), all unused on the Apple II.[4] Physical fit and firmware support are separate questions, so treat any particular card as unproven until tried.
Known faults
[edit | edit source]Apple II History records that "the first Apple III computers were plagued with nearly 100% defects and had to be recalled for fixes", and that Apple repaired the defective machines at no charge.[1]
A bench study of an early board (820-0043-00) by Steve Howell of AppleLogic examined the faults reported for the machine:[4]
- Chips working loose in sockets. The sockets are the same AMP and RN parts Apple used in the Apple II and IIe, and a cross-section showed nothing wrong with them. The author concludes that the cause was partial seating during automated DIP insertion at build, not thermal cycling, so seating the chips properly once is the repair. Apple's own troubleshooting procedure begins by checking that every IC on every board is seated.[5]
- PCB routing. The board is dense but has at most one track between the pins of a DIP, about eight thou wide with five thou clearance. The study did find untented vias close enough to adjacent pins that wave soldering could bridge them; when chasing an intermittent short, look at the vias next to socket pins.
- The real-time clock. The part is a National Semiconductor MM58167. The study finds the device reliable but sensitive to layout, and notes that its 32 kHz crystal is more than 40 mm away, routed between the R6551 UART at B1 and the R6522 VIA at B4. Apple's own fix for a clock that gains or loses is the calibration procedure below.
- The memory daughter board. The connectors are 2.54 mm Molex extended-pin types with three contact points per pin, and the example examined showed little corrosion.
- Heat. The Apple III has no fan and a cast aluminium base. Apple specifies an ambient temperature of 15 to 35 °C, the critical factor being "the deformation temperature of diskette cases".[3] The Apple III Plus owner's guide gives 0 to 45 °C, with the same critical factor.[6]
Service notes
[edit | edit source]Apple's service procedures for the Apple III and III Plus are hosted as File:Apple III and III Plus Technical Procedures.pdf.[5] Points from them:
- Memory boards come in 128K 12-volt and 256K 5-volt versions. A 12 V logic board has PROM 341-0041 at C13, PROM 341-0044 at C11 and resistor R58 at D14; a 5 V board has PROMs 342-0063 and 342-0061 and a jumper in place of R58. By 1986 Apple supplied only the 5 V 256K memory board and 5 V logic board, and replaced both boards when either failed in a 12 V system.[5]
- Before returning a logic board, remove the video interlace ROM (342-0145) at F5 if fitted; exchange boards come without it. New logic boards were shipped with black foam taped underneath to protect the encoder chip, which must be removed before fitting.[5]
- Power supply to logic board cables come in two types, matching either a two-row eight-pin or a one-row ten-pin connector on the logic board; check which before ordering. Apple's replacement supply has an 11-pin connector, and some Apple III logic boards need a 10-pin-to-11-pin cable.[5]
- Apple's troubleshooting starts from the SOS System Demonstration diskette with all peripherals disconnected, and at each step checks cables and IC seating before swapping modules.[5]
Clock calibration
[edit | edit source]The clock is calibrated with a trimmer capacitor near the centre of the keyboard area and Apple's Clock Calibration Program. With the 10-second interval selected (ALPHA LOCK down), the program's reading should be +560 ±9 after the speaker clicks twice; turn the trimmer clockwise to raise it and anticlockwise to lower it, allowing 10 seconds for each update. On the III Plus the trimmer is reached through a hole in the base plate under the keyboard. Apple's manual also gives a longer 24-48 hour method for fine correction.[5]
Power supply
[edit | edit source]Apple's published figures: a high-voltage switching supply producing +5, −5, +12 and −12 V, 100 watts maximum, from 107 to 132 volts at 60 Hz.[3]
The supply is an Astec AA11190, and Apple's service package gives its component listing.[7]
| Designator | Part |
|---|---|
| C1 | 0.22 µF 250 VAC metallised paper (class-X, across the mains) |
| C2 | 0.1 µF 250 VAC metallised paper |
| C3, C4 | 4700 pF 400 VAC ceramic (class-Y) |
| C5 | 0.1 µF 400 V polyester |
| C6, C7, C8, C9 | 100 µF 250 V electrolytic (primary reservoir) |
| C10, C18 | 220 µF 10 V |
| C11 | 0.001 µF 3 kV ceramic |
| C12, C21 | 0.22 µF 100 V polyester |
| C13, C14, C15, C16, C20, C22 | 1000 µF 10 V |
| C17, C23, C25 | 330 µF 16 V |
| C19 | 0.022 µF 100 V polyester |
| C24 | 680 µF 16 V |
| C26 | 0.1 µF 1 kV ceramic |
| F1 | Fuse, 2.75 A 125 V |
| VDR1 | Varistor, 260 VAC |
| R1 | Inrush thermistor, 4 Ω at 25 °C (or 6 Ω at 25 °C on some builds) |
| IC1 | TL431CP regulator |
The Apple III supply uses four 100 µF 250 V primary capacitors where the Apple II's AA11040B has four 47 µF 250 V parts (C5, C6, C24 and C25), and a 0.22 µF class-X capacitor where the Apple II uses 0.1 µF, so Apple II parts lists do not apply.[7]
Old class-X capacitors across the mains can crack and smoke. Mains potential is present on the primary side of this supply: see Apple II General Maintenance for the hazards and the procedure, and Capacitor Failure Symptoms for what a failing safety capacitor looks and smells like.
Things that are not faults
[edit | edit source]- No BASIC prompt without a disk: the Apple III has 4 KB of ROM and it holds diagnostics, not a language[3]
- Monochrome output on the RCA jack: that connector carries black-and-white composite only[3]
- Colour graphics appearing as grey levels on a monochrome monitor: Apple specifies a 16-level grey scale on the black-and-white outputs[3]
- A clock that drifts: calibrate it with Apple's procedure (above) before suspecting the MM58167[5]
Gallery
[edit | edit source]-
Apple III, front -
Apple III internal view
Related pages
[edit | edit source]- Apple III Plus
- Apple III Owner's Guide
- Apple III/III Plus Technical Procedures
- Apple II General Maintenance
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Steven Weyhrich, Apple II History, Chapter 7, "The Apple IIe", apple2history.org, sections on the Apple III project and the model timeline. The decision by committee to make the III a business machine; the deliberately limited Apple II emulation mode (no 80 columns, 48K only, none of the better graphics modes); the one-year target date; "the first Apple III computers were plagued with nearly 100% defects and had to be recalled for fixes" and Apple's repair of defective machines at no charge; the timeline Apple III September 1980 to November 1983 and Apple III Plus December 1983 to April 1984.
- ↑ Apple Dealer Price Lists for Apple III, Apple II, Macintosh and Lisa, Apple Computer, Inc., 15 February 1984 - hosted on this wiki as Apple Dealer Price Lists February 1984 (PDF). A3S0256 Apple /// 256K System (with system software) $2,695.00; A3S1256 Apple /// Plus 256K System $2,995.00; A3M0040 Apple /// 128K add-on memory kit $300.00; A2S2064 Apple //e 64K System $1,295.00.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 Apple III Owner's Guide, Apple Computer, Inc., 1981 - hosted on this wiki as File:Apple III Owners Guide 1981.pdf. Appendix E, System Specifications: size, weight and cast aluminium base; processor and clock speed; 128K of dynamic RAM; 4K of ROM for initialisation and diagnostics; power supply type, rails, 100 W maximum and 107-132 V 60 Hz input; ambient temperature 15 to 35 °C with the deformation temperature of diskette cases as the critical factor; the three text modes and four graphics modes; the RCA black-and-white composite output and the DB-15 carrying composite, colour, RGB, sync and the four rails; the three audio generators and their range; one RS-232-C DB-25 female serial connector, two DB-9 joystick connectors and one DB-9 shared with the first joystick for the Silentype; four 50-pin expansion slots; the 74-key keyboard; the built-in 5.25-inch drive at 143,360 bytes and up to three daisy-chained additional drives. SOS section: maximum 512 Kbytes of RAM, maximum disk size 32 Mbytes, 512-byte blocks.
- ↑ 4.0 4.1 4.2 Steve Howell, "What really killed the Apple III - a technology study of the Apple III", AppleLogic.org. This is a community technical study, not an Apple publication. It records the author's own bench examination of an early Apple III board (820-0043-00): the AMP and RN sockets are the same parts used in the Apple II and IIe and the author's conclusion that partial seating during automated DIP insertion, rather than thermal cycling, accounts for chips working loose; a cross-section of the socket; the finding that the board routing is high-density but not fine-line, with at most one track between DIP pins at about eight thou wide and five thou clearance, and the untented vias sited close enough to adjacent pins to risk bridging during wave soldering; the memory daughter board's 2.54 mm Molex extended-pin connectors, their three contact points per pin and the absence of significant corrosion on the example examined; the National Semiconductor MM58167 real-time clock and the placement of its 32 kHz crystal more than 40 mm away, routed between the R6551 UART at B1 and the R6522 VIA at B4; and the observation that the Apple III expansion slots are electrically identical to the Apple II's except for pins 19 (PH0), 35 (IOSYNC) and 39 (C02x), all unused on the Apple II.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Apple Computer, Apple III/III Plus Technical Procedures, from Apple Service Technical Procedures: Apple II/Apple III Archived Products, Volume One (072-0231), hosted as File:Apple III and III Plus Technical Procedures.pdf. Service notice on power supply connectors (10-pin and 11-pin); Section 0, Service Notes, p. 0.4 (rev. Jul 86): memory and logic board exchanges and automatic upgrades to 256K 5 V systems, the video interlace ROM 342-0145 at F5, the foam under the logic board, the two power supply cable types; Section 3, Troubleshooting, pp. 3.3-3.8 (diagnostic flowchart, swap steps, first checking cables and IC seating); Section 4, Modifications: clock kit (p. 4.2), setting the clock (p. 4.4), adjusting the clock speed (pp. 4.6-4.9, trimmer capacitor, Clock Calibration Program reading +560 ±9 on the 10-second interval), 256K RAM upgrade (p. 4.10: PROMs 341-0041 at C13 and 341-0044 at C11 with R58 at D14 for 128K 12 V boards; 342-0063 and 342-0061 with a jumper at D14 for 256K 5 V boards).
- ↑ Apple Computer, Apple III Plus Owner's Guide, hosted as File:Apple III Plus Owners Guide.pdf. System specifications: ambient temperature 0 to 45 °C (32 to 113 °F), critical factor the temperature at which disk cases can warp.
- ↑ 7.0 7.1 7.2 Apple Products Information Package - Astec Power Supplies, Apple Computer, Inc., originator Larry Sovulewski, 6 August 1982 - hosted on this wiki as File:Apple Astec Power Supplies Service Package 1982.pdf. Component listing for the Astec AA11190 (Apple III), pages 17 to 20, giving the capacitor values and voltages, the 2.75 A 125 V fuse, the 260 VAC varistor, the inrush thermistor and the semiconductors, together with the schematic and component layout.