View Full Version : Apple II

January 17th, 2011, 07:37 AM

The Apple II (Also known as the Apple ][), was the 2nd of the Apple series, following the Apple Computer, (now known as the Apple I), in 1977. It and its successors in the line the best selling computers of their time until the release of the IBM PC in 1983, and Apple's No.1 product until the release of the Macintosh computer in 1984.
thumb|right|An Apple ][ with monitor and two Disk ]['s
The Apple ][ had BASIC in ROM, as did many other computers.
6502 CPU at 1MHz
4KB of RAM
Cassette Interface
Joystick Port
Composite video output
52 key keyboard (45 character keys.)
8 Expansion Slots (numbered 0 to 7)

Standard Accessories
16K Language Card (slot 0)
80 Column Card (not a //e Extended 80 Column Card)
Shift Key Modification
Disk II Controller (slot 6 for first is standard)
Disk II Disk Drives (up to two per controller)
Mockingboard Sound Card
Serial I/O Board
Centronics Printer Interface (e.g CardCo or Orange Micro)
Memory up to 64KB

Operating Systems
Disk BASIC ("Applesoft BASIC")
Apple DOS up to up to version 3.3
PRODOS up to version 1.9

The keyboard is very basic, providing only upper case letters, numerals, and a few symbols. It was missing many common symbols used in various programming languages. Languages for the Apple II often allowed alternate character combinations to replace such characters as curly braces, square brackets, etc. There were also third party programs that would perform character substitutions, and upgrades that would add features to the keyboard or replace it.
Disk Boot
The original Apple II would not boot off a floppy automatically. When the Apple II+ was released, upgrade ROMs became available for the II that provided automatic booting from the floppy at reset or power-on.
Apple II+, largely the same but with enhanced ROMs.
Apple IIe, many improvements including redesigned keyboard and support upper and lower case. Displays "Apple ][" at boot.
Apple IIc, portable system based on the 65C02 processor with built-in peripherals including a 5.25" floppy drive.
Apple IIe Enhanced, an update to the IIe with 65C02 CPU, updated video, BASIC, and monitor ROMs, allows expansion to 128K of RAM, and new video modes. Displays "Apple //e" at boot.
Apple IIgs, Clean-slate redesign of the Apple II around a 65816 8/16 bit CPU capable of running at higher speeds, new video controller and sound chip provide built in multimedia capabilities rivalling those of the latest 16 bit computers of the time.
Apple IIc Plus, 4MHz update to the IIc with 3.5" floppy drive expadable to 1MB RAM.
Apple II Compatibility Card, an Apple II emulation card for Macintosh, available in several forms for the PDS slot in certain models of Mac. Provided Apple //e level functionality.

The success of the Apple II spawned many clone systems. Here are some representatives of the lot:
Pineapple, a clone of the Apple II and later the II+.
Syscon 2, a clone of the II+ with upper/lower case and 48K standard.
Laser128, IIc clone with adjustable processor speed and better compatibility with the //e than the IIc for much software.
Franklin Ace 100, a nearly exact copy of the Apple II+, including direct copies of Apple's ROMs.
MicroProfessor II, a Chinese Apple II clone with many differences. No text mode, Chinese BASIC, 48K standard.


February 13th, 2012, 05:18 AM
Apple II didn't have a "Power on reset" circuit. You had to press the "reset" button to get it to start. Apple realised the drawbacks to that and added a power on reset circuit. For customers with no "Power on reset" circuit, fitting a DiskII floppy disk driver card also solved the problem, as the DiskII card was also fitted with a "Power on reset" circuit. ANY Apple II will automatically boot up if fitted with a DiskII card, even if no drives are plugged into the DiskII card.

The Apple II has three rows of eight RAM chip sockets fitted. Originally, the configuration headers fitted to each row were for 4Kbit RAMs (8 per row to store bytes).
The smallest amount of RAM therefore was 4Kbytes. Fitting 8 more 4Kbyte RAMs gets you 8Kbytes, and a full motherboard (3 rows of RAMs) gets you 12KBytes.
When 16KBit RAMs became available, Apple fitted 16K configuration blocks. Interestingly enough, some mixing and matching was possible, so 16K, 20K, 24K, 32K and 48K
were all possible. The "MAX RAM" 48KByte memory could be further enhanced using a "Language Card" which was fitted with a further 16KBytes of RAM.

Apple were very sensible in fitting every chip in a socket. It helped when fixing hardware faults. Unfortunately, the sockets themselves were the cause of a lot of the problems.
If you take out a chip from a socket, you will see a row of black dots, one dot per leg, which is where the socket touches the leg of the IC. We only ever sorted this by removing every IC socket (lever the plastic bit off the individual metal pin sockets, then unsolder the metal pin sockets, one at a time) and fitting good quality turned pin sockets.