Apple ][ Plus

The Apple II Plus is an upgraded version of Apple's first mass produced computer the Apple II. It was released approximately 2 years after the release of the Apple II in June of 1979. The computer is actually the same as it's predecessor with a few 'enhancements'.

One improvement was the amount of RAM on the system board. It came standard with 48 kilobytes of RAM, on the mother board, and could be expanded to a full 64 kilobytes by inserting a 16 kilobyte expansion card into slot 0 and using a bank switching technique to trick the MOSTEK 6502 processor into seeing it.

This was necessary because the 6502 processor is an 8 bit chip with only 16 address lines which limits it to be able to address only 65,536 (64k)address locations. And since the Apple II Plus uses 16 kilobytes of those locations to store it's ROM instructions, only 48 kilobytes of space is left for RAM usage. But the engineers at Apple came up with this neat little trick of swapping 16k blocks of RAM into the address area reserved for ROM as needed to give the illusion that there is a full 64k of RAM available for programming.

The ROM was rewritten and gone was the hand assembled BASIC written by the man who invented the Apple II, Steve Wozniak, replaced with a new integer BASIC written by a small software company owned by..... [ you hard core Apple types should look away now :-) ] ...Bill Gates. An auto-starting routine was added to the ROM to speed up booting and a spring was put under the reset key to solve that little problem that must have annoyed the early Apple users who would accidentally hit the reset key and lose hours of typed work.

This Apple II Plus is one of two working models I have in my museum. I was able to put them together from three broken ones and some spare parts acquired from Ebay auctions. I would like to thank Brandon Cobb, Ron Watson, and Robert Ackermann for their contributions to this exhibit.

System Architecture		Memory
Microprocessor	MOSTEK 6502	Standard on system board	48k
Clock speed	1.023 MHz	Maximum on system board	48k
Bus type	Apple Proprietary	Maximum total memory	64k using plug in board
Data bus width	8-bit	Memory speed and type	200ns dynamic RAM
Address bus width	16-bit	System board memory socket type	16 pin DIP
Interrupt levels	N/A	Number of memory module sockets	24 socketed
DMA channels	N/A	Memory used on system board	TMS4116-20
Standard Features		Disk Storage
ROM size	16k	Internal disk and tape drive bays	none
Optional math coprocessor	no	Standard floppy drives	tape or 5.25 Floppy
Parallel port type	none	Optional floppy drives:	up to 2 external
RS232C serial ports	none	* 5 1/4 inch 143k	yes
Mouse ports	internal I/O socket	* 5 1/4 inch 1.2MB	no
UART chip used	N/A	* 3 1/2 inch 720k	no
Maximum speed	N/A	* 3 1/2 inch 1.44MB	no
CMOS real time clock	no	* 3 1/2 inch 2.88MB	no
CMOS RAM	no	Hard disk controller included	no
Video & Graphics		Sound
Graphics Processor	uses CPU	Sound Interface device	uses CPU
Screen size - Col x Rows	40 x 24	Sound generation	tone output to speaker
Resolution - Colors/High	6 / 280 x 192	ADSR capable	no
Resolution - Colors/Low	16 / 40 x 48
Max colors	16	Programming language
Sprites or Missiles	none	Built in language	Applesoft BASIC
		Built in M L monitor	yes
Expansion Slots		Keyboard Specs.
Total adapter slots	8	Number of keys	52
Number of 8/16/32 bit slots	8 / 0 / 0	Upper/lower case	yes / no
		Keyboard cable length	N/A
Physical Specs.		Environmental Specs.
* Height	4 1/4 inches	Operating voltage @ 60 Hz	120 VAC
* Width	15 1/4 inches	Maximum power supplied	60 WATTS
* Depth	17 3/4 inches	Power supply output - volts	+5V/-5.2V/+11.8V/-12V
* Weight	11.5 pounds	Power supply output - amps

Introduced	June 1979
Discontinued	January 1983
Release Price	$1195