The Apple II

Codename: ??
CPU: MOS Technology 6502
CPU speed: 1 Mhz
FPU: none
motherboard RAM: 4 k
maximum RAM: 64 k
number of sockets: n/a (RAM expansion via 1st expansion slot)
minimum speed: n/a
ROM: 12 k
L1 cache: n/a
L2 cache: n/a
data path: 8 bit
bus speed: 1 Mhz
slots: 8 proprietary
SCSI: none
Serial Ports: optional expansion card
ADB: none
Floppy: optional
HD: none
Display: 6 color at 280x192, 4-bit color at 40x48
Sound Output: built in speaker
power: ??
introduced: 1977
terminated: 1980

Built in 1977, the Apple II was based on Wozniak's Apple I design, but with several additions. The first was the design of a plastic case--a rarity at the time--which was painted beige. The second was the ability to display color graphics--a holy grail in the industry. The Apple II also included a larger ROM, more expandable RAM (4K to start), and 8 expansion slots. It had integer BASIC hard-coded on the ROM for easier programming, and included two game paddles and a demo cassette for $1,298. In early 1978 Apple also released a disk drive for the machine, one of the most inexpensive available. The Apple II remained on the Apple product list until 1980. It was also repackaged in a black case and sold to educational markets by Bell & Howell.

Pictures: Personal Computing Magazine, 11/84, Apple Museum


From: "Bill Dugan" (bdugan@interplay.com)
Date: Tue, Aug 18, 1998, 6:00 PM
To: glen@apple-history.com
Subject: Apple II

The Apple II series' 6502 processor could only address 64K of memory (both RAM and ROM combined). The ROM was located in the upper 12K, including AppleSoft BASIC and the Monitor. There is a clever story about this...

The 64K that the 6502 could address was arranged roughly like this:

48K: RAM
4K: Expansion cards
+12K: ROM
------------
64K total

So when it came time to introduce RAM expansion cards, what to do? The 6502 was already maxed out, addressing all 64K that it could possibly address.

Microsoft used a clever solution in their 16K RAM expansion card. Programmers could toggle soft switches to "switch out" the 12K of ROM and instead address 12K of RAM on the expansion card. Another set of switches would "switch out" 4K of the RAM on the expansion card for a second bank of 4K RAM.

So, an Apple II+ with a 16K RAM expansion card could indeed access 64K RAM, but you had to cut off access to the machine's ROM while doing so. Other memory cards appeared (I had a Saturn 128K card) that used about the same scheme, with lots and lots of switches to use that upper 12K of address space to, tortuously, add more and more memory, 12K at a time. The Apple //e's 64K expansion board even swapped out the entire address space of the 6502, essentially containing a separate Apple //e mapped out in the expansion board, and you'd flip back and forth between the two if you wanted to use the extra 64K.

bill

From: "Glen Hoag" (hoag@ro.com)
Date: Tue, Feb 9, 1999, 3:34 PM
To: corrections@apple-history.com
Subject: Apple II

The 16k RAM card, which Bill Dugan credits to Microsoft, was originally designed by Apple, in order to support the UCSD P-system, aka Apple Pascal. Perhaps Mr. Dugan is thinking of Microsoft's CP/M Softcard, which contained a Z-80 microprocessor, and allowed the Apple to run software written for the Digital Research CP/M operating system, though it's possible that Microsoft made a knockoff of Apple's card. Many clones were available, as the Apple card was initially available only with the Pascal software.

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