Information Technology Reference
In-Depth Information
In has been shown that a killer software application, or game, is required for the wide-
spread adoption of a new computer system. This killer application occurred for the Apple II
when Dan Bricklin developed the VisiCalc spreadsheet program. Unfortunately, for him, and
fortunately for others, such as Lotus and Microsoft, he never patented his technology. If he
had done this, he would have become a multibillionaire. Dan got the idea of the electronic
spreadsheet while he sat in a class at Harvard Business School. He designed the interface,
while his partner, Bob Frankston, wrote the code. The VisiCalc software ran on the Apple II
computer, and had a significant effect on the sales of the computer. It has since been the fa-
ther of all other spreadsheet programs, such as Lotus 123 and Microsoft Excel (Lotus even-
tually bought the rights to VisiCalc for $800 000 in 1985), and was released in 1979.
The Commodore PET 2001 was also based around the 6502 CPU, and had a simpler
specification (4 KB RAM, 14 KB ROM, keyboard, display, and tape drive), but it only cost
$600. In competition, and at the same price, Radio Shack developed the TRS-80 microcom-
puter. It was based around the Z80 processor and had 4KB RAM, 4KB ROM, keyboard,
black-and-white video display, and tape cassette, and sold well beyond expectations.
Microsoft expanded their market by developing Microsoft FORTRAN for CP/M-based
computers, and granted Apple Computer a license to Microsoft's BASIC.
1.3
8086/8088
The third generation of microprocessors began, in June 1976, with the launch of the 16-bit
processors, when Texas Instruments introduced the TMS9900. It initially used the TI 990
minicomputer. The processor never took-off as it lacked peripheral devices, and it was on
May 1978 that Intel released the 8086 microprocessor. This processor was mainly an exten-
sion to the original 8080 processor and thus retained a degree of software compatibility. Intel
first introduced the 4.77 MHz 8086 microprocessor, which had 16-bit registers, a 16-bit data
bus, and 29 000 transistors, using three-micron technology. It had a 20-bit address bus and
could thus access 1MB of memory. It had good performance at 0.33 MIPS and initially sold
for $360 (maybe a joke at the expense on the IBM System/360). Later speeds included
8 MHz (0.66 MIPS) and 10 MHz (0.75 MIPS).
IBM's designers, after discussions with Bill Gates, realized the power of the 8086 and
used it in the original IBM PC and IBM XT (eXtended Technology). It had a 16-bit data bus
and a 20-bit address bus, and thus has a maximum addressable capacity of 1 MB, and could
handle either 8 or 16 bits of data at a time (although in a messy way). Its main competitors
were the Motorola 68000 and the Zilog Z8000.
It was important for Intel to keep compatibility with 8080. The difficulty was that the
8080 used a 16-bit address (64 KB or 65 ,536 locations), whereas the 8086 would use a 20-bit
address bus, allowing up to 1 MB of memory to be addressed. Thus, the 8086 was designed
with a segmented memory, where the memory was segmented in 64 KB chunks. The 20-bit
address was then made up of a segment address, and an offset address.
In February 1979, Intel released the 8086 processor as follows:
The Intel 8086, a new microcomputer, extends the midrange 8080 family into the 16-bit
arena. The chip has attributes of both 8- and 16-bit processors. By executing the full set of
8080A/8085 8-bit instructions plus a powerful new set of 16-bit instructions, it enables a
system designer familiar with existing 8080 devices to boost performance by a factor of as
much as 10 while using essentially the same 8080 software package and development tools.
Search WWH ::




Custom Search