MOS Technologies designed an 8 bit microprocesor, the 6502, around 1975. Unlike the Intel 8080, it had very few registers. It was 8 bit with 16 bit address bus. Inside was one 8 bit data register (an accumulator), two 8 bit index, and an 8 bit stack pointer. It used thee index and stack registers effectively, with more addressing modes, including a fast zero-page mode that accessed memory locations from address 0 to 255 with an 8 bit address. This was pin for pin compatible with its Intel counterpart, but used lesser number of instructions.
The 6502 was used in the Apple
II, in BBC Microcomputer, ommodore, and Atari Personal Computers.
There is an expanded version of the 6502, the 65816.
Chip |
COMMODORE 6502 |
FAIRCHILD F8 |
GE-INTERSIL IN 6100 |
HITACHI 64180 |
INTEL 8080 |
INTEL 8085 |
Type |
Standard |
µC |
Standard 12 bit |
Standard |
Standard |
Standard |
Technology |
NMOS or CMOS |
NMOS |
CMOS |
CMOS |
NMOS |
NMOS |
No. Of instructions |
57 (NMOS)68 (CMOS) |
70 |
PDP8 |
50 |
69 |
71 |
Cycle time (µS) |
1.5, 3.0 |
2 to 13 |
2.5 to 11 |
0.12 to 0.1 |
1.3, 1.5, 2.0 |
1.3 |
Direct addressing (Bits) |
12 to 16 |
16 |
12 |
19 |
16 |
8 + 8 |
Registers |
3 |
1 + RAM |
3 |
-- |
7 |
7 |
Stacks |
Soft (8 bits) |
External sp |
-- |
-- |
Soft |
Soft |
Interrupts |
1 |
1 |
1 |
-- |
1 |
4 |
On-Chip |
|
|
|
|
|
|
|
Yes |
-- |
Yes |
Yes |
-- |
Yes |
|
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
64 |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
Yes |
-- |
-- |
|
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
-- |
-- |
8228 |
I/O lines |
-- |
16 |
-- |
-- |
-- |
2 |
Package (pins) |
28/40 |
40 |
28, 40 |
64 or 68 |
40 |
40 |
Power Supply (V) |
-- |
5, 12 |
5 |
5 |
+5, -5, +12 |
5 |
Second Source |
ROCKWELL, GTE |
MOSTEK |
HARRIS |
-- |
AMD, TI, NEC, NS, SIEMENS |
-- |
Remarks |
|
|
Static 10 mW |
Z80 instruction set compatible |
-- |
-- |
Chip |
INTEL 8048 |
MOTOROLA 6800 |
MOTOROLA 6809 |
NATIONAL NSC800 |
NATIONAL 32008 |
RCA CDP1800 |
Type |
µC |
Standard |
Standard 12 bit |
Standard |
Standard |
µC |
Technology |
NMOS |
NMOS |
NMOS |
CMOS |
NMOS |
CMOS |
No. Of instructions |
50 |
71 |
71 |
158 |
170 |
91/123 |
Cycle time (µS) |
2.5 |
2.0 |
1.3 |
1.6, 1.0 |
0.1, 0.17, 0.3 |
2.3 to 4.8 |
Direct addressing (Bits) |
-- |
16 |
8 + 8 |
16 |
24 |
16 |
Registers |
1 |
4 |
7 |
22 |
8 |
-- |
Stacks |
Hard (8) |
Soft |
Soft |
Soft |
Soft |
Soft |
Interrupts |
1 |
1 |
4 |
5 lines |
2 |
1 |
On-Chip |
|
|
|
|
|
|
|
Yes |
-- |
Yes |
Yes |
-- |
Yes |
|
1K |
-- |
-- |
-- |
-- |
0 to 2K |
|
64 |
-- |
-- |
-- |
-- |
0 to 64 |
|
Yes |
-- |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
-- |
-- |
-- |
I/O lines |
27 |
-- |
-- |
-- |
-- |
7 |
Package (pins) |
40 |
40 |
40 |
40 |
48 |
40 |
Power Supply (V) |
5 |
5 |
5 |
5 |
5 |
5 |
Second Source |
-- |
HITACHI, FUJITSU, THOMSON |
-- |
-- |
-- |
-- |
Remarks |
-- |
-- |
Enhanced 6800 |
Z80 instruction set compatible |
32-bits internal data |
-- |
Chip |
ROCKWELL 6500 |
SIGNETICS 2650 |
WESTERN DESIGN CP 1600 |
WESTERN DESIGN 65C802 |
ZILOG Z80 |
ZILOG Z280 |
Type |
Standard |
Standard |
Micro-programmed |
Standard |
Standard |
Standard |
Technology |
NMOS |
NMOS |
NMOS |
CMOS |
CMOS, NMOS |
CMOS |
No. Of instructions |
56 |
75 |
-- |
-- |
8080 + MANY |
-- |
Cycle time (µS) |
0.3, 0.5, 1.0 |
4.0 to 9.6 |
0.33 |
0.25 |
1.3, 1.6 |
0.1 |
Direct addressing (Bits) |
16 |
15 |
16 |
16 to 24 |
(16) |
16 |
Registers |
-- |
7 |
-- |
-- |
17 |
-- |
Stacks |
Soft |
Hard (8) |
-- |
-- |
Soft |
Soft |
Interrupts |
2 |
1 |
-- |
-- |
3 |
-- |
On-Chip |
|
|
|
|
|
|
|
-- |
-- |
-- |
Yes |
Yes |
Yes |
|
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
-- |
-- |
Yes |
|
-- |
-- |
-- |
-- |
-- |
-- |
|
-- |
-- |
-- |
-- |
Internal 8228 + Memory refresh |
-- |
I/O lines |
-- |
-- |
-- |
-- |
-- |
-- |
Package (pins) |
28/40 |
40 |
-- |
40 |
40 |
68 |
Power Supply (V) |
5 |
5 |
-- |
-- |
5 |
5 |
Second Source |
-- |
-- |
-- |
-- |
NEC, TOSHIBA |
-- |
Remarks |
6800 compatible |
-- |
PDP-11 |
16-bits internal data |
-- |
Enhanced Z80 |
