BMOW is a Custom CPU Design

• Like your PC’s Pentium, but much simpler

• Closest cousin is the MOS 6502 used in the Apple II, C-64, and Atari VCS

=

BMOW is a Custom CPU Design

• Three 8-bit data registers

• 24-bit address size• 64 KB segments• 12 addressing modes• Microcoded design• From 1 to 16 clocks

per instruction

BMOW is Hand-Made

• Built from 1970’s and 80’s era electronics• 50 simple chips are connected to form the CPU

– AND gates, counters, multiplexers, registers– Simple GAL programmable logic

BMOW is Hand-Made

• Chips connect by wires under the system board• Wires are hand-wrapped around the pins• About 1250 wires total, 2500 wraps

BMOW is a Complete Computer

• PS/2 Keyboard input• Text LCD display• Optional USB

connection to PC• VGA video output• Three-voice audio

BMOW Video System

• Custom video circuitry• 512 x 480 max resolution• 256 simultaneous colors• 16 different video modes• Video mode can change

on every scan line• Mixed text and graphics

modes• Standard VGA output

BMOW Software Tools

• Bootloader• Simulator and

debugger• Microcode

assembler• Program

assembler

BMOW Specs Comparison

Name Year CPUClock Speed

Data Size

Address Size

Memory I/O Sound Max Res.Max Colors

Apple II 1977MOS 6502

1 MHz 8 16 48 KBcassette, floppy disk

1 software voice

280 x 192 16

Atari 800 1979MOS 6502

1.79 MHz 8 16 48 KBcassette, floppy disk

4 hardware voices

320 x 192 16

Commodore 64 1982MOS 6510

1 MHz 8 16 64 KBcassette, floppy disk

3 hardware voices 320 x 200 16

IBM PC 1981Intel 8088

4.77 MHz 8 / 16 20 256 KBcassette, floppy disk

1 software voice 640 x 200 16

BMOW 2009 custom 2 MHz 8 24 512 KBserial over USB

3 hardware voices

512 x 480 256

BMOW Project Summary

• 1½ years to build• 2500 hand wire wraps• $500+ worth of parts• Why? I don’t know.