The older Williams games
(Defender, Stargate, Robotron, Joust, Bubbles and Sinistar) have very
similar hardware inside. These machines have five PC boards:
CPU/Video- the main board, containing the CPU, RAM and video circuits
The game CPU is a Motorola 6809E. There are 24 4116 RAM chips, giving 48K
of DRAM, most of which is used for the video display (38K). There is also
a 1K by 4-bit CMOS SRAM that is battery-backed-up. This retains the game
configuration and high scores when the power is off. The video circuit
allows for 16 colors on the screen at once out of a total palette of 256 colors.
also for what is worth motorolla also make a simulator with exact replicas of most williams classic games (no not close too...exact copies) forgot that link. but here's the link to the original quote at the top of this post
http://coinop.org/kb_dl.aspx/kb/gametech/williamshwdescription.htmlis it just coincidence?