<story><title>Reverse engineering the 76477 “Space Invaders” sound chip from die photos (2017)</title><url>http://www.righto.com/2017/04/reverse-engineering-76477-space.html</url></story><parent_chain></parent_chain><comment><author>8bitsrule</author><text>1978 was very early in the &amp;#x27;personal computer&amp;#x27; era. I&amp;#x27;d guess that the use of a VCO was modeled after early synthesizers like the Moog. (It used a 1-volt per octave scheme ... changing the external voltage input from 2 to 3 volts moved pitch up an octave.)&lt;p&gt;The 76477 &lt;i&gt;could&lt;/i&gt; take an external voltage (up to 5v) (Pin 16 via J2) for pitch - maybe the design&amp;#x27;s intent was to be able, when needed, to inexpensively generate external voltages, e.g. through a pot. The much-more powerful General Instrument AY-3-8910 arriving in 1978 sank any hopes the 76477 had.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;General_Instrument_AY-3-8910&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;General_Instrument_AY-3-8910&lt;/a&gt;</text></comment>
<story><title>Reverse engineering the 76477 “Space Invaders” sound chip from die photos (2017)</title><url>http://www.righto.com/2017/04/reverse-engineering-76477-space.html</url></story><parent_chain></parent_chain><comment><author>jbverschoor</author><text>I love this kind of stuff. I’m always amazed about how small we can operate.</text></comment>