The C64 showed an similar effect as described in the original post. To to a full reset you had to turn it off, wait about 5 seconds and turn it on again. If you did not wait the RAM was at least partly preserved. The C64 had no dedicated video RAM, the VIC just read from regular RAM.
So if you did the power cycle quickly enough the screen was preserved.<p>Another effect of the screen RAM being regular RAM was that you actually could run programs in it while it was being displayed. You could watch a program run in the literal sense. This was often used by unpackers. The unpacker run in the screen RAM, filling the rest of the RAM. After its job was done the game started and filled the screen RAM with graphics destroying the unpacker.<p>EDIT: Found a video showing activity in the screen RAM of a C64. I&#x27;m not sure if this is the unpacker or this is really code execution, but it looks similar how I remember it.<p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=5nDzFsCEZT8&amp;feature=youtu.be&amp;t=92" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=5nDzFsCEZT8&amp;feature=youtu.be...</a>