On Fri 01 Apr 2022 at 14:30:13 -0500, Jim Brain wrote: > http://www.zimmers.net/anonftp/pub/cbm/faq/trivia/cbm-trivia-08.txt > (question $07b) from that: "We early PET/CBM freaks knew, from playing music, that there was something wrong with the 6522's shift register: it interfered with other functions. The rule was: turn off the music before you start the tape! (The shift register was a popular sound generator)." Do we already know why the shift register interfered with the tape? and, to remind people, do we already know why pressing the < button while loading / scanning the tape for something to load would print < characters to the screen if there was a signal on the tape? Neither are emulated in VICE (I think I tried it once) so it isn't something that trivially occurs... Also, Compute #3, march/april 1980, mentions that sound doesn't work if you have C2N #2 plugged in. Page 88: "NO CB2 SOUND? Larry Isaacs Some of you may have been unable to get the CB2 Sound, described in last month's RAMBLIN', to function. Fortunately the most likely cause has a very simple solution. Unplug the external cassette from the rear of your PET. Having an idle cassette plugged into that cassette port grounds the CB1 line on the 6522 IC in the PET. Grounding CB1 unfortunately stops the shifting of the shift register used to generate the CB2 Sound. I also checked a Synertek 6522 (PETs use MOS Technology) and found that it had the same problem. It appears that this is inherent in the design of the 6522, so keep it in mind when using the shift register for output. -Olaf. -- ___ "Buying carbon credits is a bit like a serial killer paying someone else to \X/ have kids to make his activity cost neutral." -The BOFH falu.nl_at_rhialto
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