NMI and mockingboard - Githubissues

tomcw / mb-audit

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Closed drudru closed 1 year ago

drudru commented 1 year ago

Hi @tomcw

is there a reference that describes which mockingboards used NMI? How was a programmer to know which boards used only IRQ?

tomcw commented 1 year ago

Only "Sound/Speech I" used:

NMI for the 6522 at $Cn80 for the 6522's TIMERs (+ also with the AY-3-8913 attached).
IRQ for the 6522 at $Cn00 for the SC-01.

NB. NMI was a poor design choice, and probably why in the 2nd-generation Mockingboard A & C range Sweet Micro Systems just used IRQ.

How was a programmer to know which boards used only IRQ?

Old software would allow the user to select the type of Mockingboard and the slot.

drudru commented 1 year ago

Thx for your insights on this Tom 👍