GUBBINS@RADC-TOPS20.ARPA (02/14/84)
From: Gern <GUBBINS@RADC-TOPS20.ARPA> Russ (and All), I looked over the DRC stuff you send Wolf. Thanx much. My previous concerns/guesses were correct. DRC is no longer selling the board. The device completely violates the IEEE-696 S-100 standard for bus line loading. To correct this would lead to a major redesign, hence they probably choose to just drop the product. The maximum the device can be driven at is 4MHz and it inserts 2 I/O wait states to do just that. My design is radically different and can work in a 5 MHz Z-100 without adding any I/O waits (Do note that the Z-100 does add one on its own). The DRC board would not work in my Z-100, so my design approach is the only way for me. This week I am going to see if I can extend my design to double that of the current 3 voice, 2 I/O design and not violate anything, or screw up the timming. I think I can do it and use 3 less ICs!!! And I will be able to play all of the piano sheet music to Star Wars Main Theme (requires 5 channels), I currently had to drop the Bass Clef notes - still sounds excellent. I'm going to take your suggestion and drop the I/O multiplexing which will yield a cleaner more uselful device. Cheers, Gern -------