Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!microsoft!brianw From: brianw@microsoft.UUCP (Brian WILLOUGHBY) Newsgroups: comp.sys.apple2 Subject: Re: GS Sound Message-ID: <60234@microsoft.UUCP> Date: 3 Jan 91 02:14:25 GMT References: <6292@crash.cts.com> <41391@ut-emx.uucp> <90349.002915AABENSON@MTUS5.BITNET> Reply-To: brianw@microsoft.UUCP (Brian WILLOUGHBY) Organization: Microsoft Corp., Redmond WA Lines: 40 AABENSON@MTUS5.BITNET writes: >As a note to what somebody or other said about 8 channels (this junky system >won't let me quote), yes, I also read that. The Ensoniq chip itself is made >for 16 channels -- probably for that MIDI stuff. Anyway, on the IIgs, only >eight of those are supported. Current stereo cards, such as the MDIdeas card >and Sonic Blaster, send all the even numbered channels to one side and the >odds to the other. > >- Andrew. I believe that you are confusing oscillators or wave channels with actual output channels. The Ensoniq chip has the capability for 32 oscillator channels, where each channel is capable of outputting a distinct sequence of bytes from DOC memory. These are generally programmed in odd/even pairs (a feature supported by the hardware on the chip). Each oscillator can be sent to one of 8 output channels by programming a 3 bit value (this is based on memory of the GS docs and also from 8 output circuits for the Ensoniq Mirage, which uses the exact same DOC chip). All 32 channels can be sent to one output channel, or they can be programmed to go their own way. Mixing of the oscillators which are sent to any single output channel is accomplished by time multiplexing, but you can't have more than 8 outputs. The 3 bit output address appears on the pins of the DOC hip at the exact moment a particular oscillator is converted from digital to analog. The GS ignores these address bits, which results in all output channels being mixed into one signal by time modulation. Most stereo cards ignore the most significant address bits, but use the LSB to cause all odd output channels to be mixed to the one output channel (i.e. left), and the even output channels go to the right (this could be reversed, but who cares at this point). Brian Willoughby UUCP: ...!{tikal, sun, uunet, elwood}!microsoft!brianw InterNet: microsoft!brianw@uunet.UU.NET or: microsoft!brianw@Sun.COM Bitnet brianw@microsoft.UUCP