norman@d.cs.okstate.edu (Norman Graham) (09/27/90)
How does the SID get its info to the Mac without overrunning
the serial ports? It samples 22K 8bit samples per second, but
without compression it would seem to require a data transfer
rate of 176Kbps. What am I missing here?
--Norm
--
Norman Graham <norman@a.cs.okstate.edu> {cbosgd,rutgers}!okstate!norman
The opinions expressed herein do not necessarily reflect the views of
the state of Oklahoma, Oklahoma State University, OSU's Department of
Computer Science, or of the writer himself.rosen@cs.utexas.edu (Eric Carl Rosen) (09/28/90)
In article <1990Sep27.165443.2923@d.cs.okstate.edu> norman@d.cs.okstate.edu (Norman Graham) writes: >How does the SID get its info to the Mac without overrunning >the serial ports? It samples 22K 8bit samples per second, but >without compression it would seem to require a data transfer >rate of 176Kbps. What am I missing here? > >--Norm This puzzled me as well until Mike Ciholas kindly explained. The Macintosh serial ports can be externally clocked at data rates far higher than the available internal clocking rates. The clock is generated by the SID and drives both the ADC and the serial port (pin 1 -- HSO). --Eric
norman@d.cs.okstate.edu (Norman Graham) (09/28/90)
From article <12956@cs.utexas.edu>, by rosen@cs.utexas.edu (Eric Carl Rosen): > In article <1990Sep27.165443.2923@d.cs.okstate.edu> norman@d.cs.okstate.edu (Norman Graham) writes: >>How does the SID get its info to the Mac without overrunning >>the serial ports? It samples 22K 8bit samples per second, but >>without compression it would seem to require a data transfer >>rate of 176Kbps. What am I missing here? > > This puzzled me as well until Mike Ciholas kindly explained. The Macintosh > serial ports can be externally clocked at data rates far higher than the > available internal clocking rates. The clock is generated by the SID and > drives both the ADC and the serial port (pin 1 -- HSO). Oops... silly me. I forgot that the serial ports can talk at up to 1Mbps when clocked externally. After all, we're talking about the 'virtual bus' (tm) from the original Mac 128K. They used to hang hard disks off this thing. Sorry for the memory lapse. --Norm -- Norman Graham <norman@a.cs.okstate.edu> {cbosgd,rutgers}!okstate!norman The opinions expressed herein do not necessarily reflect the views of the state of Oklahoma, Oklahoma State University, OSU's Department of Computer Science, or of the writer himself.
russotto@eng.umd.edu (Matthew T. Russotto) (09/28/90)
In article <1990Sep27.165443.2923@d.cs.okstate.edu> norman@d.cs.okstate.edu (Norman Graham) writes: >How does the SID get its info to the Mac without overrunning >the serial ports? It samples 22K 8bit samples per second, but >without compression it would seem to require a data transfer >rate of 176Kbps. What am I missing here? That the serial ports can in fact run that fast. (remember, Appletalk speed is faster than that-- I'm sure it takes a lot of processor time, especially on slow machines, but it is possible) -- Matthew T. Russotto russotto@eng.umd.edu russotto@wam.umd.edu .sig under construction, like the rest of this campus.