of Microprocessors

SOME REAL ApPLICATIONS
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AUDIO INPUTS
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Fig. 19-13. Block Diagram of DMX-1000
processor" that is like a general-purpose computer but has an instruction set,
register complement, and architecture optimized for repetitive sample
calculation applications. It is the repetition (which makes pipelining
possible) and specialization that allows such a machine to run synthesis
calculations 5-50 times faster than a general-purpose computer of the same
complexity and logic curcuit speed.
An example of this approach is the DMX-lOOO Signal Processing
Computer from Digital Music Systems, which is pictured in Fig. 19-12.
This commercial, programmable, digital signal processor is actually an
outgrowth from work done in the Electronic Music Studio at MIT. Packaged
in a moderately small rack-mount enclosure, the DMX-lOOO has a universal
8-bit parallel interface that can connect to almost any computer. Most users,
however, drive it from a DEC PDP-Il, primarily because most of the support
software available is for that computer.
The DMX-lOOO uses what is called a "Harvard architecture," in which
the program memory is completely separate from the data memory. The
simplified internal block diagram in Fig. 19-13 reveals that there are actually
three memories: a 256 word X 32-bit program memory, a 4K X 16 data
memory, and a 64K X 16-bit delay memory. The difference between the data
and delay memories is that the latter is much slower (six machine cycles
versus one) and is also optional. It is typically used to implement signal
delays in reverberation simulation and digital filtering programs. The host
computer can read and write any of the memories either continuously while
the DMX-lOOO is stopped or once each sample period while it is tunning.
This allows programs to be loaded into the program memory and parameters