🚀 go-pugleaf

In article <3310@uceng.UC.EDU> schriste@uceng.UC.EDU (Steven V. Christensen) writes:
>Let's say I want to build come computer-based device, OK, and let's
>say I want to interface this to an IBM-PC, OK. I want that the
>PC could be able to download into the memory of this project,
>and then kick the processor to start executing.

The quick answer is that dual-porting memory is a royal pain and tends to
be costly in chip count.  Life is much simpler if only one processor does
memory accesses.  Unless the project CPU, or some other part (e.g. the
dynamic-RAM controller) is unusually helpful, much the easiest approach 
is to have the project CPU start running out of a ROM, and have it pick 
up the data from somewhere and stuff it into memory for you.

>I have seen some chips called "dual-ported something-or-other", but
>have not investigated. Are they usable (and simple) solutions?

Usually not.  There are some dual-ported memory chips, but they are
small in capacity, large in board area, expensive, and sometimes tricky.
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1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu