[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: How does the ZIP chip work?



sicklittlemonkey wrote:
What am I missing here?


Nothing. It must have had a cache, and did. ;-)
Early accelerator cards cached all of RAM, I think.
Apple copied the ZIP design for the //c+. (Right guys?)

What I would like to know is the write-back policy for the cache.
I'm guessing that graphics writes were propagated immediately.
That could be tested by running some code in displayed memory.

It's a strict write-through cache.  This is necessary since the
tag RAM does not contain "dirty" bits.

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."