emulating an Apple II+ in an FPGA

Keith Monahan keithvz at verizon.net
Wed Jan 6 10:27:06 CST 2010


Brian Lanning wrote:
> I noticed that there's an article in the december circuit cellar that
> talks about emulating an Apple II+ in an FPGA.  It was an interesting
> article, although I only understood about 20% of it.  As a software
> guy though, the hardware "code" has me interested.  Maybe this would
> be an easier and less time-consuming way for me to learn about
> hardware.
> 
> brian

Brian,

I've got to subscribe -- sounds like a neat article.  I recently 
subscribed to Nuts and Volts, and I like the fact that you get access to 
all of the back issues back to like 2004 for free included w/ your 
subscription.

The whole retro-computing thing in an FPGA floats my boat.  Very neat 
stuff.  Lots of people have been reverse-engineering or duplicating the 
functionality of these old custom chips which is fantastic.  Plus I love 
how it scales.  Got two custom chips? 10 custom chips?  The logic will 
fit into a small FPGA.  And then throw the soft-core processor onto the 
same FPGA and you have the system-on-a-chip idea.  And there's little 
wiring to do because everything is internal.

As far as less time-consuming goes, I wouldn't count on it.  I've had an 
FPGA board for awhile and there is a learning curve there.  I've enjoyed 
the time I've spent on it, but like anything else, there is a fair bit 
of complexity if you hope to understand how everything works.  The 
installed Xilinx(in my case) ISE software is huge, and requires a decent 
machine to give reasonable performance.  The fact that many tools are 
separate programs, while (mostly) launched from the same place, leads to 
minor integration problems.  Like tools that are command line only, and 
need 8.3 filenames.  Or other tools that can't handle spaces in 
filenames (like "Documents and Settings", ie)  And then there's 
documentation, which is mostly good, but BIIIIG.  Like 600 pages for a 
memory controller.

I'm not trying to sway your decision.  Playing w/ this hardware is lots 
of fun --- just want to set your expectations accordingly.

Keith



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