VCF Build-It-Yourself Workshops - test-drb@ccmp.vtda.org

3 Oct 2006

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Subject: Re: VCF Build-It-Yourself Workshops
   From: "Chuck Guzis" <cclist at sydex.com>
   Date: Mon, 02 Oct 2006 15:31:28 -0700
     To: cctalk at classiccmp.org

On 10/2/2006 at 2:43 PM David Betz wrote:

 I would *love* to assemble an FPGA kit that
allowed me to experiment  
with various classic architectures (and maybe some modern ones!).  
Sign me up if you decide to have one! 
Golly, folks have been doing this for quite awhile.  The XESS kits seem to
be very popular.  There was/is even a fellow who was offering a
pin-compatible Z80 replacement implemented in FPGA.

Here's one of the lists I've found:

http://members.optusnet.com.au/jekent/FPGA.htm

What's not really clear to me is what the practical difference is between
implementing a classic CPU in FPGA and writing an emulator for on to run on
a PeeCee.   
That depends on many things.  An emulator for a PC might be a microprogrammed
archetecture for a PDP-5 which is a sequential logic machine. With real logic 
you have to deal with mudane and annoying things like two registers accessing 
a single bus.  From my point of view doing a classic in FLGA is convenient
as your not tied ot a PC but it's still more of a software exercise than real
random logic.

...
 As someone on the list has mentioned, it's really
the old peripherals that
are the interesting bit. 
That because you have to interact with the physical world. Often that requires
much more than a bit of logic to fly. 

Allison