MITS 2SIO serial chip?

From: Ben Franchuk <>
Date: Mon Dec 17 05:28:00 2001

Richard Erlacher wrote:

> The 650x core is apparently known to be about 3300 gates, if you can go by their
> putative gate count. However, you can check 'em out for yourself. Google will
> turn up several. As you might expect, the Z80 core is quite a bit larger and
> runs somewhat slower. I don't think anyone's done the 650x core "right" yet,
> because most of the HDL's still are too big.

Lets say 3K gates. Lets also define a small FPGA is one that fits in a
84 pin
PLCC. The FPGA is used just for the CPU - no ram , rom , or I/O devices.
Looking at free-6502 as a guide.
it is really hard to tell just how many CLB's are used, but are just
over the
limit of what fits in small FPGA is what it looks like.
> I remember the trade (~1976-77) mag's telling us that the 6502 was <1/4 the size
> of the Z80 though they were in the same technology. The only way I can see that
> happening, aside from the vastly reduced internal resources that the 650x has,
> is a much slicker design.
I suspect this is because

1) All registers but the PC are 8 bit.
2) Instructions grouped into fewer internal states per clock.
  I think a z80 instruction could have 17+ states where a
6502 used up to 5 states.

Ben Franchuk --- Pre-historic Cpu's --
Received on Mon Dec 17 2001 - 05:28:00 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:33:40 BST