Re: Nibz processor @ <570 MAXII LEs (16 bit generic specified), 20MHz

On Mar 13, 9:02 am, Herbert Kleebauer <k...@xxxxxxxxx> wrote:
rickman wrote:
I am still looking for a good small soft-core, and well it seem
not to exist...

I seem to recall that you were trying to find a bit serial CPU that
would be the smallest possible in an FPGA.

I don't think it is possible to make a serial CPU smaller than
a parallel one. Here is a 16 bit CPU with interrupt support
built with only 65 flip-flop's. If you reduce the size to
12 bit (3 kbyte memory space) you can even save 12 flip-flop's.

http://www.bitlib.de/pub/mproz/mproz3_e.pdf (with internal RAM)http://www.bitlib.de/pub/mproz/mproz2a.pdf (with external RAM)

schematics in the zip files:

http://www.bitlib.de/pub/mproz/

Are you saying that this processor can't be made smaller? Registers
can be stored in memory rather than FFs. By processing the registers
serially the logic can be greatly reduced at the expense of more
control logic. I don't see how you can say that any machine can't be
reduced by replacing

BTW, I don't know why you are stating the FF count as if this were a
good measure of design size. Most designs in FPGAs use more LUTs than
FFs. The logic of this beast is likely With 65 FFs this may well be
designed for a CPLD which has more capable logic with each FF. But
few of those parts have any ram. That means you need external ram and
I don't consider that a "simple" or small design. Still, I have to
say, this is one goofy processor. It does everything in memory and
only has five instructions. Is this thing really of any use other
than academic?

Rick
.

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