[Coco] Fwd: Re: FPGA VS Software Emulators

[Joel Rees]

On Wed, Jul 26, 2017 at 4:46 PM, Walter Zambotti <zambotti at iinet.net.au> wrote:
> Mark
>
>>A cheap way to start is using a simulator; you can see your signal waveforms graphically and it's
>>much easier to experiment and debug. If I'm writing a complex self-contained module I generally
>>simulate it first in a simple testbench.
>
> Simulator?
>
> A software simulator for the FPGA device?
>
> Would the simulator be sufficient to actually execute the CoCo fpga projects (minus daughter boards)?
>

Well, yes, but ...

Unless the software which compiles the Verilog or VHDL source code can
recognize the definitions of the registers and the ALU functions, etc.
and optimize them heavily, you're going to have each bit of a register
being updated separately and things like that.

I'd expect that current versions of the FPGA simulators can optimize
some, but not even close to all, so it's going to be at least another
order of magnitude slower than VCC or xroar, which are coded
specifically to emulate the 6809's registers and functions.

There are, I believe, open source tools that simulate FPGAs. You might
find one and try some simple definitions of flip-flops and such to get
a better idea of what is happening. There's a list on this Wikipedia
page:

https://en.wikipedia.org/wiki/List_of_HDL_simulators

At least one of those is in the debian repositories, so, if you run
debian or ubuntu or such, it's just an apt-get away.

-- 
Joel Rees

One of these days I'll get someone to pay me
to design a language that combines the best of Forth and C.
Then I'll be able to leap wide instruction sets with a single #ifdef,
run faster than a speeding infinite loop with a #define,
and stop all integer size bugs with my bare cast.
http://defining-computers.blogspot.com/2017/06/reinventing-computers.html

More of my delusions:
http://reiisi.blogspot.com/2017/05/do-not-pay-modern-danegeld-ransomware.html
http://reiisi.blogspot.jp/p/novels-i-am-writing.html