On Sep 22, 2023, at 3:59 PM, Martin Bishop via cctalk
<cctalk(a)classiccmp.org> wrote:
100% disagree, Verilog and SV are bad tools - very easy to do a bad job with - penknife
grade.
Verilog however is very c like in that it is untyped and prone to all the consequent tar
pits; see above.
VHDL is a good tool which is typed and like the Algol family of languages precludes many
follies.
The 2008 flavor, which is where the tools are curently, is not as pedantic as the older
standards '97 & '83.
I only know VHDL but I had heard that Verilog is C-like, and yes, C offers an unusually
large set of tools to shoot yourself in the foot with. So it wouldn't surprise me
that Verilog does likewise, which certainly means that it would be the option to avoid.
VHDL is very clearly based on Ada, which like Pascal and ALGOL takes data types seriously
rather than only as suggestions the way C does. I've built some very large designs
with VHDL, but not because I actually wrote that much code -- a lot is generated code
produced from wire lists. But I did write all the models of all the 6000 modules, which
does add up.
Apart from vendor tools for producing bits for particular FPGAs, you can also find VHDL
simulators that just simulate a model but don't deliver it to a particular chip. I
use GHDL, which is part of the GCC toolset. Yes, a VHDL compiler, interesting. Among
other things, it allows you to link bits in other languages, so I can take device models
from the DtCyber emulator and attach them to a VHDL-modeled I/O channel.
On FPGAs, it's worth checking what the story is for vendor tools. Some devices and
vendors try to suck large sums of money out of you for them; Lattice is an example. Even
for small devices (like the ispLSI2032 I used years ago) that expense adds up rapidly. I
think they have become somewhat more reasonable now, offering free tools for the smaller
devices. I know Xilinx does so, and "smaller" covers a surprising amount of
capacity these days. I'm pretty sure a PDP-11 model would fit fine in one of those
"free tool" devices, though a CDC 6600 probably won't.
paul