> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Chuck > Guzis > Sent: 14 July 2015 18:17 > To: gene...@classiccmp.org; discuss...@classiccmp.org:On-Topic and Off- > Topic Posts > Subject: Re: Reproducing old machines with newer technology (Re: PDP-12 at > the RICM) > > I'm missing something in this discussion, I think. > > HDL's (take your pick) are just programming languages like FORTRAN or C > with different constraints. What's the point of going to all the trouble of > doing an FPGA implementation of a slow old architecture, when pretty much > the same result could be obtained by running a software emulator?
I don't think this is true. Most of the software simulators don't run at anything like accurate speed ... > Neither > accurately reflects the details of the real thing--and there will always be > the > aspect of missing peripherals. I believe that you can get much closer with an FPGA... > > Perhaps the worst aspect of using FPGA is that this is a rapidly moving field, > so that the part you used to do your implementation 10 years ago > will no longer be available. That is very true, but there again the same can happen with Software. The Pegasus Simulator I use was written in TurboPascal and has kludges to get the speed right that just don't work on a modern PC > I've done a few designs using 5V CPLDs > (XC95xx series) not *that* long ago. Now they themselves are quaint > examples of obsolete hardware. You can't win. > > You can move software-only simulators quite easily, but I'm not as sanguine > about FPGA designs. > See Above > And you still don't have the peripherals. I suppose one could emulate a > Univac Solid State machine in FPGA, but what would one do about the all- > important drum coupled to the card reader and printer. Has anyone rolled > out a design for a DIY 1403 printer? When I have finished the Calcomp Plotter.... > > I've run the Cyber emulator as well as various SIMH emulators from time to > time, but it's just not the same as the real thing--it's not even remotely the > same. I have used Hercules with a real 3270. Its not bad but Laurence Wilkinson's 360 in FPGA wih a real Selectric Typewrite is much better:- http://www.ljw.me.uk/ibm360/Saga.html > > --Chuck > Dave
