Re: Hardware emulation of 6509 using 6502?

From: silverdr_at_wfmh.org.pl
Date: Thu, 15 Mar 2018 15:06:11 +0100
Message-Id: <8A351E44-F8C0-4F0C-9601-3B815CD5F68A@wfmh.org.pl>
> On 2018-03-15, at 13:55, smf <smf@null.net> wrote:
> 
>> ... IMHO all the narrow boards, including the above 250469 do the same, and sometimes poorly. They are emulating the real C64 with their "improperly" sounding SID and "sparking" CMOS VIC (plus others, less outside noticeable differences), trying poorly to emulate the real 6581/6569 respectively.
> You're entering https://en.wikipedia.org/wiki/Ship_of_Theseus territory there.

Me? :-)

> I don't see that using the logical fallacy of appeal to extremes helps.

Surely not. Just, when did I do that?

> The SID and VIC are different because of analogue effects which are different in the manufacturing processing.

Yes, MOS reimplemented them using different technology / manufacturing process. Does this make them emulate the original ("real") ones or does it make them being "real thing"? Hey, they even *completely* changed the PLA. They dropped colour RAM (as separate entity) later on, etc. etc.

> It would be hard to emulate those differences accurately with an FPGA.

As it was probably hard to emulate the original behaviour accurately with a different technology / manufacturing process.

> implementation: "the process of putting a decision or plan into effect; execution."

Right.

> Lots of people have implemented emulators. Some use CPU's, some use FPGAs. They are both emulators, like bananas and tomatoes are both fruit.

Again - if one takes e. g. Jim's PLA replacement, built with a CPLD and inserts it into his C64, will it become „emulation”? What if he does the same with some other chips? DRAM replaced with SRAM, SID replaced with the latest swinsid derivative, two voltages PSU, replaced with single voltage supply, ROMs replaced with flash, ... [*]  When will it stop being the real thing and start being the Theseus Ship... erm.. emulation? ;-) Please note also that some of those replacement may give experience closer to the "real C64" than the narrow boards do.

What if someone then combined all those replacements into a few CPLDs? What if he later moved it all to one FPGA, while still keeping full functionality? What if after having it proven to work with FPGA, he moved all of it to a mass-producable, non-reprogrammable IC?

> It might be inconvenient in a sales pitch to say that the fpgas are emulating a c64, if you've done a lot to rubbish emulators. However it's a better idea to focus on why using an fpga to emulate a computer is much better than using software on a computer running an OS. Unless you really want to lie to people.

If I design a new computer now and implement it using FPGA, will I have a computer or will I emulate a computer? What if for designing this new computer I use some pre-existing concepts?

You know, I see your point. I really do. It is just that I don't fully agree. Or maybe I rather draw the dividing line at a different level.

Last but not least both of us don't yet know what the "ultimate" experience is going to be...

* - all of the things I did to my poor C64 plus some more
-- 
SD!
Received on 2018-03-15 16:00:02

Archive generated by hypermail 2.2.0.