Connomore64: Cycle exact emulation of the C64 using parallel microcontrollers

by codewiz • 1 year ago

201 30 1 year ago

I love it. Ive been reviving a stack of 4 c64s i got untested for $285. I noticed CIA chip replacements cost 40-45 and was wondering if an Rpi pico could replace it! I'll bet they combined two CIAs into one. I'm curious if they repeat the typical 24+ pin bus (16 addr, 8 data, plus more control lines).

croemer• 1 year ago

Do CIA chip replacements come with a backdoor? </s>

genewitch• 1 year ago

Yes, via the frame buffer interface pins

robinsonb5• 1 year ago

Not directly - you'd need level shifters to handle the 5V signals in the C64. (The RP2040 isn't "officially" 5V tolerant - there are certain circumstances where you can get away with wiring some its inputs directly to 5V logic, but those circumstances exclude bidirectional IO.)

sunpazed• 1 year ago

Love this! The C64 introduced me to the world of computers as a kid. I still have that almost 40 year old machine in my collection, but I’m weary of failure every time I turn it on. This is somewhat better than the MiSTer as I can use physical peripherals with it. Great work!

Gergo• 1 year ago

The most common failure points in these old boxes are the capacitors and the power supply. Swap out all the caps and replace the original power supply for a modern remake and the 64 could last you another 40 years. :)

abhisek• 1 year ago

So cool! Things we would do to re-live the past. Not really into hardware but I remember trying to build an emulator for z80 just to learn how it work for old Sega games

Towaway692• 1 year ago

Can't wait until punchcards make a comeback ;)

Why isn't there an emulation of punch cards using eReaders!

Completely on your side, just wondering how far back do we go?

xobs• 1 year ago

There are usb-c paper tape readers: https://www.e-basteln.de/computing/papertape/overview/

They even work with phones!

TonyTrapp• 1 year ago

Completely on your side, just wondering how far back do we go?

The main difference is probably that many people had a C64 in their bedroom, so there's a lot of childhood nostalgia involved. Fewer people probably had a mainframe computer with punch cards in their bedroom. ;) Such emulation would probably be more interesting from a pure preservation perspective, and be less about nostalgia.

bmink• 1 year ago

Tbh it’s not just nostalgia (at least for me). That machine (and related machines) had such a unique combination of limitations and possibilities that 35 years on, I still find a lot of inspiration in code and optimizations that were/are being written for C64 and are directly or indirectly applicable to programming today.

8 bit CPU with 16 bit address space, a simple assembly language, most peripherals accessible by modifying bytes in memory, coupled with a desire to show off and one up each other produced an absolute treasure trove of programming tricks and techniques. Coders regularly produce(d) results that on paper were not possible on C64.

sandos• 1 year ago

Ohh, at first I was excited to see if this mean you could just replace parts of the C64 with some nice modern building blocks: I have a very old C64 that I don't want to cannibalize for parts that has a broken clock module. But this is not quite that. :)

rollcat2• 1 year ago

You may be interested in this: https://www.hackster.io/news/building-a-brand-new-c64-96e803...

rollcat2• 1 year ago

I love the sound of the SID chip, happy to find out about this project as well: https://github.com/frntc/SIDKick-pico

8 Bit Weapon are making some fantastic use of it:

https://8bitweapon.bandcamp.com/album/disassembly-language-a...

https://8bitweapon.bandcamp.com/album/modular-sidsation

LukHash also regularly features C64s in his kit:

https://www.youtube.com/watch?v=3JQkW6BgUYU

Share your favourite artists!

_the_inflator• 1 year ago

The best online SID Web player with access to HVSC and beyond can be find here:

https://deepsid.chordian.net/

The host and mastermind behind this artful resource is no other than:

JCH of Vibrants

Enjoy and have fun playing around with the player settings as well to tweak any tune available to your liking.

reaperducer• 1 year ago

The best online SID Web player with access to HVSC and beyond can be find here

I prefer local. Do you know of a good macOS SID player? I'd love to drag out some of my old files.

lttlrck• 1 year ago

8bit Weapon transports me back in time. Pure hypnostalgia.

eabeezxjc• 1 year ago

I am in favor of this solution. But let it not be closed. Let's also run fuzix.org on it .

wiz21c• 1 year ago

rewritten graphics rendering code (running 5-10 times as fast as the previous code while sacrificing some compatibility)

argh, too bad. If one goes the cycle-accurate way, then not doing everything accurate is a bit strange... I wonder why they made that choice...

fb03• 1 year ago

I found that design decision a bit odd as well, as the author states multiple times that he's interested in cycle-accurate emulation. When people go for a cycle-accurate emulator, they are purposely eschewing performance for accuracy. e.g. the Higan emulator which focuses on accuracy/code readability, but it's one of the slowest SNES cores out there (and it's fine)

chillingeffect2• 1 year ago

I took that to mean it takes less pico cpu power to reach the same cycle-accuracy.

Esp since there arent graphics routines in the c64 to speak of! There are no plot, screen clear, line, etc. Every program rolls its own.

As a joke a real freak could polyfill/hijack e.g $ffd2 output single char to cursor position in native pico code instead of 6502 to accel basic programs. That could be weird and phone to speed up all thise routines... but at that point just clock it all faster :)

gitroom• 1 year ago

Love how people still put so much effort into keeping old C64s going, makes me wanna fix up my own stash tbh.

bitwize• 1 year ago

I've long thought it should be possible to get timing-correct emulation by having multiple CPUs each emulate some component, rather than emulating everything on one CPU. It's cool to see this idea put into practice; the devil is always in the details.

Connomore64: Cycle exact emulation of the C64 using parallel microcontrollers

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