Thankful MachineAug 8, 2023

And there you go! My #68k #homebrew computer is running at 8MHz!​

I thought for a moment that I had messed something up, but of course it had to be the ROM write. `srec_cat` is your friend.

In the scope shot, top to bottom, we have CLK, /AS, and A0. A sort of "free running" mode, all zeroes in the ROM, i.e. ori.b #0,d0. It happens to work with the exception table and all of that.

Now, on to write a test program and make it say hello over serial! ​

There are so many wires in this thing, I can hold it up like a pizza slice without it bending. ​

#retrocomputing #m68k

Show threadAndreas (82mhz)
@thankfulmachine That looks amazing! I'm impressed and slightly jealous ;)
Aug 15, 2023 at 11:22pmWeb
Show threadThankful MachineAug 16, 2023
@82mhz Shucks. Thank you!
×
Thankful MachineAug 8, 2023

And there you go! My #68k #homebrew computer is running at 8MHz!​

I thought for a moment that I had messed something up, but of course it had to be the ROM write. `srec_cat` is your friend.

In the scope shot, top to bottom, we have CLK, /AS, and A0. A sort of "free running" mode, all zeroes in the ROM, i.e. ori.b #0,d0. It happens to work with the exception table and all of that.

Now, on to write a test program and make it say hello over serial! ​

There are so many wires in this thing, I can hold it up like a pizza slice without it bending. ​

#retrocomputing #m68k

Show threadMr LeastAug 8, 2023
@thankfulmachine That's beautiful! Is that two dual UART chips?
Show threadThankful MachineAug 8, 2023
@luskebux Thank you! Yes, two 68681 compatible DUARTS there. I intend to dedicate one for debugging and at least one for inputs. Probably the last will be for The Old Net modem or something :)
Show threadGlaireDaggersAug 8, 2023
@thankfulmachine Nice!!
Show threadThankful MachineAug 8, 2023
@glairedaggers tyty!
Show threadW4IPAAug 8, 2023
@thankfulmachine I have been wanting to do something like this with a 6502. I actually started it but got really tired of cutting all the custom length wires lol
Show threadThankful MachineAug 8, 2023
@W4IPA I feel that. Normally I wouldn’t have the patience but something about it gets me into the right frame of mind
Show threadAlanna 🏳️‍🌈🏳️‍⚧️Aug 8, 2023
@thankfulmachine nice work! This is inspiring, thank you for sharing. My own efforts at 68k breadboarding have not been as successful.
Show threadkyleAug 8, 2023
@thankfulmachine Nice! I like the little twisted pair for the clock.
Show threadAlexander KnochelAug 8, 2023
@thankfulmachine Amazing, after my misadventures with RF experiments, I wouldn't have expected those breadboards to reliably work at 8 MHz digital
Show threadColin HaynesAug 8, 2023
@thankfulmachine Nice work. Nice scope too. I've been bumbling along with a cheap USB Hantek scope while fixing my Commodore PETs - what's your scope please?
Show threadArxAug 8, 2023
@thankfulmachine Ohh, I really want to make my own breadboard computer. 65C02, 32kb RAM, 32kb ROM, VIA, keyboard and a simple video display generator. Wish I knew how, though. 😹
Show threadiPostHumanAug 8, 2023
@thankfulmachine Cool! I have a 68008 and have thought about breadboarding it. You wouldn't happen to have schematics available? 😀
Show threadEthan BlantonAug 8, 2023

@thankfulmachine A beautiful job!

Where do you get your breadboards? I have a bodged-up TMS 9900 build that boots, but when I tried to clean it up onto new breadboards, I'm having a lot of trouble because too many of them have contact resistance that's too high and I'm getting nightmarish ground bounce.

Show threadThankful MachineAug 8, 2023

@elb Thanks! I get my bbs from http://www.busboard.com. I use the BB830

It might be interesting to measure the two with equivalent simple circuits so you can see what is going on. There are often many things that you can do to minimize your signal integrity problems!

Home | BusBoard Prototype Systems

Show threadEthan BlantonAug 8, 2023
@thankfulmachine Thank for the information, busboards are my next stop. They're pricey, but seem to be consistently well-liked. I have seen some complaints about their post-COVID-shortages boards (I believe, e.g., on the EEVblog forum), but I'm hoping those have been resolved now that there are fewer material and logistic shortages in general.
Show threadThankful MachineAug 8, 2023

@elb Yes, I think they should be available. Give them a go, I like them quite well, I think they are worth it.

They also sell on Amazon if that is useful to you. Cheers

BB830 Solderless Plug-in BreadBoard, 830 tie-Points, 4 Power Rails, 6.5 x 2.2 x 0.3in (165 x 55 x 9mm) https://a.co/d/7uGNCko

Amazon.com

Show threadMUSE Bi-VisionAug 8, 2023
@thankfulmachine the sheer amount of ringing on /AS is sending me, totally understandable why it's happening, but it looks great on the scope. nicely done
Show threadThankful MachineAug 8, 2023
@nkizz Thanks. It’s the crummy probe (and my probing cleanliness, I was excited after all)
Show threadzwangseinweisungAug 8, 2023
@thankfulmachine now, have a look at #EmuTOS You have to do it 😁
Show threadIan MoltonAug 9, 2023
@thankfulmachine Those waveforms look nicer than some I've seen from machines built on a PCB...
Show threadAndreas (82mhz)Aug 15, 2023
@thankfulmachine That looks amazing! I'm impressed and slightly jealous ;)
Show threadThankful MachineAug 16, 2023
@82mhz Shucks. Thank you!
Show threadPaula MaddoxAug 17, 2023
@thankfulmachine nice work!
And such a tidy breadboard.
Show threadChewieMar 2
@thankfulmachine Impressive cable routing!