3rd time's the charm..?

A project log for AWP68k

Following the grand tradition of 68k homebrew. It's an exercise in integration, writing device drivers, and eventually something like an OS

RELREL 09/27/2021 at 06:020 Comments

The newest boards showed up! 

The assembly was a giant pain (as always) but the design seems solid. So far I've taken the DUART, PIT, RTC, ROM, RAM, and PS/2  chips through their paces. No stability problems or unexpected errors yet while cruising along at 10Mhz, and with a little care 12Mhz is conceivable. I'll throw it on the scope and see just how ugly things are under the hood though. Still haven't bothered with the FDD and HDD yet but I'm not overly worried about the interfacing - more with writing drivers/software.

There's the good news. The bad? 

The DMA chip has been temporarily pulled. It was causing funny business. *Really* confusing funny business. Analog, intermittent, signals-in-places-they-ain't-attached-to kinda funny business. Considering the layout and configuration are totally unambiguous and copied directly from the datasheet, it's even more frustrating, and I'll have to find a day with a few solid free hours to start scoping things out and hunting the cause down. I almost wanna jump the gun and blame it on component failure/manufacturing errors, but that's still wishful thinking at this point. I just know that the board is clean, the joints look great under a microscope, and a chip is causing an error on a net it isn't attached to. sigh..

On the software side I've built a nice toolchain, and ported a handful of monitors/bootloaders. I even have the rosco68k firmware up and running, so that should increase the code base to play around with substantially. I still have to decide just how hard I want to lean into OS development. For now I'm happy with a little single user single process bare-bones BIOS, but who knows how that will change..