Started digging into the broken BBC Master 128 I have. Previously I’d replaced a failed Video ULA, which at least got the right clock signals in the right places. This time around I observed that the /IRQ input pin was stuck low on the CPU - ie, an interrupt was being generated. That signal appears on the 6850 (IC45 pin 7), the user 6522 VIA (IC6 pin21), the system 6522 VIA (IC8 pin 21), and the custom memory controller IC (IC20 pin 29)....
The new NTSC VIC arrived - let’s see if it fixes the issue, or I’ve made an expensive mistake!
A quick update on where the Vic-20 repair is up to.
In this video I take a look at a Vic-20 I brought back from the USA on a recent trip.
Well, that was disapointing! Growing tired of Windows and Microsoft’s shenannigans I figured I’d install Linux on another one of my machines. I do all sorts of things on this particular machine, and one of those things is that I sometimes edit videos with Davinci Resolve. Most of my video editing is done on a much beefier machine downstairs, but the projects are kept in a Postgres database and the media on a NAS, so I can edit from any machine on the network....
Recently I built up a little Raspberry Pi 4B to use while I travel. I use it for: Travel router: Built in wifi for my laptop and phone to connect to; An external USB WiFi dongle for connection to Hotel WiFi; A USB ethernet to connect to Hotel internet if wired is available; The built in ethernet for connecting to network equipment I’m working with; A 4 port USB serial adapter to provide serial console access into equipment; This lets me use my laptop with Hotel internet without exposing my laptop directly to it :-) It also lets me talk to network equipment, either via ethernet or serial over WiFi....
This time we’re constructing the PiDP 11.
This one is a bit different. My Dad dropped this by and asked if I could work out what it was. Being new year time, I was still in bed and missed talking to him so I had no background information to work with.
In this video I’m preparing the Raspberry Pi for the PiDP11 project. I’m doing this up-front so I can use it to test the hardware build during construction.
In this video I take a look at the Acorn Electron, and more specifically the ULA. It’s the heart of the system and creates one major difference from the BBC machines the Electron is derived from. A few references: Stardot - https://stardot.org.uk ULA schematic thread - Electron ULA Schematics - stardot.org.uk FPGA ULA project - Electron FPGA - stardot.org.uk