John Linville
Blogs

Software Sprite

January 14, 2023 John Linville

As often discussed, the Motorola 6847 VDG offers little in terms of assistance for game programmers or other software authors. While many contemporary video chips offered assistance in scrolling backgrounds or in moving objects in the foreground of a display, the 6847 hardware merely provides access to a static framebuffer. …

John Linville
Blogs

Scrolling Engine

January 10, 2023 John Linville

Well, it’s been a while!  Despite the boredom and isolation that came along with the COVID years, I didn’t do much that was very impressive in terms of retro programming during that time. In a cruel twist of fate, the boredom (and an ongoing spat with another CoCo media figure) …

John Linville
Blogs

Recovering VTL-09

July 10, 2022 John Linville

 A few months ago, a retrocomputing post from David Wiens caught my attention. The post indicated that David was looking for some assistance in recovering an old piece of 6809 assembly language software that he had keyed-in from a listing in a book. The software in question was a 6809 …

John Linville
Tandy

CoCo joystick tester prototype

January 15, 2022 John Linville

Some simple testing/verification of a tester for the Tandy Color Computer and Tandy 1000 joysticks. LEDs are used for bar graphs that approximate the X and Y axes, and to indicate button presses. I plan to respin the PCB to use a PCB-mounted DIN connector and to cleanup a silkscreen …

No Picture
Blogs

Timing & Cycle Budget

January 25, 2012 John Linville

I am still dragging a bit after my weekend road trip.  Plus, my days off from work have left me playing a lot of catch-up.  So, I haven’t had much time this week for progress on Fahrfall.  Fortunately, I still have some background topics I would like to cover! 🙂 …