CoCo DMA: Missing Without a Trace

March 23, 2020 RETRO Innovations

Radio Shack’s introduction of the Color Computer 3 introduced extensive changes to the Color Computer design. Gone were the 6847 VDG and 6883 SAM, functionally replaced and enhanced with the TCC1014 Advanced Color Video Chip (ACVC) which most folks reference as the GIME. Other additions included an additional 64kB of …


CoCo DMA: Invisible RAM

March 12, 2020 RETRO Innovations

Now that we’ve learned a bit about how the 6809E wants to be treated during a direct memory access (DMA) request, we can put all we’ve learned into action. But, before we launch into the details, let’s address some questions that arose during previous article discussions: Some asked why the …


CoCo DMA: “Fighting on the bus”

March 5, 2020 RETRO Innovations

Picking up from last time, we were able to successfully place a byte into the internal CoCo memory from the cartridge port without the use of the CPU by utilizing a direct memory transfer procedure. However, after the transfer, BASIC programs would stop with errors at times, machine language programs …

Apple II

UJOY/1A – USB interface for Atari Joysticks

February 28, 2020 GGLABS

Project Status: releasedReal Atari 2600 Joysticks are necessary for a truly authentic feel when using an emulator. The UJOY interface allows to connect one Atari Joystick to a standard USB port. The Atari joystick is a very simple device. Just 5 switches directly connected to a female DB9 connector. We used …


CoCo DMA Early Efforts

February 28, 2020 RETRO Innovations

As referenced in, I am attempting to coax some direct memory access functionality from a TANDY Color Computer. I’ll be utilizing a TANDY Color Computer 1 for initial testing, as I feel it most closely matches the Motorola 6809 reference architecture and this year is the 40th anniversary of …


Direct Memory Access Possibilities on the TANDY Color Computer

February 26, 2020 RETRO Innovations

As part of my continuing efforts to understand direct memory access (DMA) capabilities of various 80’s home computer systems, I decided I should figure out what, if any, DMA capabilities are possible on the TANDY Color Computer systems. There are 3 essential models in the lineup, though from a technical …

Apple II

New Store Item – Apple II Plus, Rev 7 RFI Motherboard

February 15, 2020 ReActiveMicro

We’re glad to announce a new item in the ReActiveMicro Store: The Apple II Plus, Rev 7 RFI Motherboard The Apple II Plus, Rev 7 RFI Motherboard project is offered in several options. As assembled or kit, with and without ICs and DRAM, and in 93-series ROM (original) or …

Apple II

New Store Item: No-Slot Clock

January 11, 2020 ReActiveMicro

We’re glad to announce a new item in the ReActiveMicro Store: The ReActiveMicro No-Slot Clock v1.0 The No-Slot Clock fits in all Apple IIe, IIc, and clone systems with 28 Pin ROMs. Comes standard with two CR1025 cells installed, which offer about 1 year of standby time to keep …