CoCo DMA: All Charged Up!

April 4, 2020 RETRO Innovations

Addressing the Color Computer 3 DMA operation challenges via hardware modification, while pretty simple, limits initial adoption. It places the technique into a classic “chicken and egg” situation. The CoCo3 provides an ideal platform for DMA capabilities, but owners will only perform hardware modification if highly desired peripheral capability demands …


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 …


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 …


RAM Expansion for the C64

May 22, 2018 RETRO Innovations

RAM expansion was a common topic in the Commodore 64 community in the 1980’s.  Everyone seemed to need or want more RAM:

Soon after the unit arrived in stores, Paul Bosacki published a way to upgrade the unit to 512kB Later, he pushed the expansion to 1MB Berkeley Softworks (later …



May 7, 2017 RETRO Innovations

Glenn Holmer captured me talking to friends about something of interest at the ECCC 2014 show

It’s interesting to be a part of the continuing “growth” of the classic computer scene.  And, perhaps it is just me, but it does appear the classic machines are seeing more interest now than


Back from the Vintage Computer Festival – East 9.1!

April 11, 2014 RETRO Innovations

I just returned from a 2102 mile roundtrip excursion to the Vintage Computer Festival – East 9.1 at InfoAge in Wall Township, NJ.  Having been prevented from holding the show in 2013, the VCF-E organizers went all out for the 2014 show, supporting 2 exhibit halls and a separate speaker

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Heading to the Vintage Computer Festival East!

March 30, 2014 RETRO Innovations

The ninth “annualish” Vintage Computer Festival East will be held April 4-6, 2014, at the InfoAge Science Center, in Wall, New Jersey.

VCF East is a celebration of computer history from the 1940s-1980s. The schedule includes a hands-on exhibit hall, technical workshops, lectures, a marketplace, tours of the InfoAge museum