RETRO Innovations

With the introduction of the TANDY Color Computer (CoCo) 3, engineers were faced with 2 significant and implied mutually exclusive goals: Design a worthwhile successor to the venerable CoCo 1 and 2, enhancing the capabilities of the machine in non trivial…

As noted in a previous post, along with finding that Green Mountain Micro (GMM) had created a lowercase modification for the CoCo called “lowerkit”, Eurohard SA also created a lowercase update for the Dragon 200e for the Spanish market, which I think was…

Another Player Enters the Game While searching for TANDY Color Computer external font solutions, I found information on a similar solution that was created for the Dragon 200e.

Having found some external fonts used with a MC6847 lowercase modification from “back in the day” (the lowerkit product from Green Mountain Micro) and converting them into ROM-burnable images, I determined a ROM font was composed of 12 bytes of font bitmap

Searching for Information As I was trying to decipher how to leverage an external character font ROM with the MC6847, I searched for existing project/products in this space.

Understanding external character ROM functionality on the Motorola MC6847 Video Display Generator (VDG) I’ll be honest, I rarely use lowercase characters on any of the classic computers I use.

Addressing the Color Computer 3 DMA operation challenges via hardware modification, while pretty simple, limits initial adoption.

Radio Shack’s introduction of the Color Computer 3 introduced extensive changes to the Color Computer design.

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.

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.