History & Philosophy

In the early 90's several attempts at a CoCo 4 were made the MM/1 and the Tomcat being among the most notable no more then a few hundred ever sold they had many good points but also many issues when it came to backwards compatibility with the CoCo 3 and eventually in the 2000's with FPGA becoming more powerful a second wave of "CoCo 4 's " appeared I'm talking about you MISTER MATCHBOX but many of the same problems continued.

Around 1994 I had a concept of how a CoCo4 should be I think it was partly inspired by the idea of having multiple TC9's in a Tomcat and later by Sock Masters idea

see: http://www.6809.org.uk/twilight/sock/cocofile/coco4.html


The main problems I had with many of these designs was lack of comparability and lack of a Cartridge Slot I also felt that I liked the computer in a keyboard design of the CoCo3 while wishing that more expand ability was possible without resorting to that Big Ugly Monstrosity canned the Multipack.

My general Idea consisted three 6309's packaged such that two could act separately as two independent coco's or together to be more powerfully with independent but synchronized clocks that could run at coco2, coco3, 2x  or  4x rate up to 7.152 MHz.  These CPU's would have a cooling fan above them and a third 6309 cpu would focus on controlling the hardware allocation.
This hardware would consist of all the same ports that the coco 3 had except for RF out which would be droped most of these would be enhanced the joysticks would be 8 bit rather then 6 bit the Bit Banger would have a few extra control lines to use with a special cable but be able to use standard coco bit banger cables as well. The Cassette tape port would be improved and have a 3000 baud or maybe even 6000 baud mode and the ability to be used as an audio digitizer. The Composite out would be the same RCA port but the quality of the signal would be better the audio out RCA port would be replaced with a Stereo Jack and the RGB port would remain unchanged.

The missing RF Modulator would be replaced with VGA out and other changes would include Dual Midi Ports and the Internal Power Supply would be replaced by a Molex connector so that standard PC  hard disk power adapters would work as external power supplys.

The system would come with 4M of RAM and include a 160K Battery Backed RAM disk and a 8K Battery Backed Keyboard Macro Memory using three C batteries for when the system not plugged into AC. And an 8K Settings Memory powered of a long life button battery,

The Graphics capabilities would  include at least 512 native colors and the ability to flicker quickly between two screens. Color Screens would be capable of at least 450x720 and a monochrome  or grey scale screen would be capable of displaying 60 rows of a 132 column wide screen at 1056x720 or at least 924x720 resolution.

The Concept in Block Diagram format would be:


The memory layout would be like this:


Mother board layout something like this:


In any case this idea changed over the years,

As it seemed unlikely that anyone would attempt a Multiple CPU coco anytime soon my Coco 4 ideas got scaled back and the original coco 4 concept renamed CoCo5.

As time went on I came up with some philosophy for how an advanced coco should work.


Well that's about all I can think about now.