[Coco] Coco4 thoughts

[jdaggett at gate.net]

On 2 Jan 2009 at 17:27, Frank Swygert wrote:

> 4. Video. Must be CC3 compatible, and I'd really like to see video on
> board. If on board it must be compatible with off the shelf monitors.
> If the new machine's main purpose is for experimenters/learning
> basics, however, it could rely just on a TV for a monitor. I don't
> like the idea of having to rely on a PC, but in reality it could be a
> hardware board that could work alone, but require a PC for video and
> programming input. Most would really like to see higher resolution --
> at least 640x480. 640x192 is the highest the CC3 will produce. More
> than 640x480 would probably take costs way up due to memory and
> hardware requirements.

Frank

640x480 in itself is not that expensive an overhead. In fact 8Megs of 
SDRAM is as cheap if not cheaper than 512K of Static RAM. So doing 
640x480 in 256 colors is not a real cost increase. More an issue is which 
block of 512k to use. 640x480 256 colors will require 307.2Kbytes of 
memory. That more than fits in the base 512K CC3. In a 2M CC3 we have 
four such 512K blocks. That then could allow a desktop of 800x600 256 
colors. 480Kbytes. Inside the FPGA this is easy to do. The harder part 
maybe in adapting the OS to recognize this enhancement. 

Still a dedicated CC4 PCB is going to be in the range of $8-$12 a square 
inch. Much will depend on how many are produced. Better of is to optain an 
FPGA development board with enough expansion to add a dedicated I/O 
card. One in mind is the Digilent Inc Nexsys2 board. At $99, it has a 
Spartan 3E 500K that is more than large enough to do a CC4. for $20 more 
one can expand up to a 1200K gate FPGA. An I/O card then could run in 
the $40 to $70 range and still meet the $200 criteria. 

james