[Coco] CoCo BASICS - clarification on the differences?

[Mathieu Bouchard]

Nope, ECB1 takes 16k of ROM, that is, 8k of ROM for CB itself which is the main 
programme, and then a 8k of ROM that is a plugin for CB that turns it into ECB1.

Shadow RAM is when you use RAM to hold a copy of ROM, which makes them 
modifiable using POKE (same feature exists also on the PC, on which the RAM was 
also faster than ROM, but on the Coco you don't have that speedup). For Cocos 
that have less than 64k, this feature is disabled and irrelevant.

The reason ECB1 would "require at least 16k" is because 4k is too tight when 
using graphic modes (PMODE). CB's own reserved RAM always takes the first k of 
RAM, then 32x16 text/semigraphic mode takes the next half k, and then you have 
2.5k left for your tokenised BASIC program, plus all your strings (A$,...) and 
arrays, plus the graphics mode RAM (which can't overlap the text mode RAM). 
PMODE 0 takes 1.5k per screen ; the other PMODEs take either 3k or 6k per 
screen.

Technically, there is enough room for using ECB1 or ECB2 with 4k as long as no 
graphics are used, or if only PMODE 0 is used and the BASIC programme is very 
tiny, but it doesn't mean that the authors bothered to make ECB able to run with 
4k of RAM, I don't know.


Le 2017-04-04 à 10:35:00, Steve Strowbridge a écrit :

> I think you got all the answers, but here's what I think I know/remember.
> The first CoCo had two options, Color BASIC and Extended Color BASIC.
> Color BASIC would run with as little as 4K, but Extended Color BASIC
> required 16K of RAM because I think the ROM itself was 8K

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| Mathieu BOUCHARD --- tél: 514.623.3801, 514.383.3801 --- Montréal, QC