dim msx basic
I've got this idea, and I don't know whether it makes sense or whether it works. Perhaps soms system guru like NYYRIKKI would know. BASIC is partly slow because of error checking. If you write outside the bounds of an array, you get an error. This error is actually pure luxery, because normally the system would just behave strangly, or may even crash (if you'd overwrite code with data).
Would it be possible to
1) read out (dmp) the BASIC ROM
2) erase all the error checks
3) load the adjusted BASIC into RAM and use it as such
?
See it as a kind of 'release mode', when you replace the foolproof yet slow BASIC with a faster yet crash-prone altered BASIC. You'd still develop your game in standard BASIC, and once it's all finished, you run it in the adjusted BASIC.
Or, is this a bad idea? 
@Vampier: Okay, I am not familiar with pokes. Which addresses area available to store 256 values 