Since I obviously haven't been programming on the BBC for very long, and don't yet have a BBC, this may be a stupid question.

Is it normal that you have to get things working both with and without the Tube? I've never really seen one in action, so I'm not all together sure how easy it is to remove (if you can just unplug it, or if it's wired inside the BBC, etc). I mean, are most games compatible with BBCs with and without the tube?


If tube compatibility is normal, what is the best way to clear the screen in mode 4?

A lot of games do not work with the TUBE. Some games, e.g. Elite, had a specially written version to work with the TUBE. Writing a game to be TUBE compatible would be a lot more hassle than it is worth to be honest.

If it is an external TUBE co-processor then it is simply a case of switching it off. If it is an internal one you can do a '*CONFIGURE NOTUBE' to disable it on a Master.

I wrote some example code for detecting whether or not the tube was in use (see 'Sample Code' section) if you want to either notify the user to turn off the TUBE or use TUBE specific code.

Kind regards,

Francis

Ah, OK, thanks

I found that pretty much the whole game is tube-incompatible, since it writes directly to screen locations (I believe that is what makes it incompatible), so yeah, it would be too much hassle.

You'll find most games are unworkable on the Tube - you need to write directly to the screen to get any speed at all on the Beeb, which can only be done from the main processor.

Properly-written games /are/ compatible with the tube, you just make sure your load and execution addresses are in the I/O processor.

...Wow, revelation. When utilities like the GoMMC tools make you turn it off, I'd always assumed...