More graphics tiles

[Under4Mhz]

The original models of the Microbee only had 2K (128 tiles). I've read later models had more tiles than video space. Which models had more memory? How common are these models? If I were to support these models only, would it be worthwhile, or would I not be able reach many users?

Alternatively, is it possible to put the Microbee into a 32 column mode? That way, the number of tiles available are effectively doubled (since the screen can be filled with less).

[MbeeTech]

G'day Under4Mhz

The Microbee Premium series & 256TC has the extra PCG memory.
Normally these machines were supplied with 8 banks of PCG memory which was enough
to have a full 64 x 16 character screen (resolution 512 x 256) without running out of
PCG characters. The Premium series machines are reasonably common but there are still
more of the 'Standard' (Non-Premium) machines out there. The 256TC is pretty rare
as they didn't sell particularly well.

The Premium & 256TC also has the 'Viatel' option fitted as standard which would allow
32 / 40 column mode. This option halves the video dot clock rate so that 80 columns
becomes 40 columns.

Have a look at the Microbee Technical Manual in the repository for details on how to access
the extra PCG banks in the Premium series.

[someone]

...is it possible to put the Microbee into a 32 column mode? That way, the number of tiles available are effectively doubled (since the screen can be filled with less).

This is what someone often does. Have a look at the doppelganger posts on this forum for some examples.
It's very important to use 40 column mode for a 32 column display otherwise the keyboard scanning on the alpha and alpha plus models will be incomplete.