5 Jul
2012
5 Jul
'12
11:53 a.m.
Alexey Toptygin wrote:
The Spectrum isn't really bitmapped. IIRC you
define up to 20? 8x8 pixel
tiles (one bit per pixel) and can draw them in place of characters (i.e.
at any multiple-of-8 pixel vertical or horizontal offset from 0) with the
same color and bright/flash attributes as normal characters. That was the
case in BASIC, at least, maybe you could do more in assembly, but I don't
recall seeing a frame buffer in the memory map...
When the Spectrum came out, I had the impression that it was a text mode
machine with redefinable characters like many of its competitors. Given
that this was a popular hack to give the ZX81 "high resolution" graphics
and the way color is controlled in 8x8 pixel blocks, this was a
reasonable guess. But I learned otherwise a few years ago.
The only hardware mode is a simple 256x192 bitmap starting at 0x4000
which is modified by a 32x24 attribute map at 0x5800. The model
presented by Basic is what you described, but the model seen by assembly
language programs is very similar to what the Mac had.
-- Jecel