On Wed, 1 May 2002, Robert Newson wrote:
> Al Feng wrote:
>
> > Essentially, when you swap QL ROMs, the video output for "TV" mode
> > changes from NTSC to PAL and vice-versa for JSU & JS, respectively.
> >
>
> Errm...don't the ROMs contain the CPU instructions...the video output is
> shurely the job of other board chips (ZX8301, etc).
>
> However, (these are speculation/vague memories [of rumours?]) the screen
> shape is different(?) and so the drawing routines would be modified (so a
> CIRCLE is still a circle). Also, would the interrupt routine be running at
> 60Hz as opposed to 50Hz, and so some timing routines would have been rewritten?
I suspect you're both right and both wrong. A US QL with US timings would
have problems drawing a UK-resolution screen in the reduced time - I
imagine the machine would slow down greatly. Similarly, I suspect a UK QL
with US ROMs would speed up slightly. (Slower scan rate AND less to scan)
The question is based one xperimenting I'm doing with my US QL. Nasta may
want to jump in, but I am also wondering what kind of headroom the
original QL mobos have for 'overclocking', in the sense of maybe adding a
faster clocked 68008FN at 10-12MHz. I think the on-board RAM would
definitely fail at those speds and may have to be removed/neutered ;)
Finally, I'm thinking of putting up a web-based survey form asking what
systems people use, so I can get an idea of the proportions of different
system types out there. The results would help traders aim products at the
right group of people (ok, at the expense of the hapless minority still
using their original QLs with SPEM memory and DiRen kbd interfaces, who do
all their programming in Forth ;)
Dave
http://ql.spodmail.com/
