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Old 23 February 2014, 14:59   #9
Toni Wilen
WinUAE developer
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,542
Originally Posted by mark_k View Post
How is the displayable area determined for programmed modes? I checked various ECS modes (the monitor drivers use slightly different settings on AGA machines, maybe something related to fetch mode?).

It seems that HTOTAL + 1 - (HBSTOP - HBSTART) gives the number of displayable colour clocks (so multiply that by 8 to get number of 35ns pixels). At least for all modes I checked except EURO36.
It isn't that simple. It only tells maximum possible visible area.

Display can't start very early and DDFSTRT/DDFSTOP and DIWSTRT/DIWSTOP also needs to fit perfectly inside "blanking viewport" or part of display will be clipped.

For example in many modes hblank ends before bitplane fetches start (hblank end < DDFSTRT), part of left edge is filled with border color.

EDIT: updated, does IDE messages still appear? (I assume this was introduced in b9?)

Last edited by Toni Wilen; 23 February 2014 at 15:12.
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