display: during the prefetch interval, run at full speed

We have one character worth of prefetch, but that is one character
at full speed (80 columns).  So advance the counter at full speed
during the prefetch interval.  The alternative would be to adjust
the timing of the prefetch start dynamically (otherwise the text would
move between 40 and 80 column mode), but that seems to be more
complicated especially when using the FG unit.

1 files changed, 3 insertions, 1 deletions

diff --git a/display.v b/display.v
index 2b7e8f3..3360138 100644
--- a/display.v
+++ b/display.v
@@ -128,7 +128,9 @@ module display (
    wire 	 do_hide = wasdble ? washide : ishide;
 
    // Should we advance the character pixel?
-   wire 	 advance = width | x[0];
+   // We need to always advance at full speed during prefetch, or
+   // we would have to start the prefetch earlier in 40-character mode.
+   wire 	 advance = width | x[0] | prefetch;
    
    // Address mapping for 40 and 80 characters
    assign 	 a80[3:0] = xchr[3:0];