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+
+classic digitalWrite() gives ~500ns pulse time (2MHz)
+
+gpio_write_bit() is about 360ns (2.78MHz)
+
+writing to GPIO?_BASE is about 60ns (16.6MHz -> 18MHz)
+
+pwm write 0x0001 is about 30ns (33MHz)
+pwm write 0x0001 is about 14ns (72MHz) with prescaler as 0 (!)
+
+1/25.125MHz = 39.72ns
+
+crude 640x480 directions:
+ www.epanorama.net/documents/pc/vga_timing.html
+ 480 lines
+ 31.77 us horizontal line length -> 2287.44 clock cycles -> 2287
+ 3.77 us sync period -> 271 clocks -> 271
+ 1.89 us front porch? -> 136 clocks -> 136
+ 25.17 us video -> 1812.24 clocks -> 1812
+
+ so...
+ 2287 reload
+ 271 1: Hsync high
+ 407 2: Video on
+ 2219 3: Video off
+ 2287 4: Hsync low
+
+ vertically, it's
+ 480 lines active video
+ 11 lines front porch
+ 2 lines Vsync (low)
+ 31 lines back porch