It's possible to use 32KB screen size (used for [[Programming:Overscan|overscan]]) by setting bits 11 and 10 of Register 12 both to 1. Bits MA11 and MA10 of the address generated by the CRTC are not written on the address bus to access video memory; settings both bits to 1 is the only way to cause a carry to bit MA12 when address pass over the end of current video page to change the memory address to the next video page.
.{| class="wikitable"|------- REG ! colspan="8" | Register 12 --------. .------- REG ! colspan="8" | Register 13 --------. | | | |- ! 15 !! 14 !! 13 !! 12 !! 11 !! 10 09 08 07 06 05 04 03 02 01 00!! 9 !! 8! 7 !! 6 !! 5 !! 4 !! 3 !! 2 !! 1 !! 0 .|--.--.--.--.--.--.--.--. .--.--.--.--.--.--.--.--. |X |X | | | | | | | | | | | | | | | colspan="2" |Unused '--'--'--'--'--'--'--'--' '--'--'--'--'--'--'--'--' '--.--'--.--'---------------.-----------------' | | colspan="2" |Video Page | colspan="2" | '------> Offset for setting videoramPage Size | colspan="10" | Start Address (1024 positions) Bits 0..9 | | | '-------------------------> Video Buffer | '-------------------------------> Video Page}
{| style="white-space: nowrap;"
|
{| class="wikitable" style="margin-right: 32px"
|+ Video Page
|-
! Bit 13 !! Bit 12 !! Video Page
|-
| 0 || 0 || 0000 - 3FFF
|
{| class="wikitable"
|+ Page Size
|-
! Bit 11 !! Bit 10 !! Page Size
|-
| 0 || 0 || 16KB