A CRTC programming technique used to split the screen into more than one block vertically.
The sizes of each block are defined using CRTC register R4. Vsync is turned off in all but one block (by setting CRTC R7 to a value larger than R4).The start address of each block can be changed using CRTC registers R12 and R13. This allows each block to reference different ram, or to hardware scroll one block while another is static. This list method requires careful timing for the CRTC register updates, it also needs testing on all CRTC because there are differences of when each will accept and use the values programmed. However, the result can be made to work on all with more simple ruptures. Care must also be taken to ensure the timings are setup for a 50Hz screen. It is worth noting that some monitors are more tolerant to longer or shorter frames so the result may appear correctly on them and not exhaustiveon others.In addition some games may have been programmed and tested on only 1 CRTC type so may not work on others. This is a an incomplete list of games that use this technique:
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