#549 Limit V99x8 VDP VRAM access in MSX1 modes

Next_release
closed-fixed
None
5
2014-09-14
2014-08-02
No

Currently, the limits on accessing the VRAM in the V99x8’s MSX1 modes are not emulated.

As I understand it this information is available from the openMSX team’s V9938 measurements, just not interpreted and implemented yet.

Discussion

  • Laurens Holst

    Laurens Holst - 2014-08-02

    <wouterv> kanima, grauw: (very preliminary results) i started looking at some (old) logic-analyzer measurements we took on a v9938, more specifically for the msx1 modes (i mostly ignores those for my VDP VRAM timing article) ..
    <wouterv> .. it seems that on v9938 both text1 and text2 follow exactly the same vram access pattern
    <wouterv> so text1 is doing the same number of vram reads as text2, but more than half of them are dummy reads
    <wouterv> similarly all character modes use the exact same access pattern. So even though multi-color mode (screen 3) doesn't really need a color table, it still fetches dummy data at those moments in time

     
    Last edit: Laurens Holst 2014-08-02
  • Manuel Bilderbeek

    • status: open --> closed-fixed
    • assigned_to: Wouter Vermaelen
     
  • Manuel Bilderbeek

    Implemented in commit 7f52e8691b340a1f85de5805113cfd5f33ee0772 by Wouter. Thanks!

     

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