Usually, on classic VDP, you may easily update the SPAT during VBLANK, as there is only 32 entries.
With the V9990, you have 125 entries, which make for a longer update (I came up with a code taking 12600 cycles).
Is there another technique ?
Maybe splitting the update between 2 frames ?
Well, obviously you have to update 125 entries (don't know if each one has 4 like classic VDP or more bytes) only if you use 125 sprites... if you don't need such big quantity you can update less...
Write 500 bytes take a significant amont of time on the CPU side. Nothing problematic for a tech demo but still big for a real game. But the real problem is on the gameplay side: updating 125 entities can take a huge amont of time depending on the gameplay needs. For example, don't expect to throw 100 bullets and to be able to check collision on them each frame.
