GFX9000 question

By Huey

Prophet (2694)

Аватар пользователя Huey

29-06-2011, 16:10

I have some questions about handling the P1 mode of GFX9000 for games:

1. The gfx9000 does not generate an interrupt signal to handle in an ISR (IM2???) . Do I need to test the interrupt on the gfx9000 myself?
2. How big is the VBLANK period (kb's)? I want to update the pnt(s) and sat in that period to avoid page tearing. (update is done writing the pnt/sat from RAM to VRAM)

I am just in a planning phase. I have no real gfx9000 to test.
Thanks in advance.Running Naked in a Field of Flowers

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By anonymous

incognito ergo sum (116)

Аватар пользователя anonymous

29-06-2011, 17:10

The assumption in your first question is incorrect.
The answers you seek can be found on MSX Banzai!'s Gfx9000 page in the development section.

By Huey

Prophet (2694)

Аватар пользователя Huey

29-06-2011, 17:14

Thanks G.
I have already read it. Thanks for the RTFM Wink

R#9 -> IEV = 1

So the interrupt from the gfx9000 will cause an RST38h (IM1).
So I just have to enable the interrupt and disable the MSX vdp interrupt... This helps a lot.

Still. My knowledge it too limited to figure out the amount of bytes I can process in VBLANK.

By Huey

Prophet (2694)

Аватар пользователя Huey

29-06-2011, 19:09

update: KB's in VBLANK will be somewhere around 1KB.

By Edwin

Paragon (1182)

Аватар пользователя Edwin

29-06-2011, 22:07

The interrupt will cause whatever IM is set to. Also note you can turn on line interrupts and CE completion interrupts as well on v9990.

As for upload speed, this is cpu limited and therefore the same as for v9938. On z80 anyway. Which at best is somewhat over 768 bytes in 60 Hz mode. So considering the size of two P1 nametables, I'd suggest another approach. Tongue