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Beginners > Sending 2 bytes at a time to video mem

#66574 - pure_ev1l - Thu Jan 12, 2006 2:08 am

is it really nessesary to send 2 bytes at a time?

I only ask because I havent got a cart yet (next week) so I am playing around with emulating it, I'm guessing the visual boy advance is just more tolerant right?

if I write 1 byte at a time to video memory on actual hardware will it do the thing ppl have mentioned (upper and lower byte same). as I have a small problem with writting 2 bytes....

I'm making an dynamic loading tile game, and I need it to load 1 row of tiles down the left and right edges of the screen (of screen)

as the screen is 30 tiles wide, and I have set buffer to 32x32 tiles, what should I do? (if I need to do anything about it)

hopefully I dont need to make a change, as it works perfectly on visual boy advance, but I suspect that is just VBA not being true to the hardware?
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#66580 - kusma - Thu Jan 12, 2006 2:31 am

visualboy advance emulates the problem correctly. both bytes are set to the same value. sure you aren't just not noticing that the x-resolution is divided by two? remember, you're only getting every second pixel drawn twice. kinda like a shitty mosaic-effect.

#66607 - pure_ev1l - Thu Jan 12, 2006 12:18 pm

I'm writting the tiles and palette 2 bytes at a time.

so no, I'm not getting 2 pixels at a time the same.

I'm writting 2 tiles at a time... is that ok?
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#66613 - wintermute - Thu Jan 12, 2006 1:46 pm

map entries are two bytes, unless you're using rot scale mode

#66645 - thegamefreak0134 - Thu Jan 12, 2006 5:52 pm

I'm sure that if this looks right on VBA, it will on hardware too. VBA is generally weaker with things like sprite and window clipping and has minor timer issues, but this kind of thing is true I believe.
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#66646 - pure_ev1l - Thu Jan 12, 2006 6:00 pm

cool, thanx guys :-)
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#66656 - Ultima2876 - Thu Jan 12, 2006 6:48 pm

What kind of timer issues?

#66658 - poslundc - Thu Jan 12, 2006 7:02 pm

Ultima2876 wrote:
What kind of timer issues?


Unless they've fixed it in more recent versions, in my experience it did not correctly emulate the waitstates for the different areas of memory.

As a result, my initial Mode 7 engine looked fine in VBA but would overrun HBlank on hardware.

Dan.

#66737 - tepples - Fri Jan 13, 2006 6:46 am

poslundc wrote:
Unless they've fixed it in more recent versions, in my experience it did not correctly emulate the waitstates for the different areas of memory.

On those versions, just about any code ran faster on VBA than on hardware, but DMA copies took about the right amount of time.

Quote:
As a result, my initial Mode 7 engine looked fine in VBA but would overrun HBlank on hardware.

Recent versions of VBA have flip-flopped entirely on this issue. Now the Toast GSM decoder runs slower on recent VBA than on hardware, causing the Halo 2 demo to glitch whenever the player isn't looking straight up.
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