Missing Display modes

[sandruzzo]

@pandy71

yes, you can do 6 plane blit in one shot, but you use more dma cycles on cookie-cut operation, since blitter have to load mask every time.

- copper was good, but in my opinion with few tweak could have done more. Move operation waste to much time if you have to load sequencial register

[coder76]

AGA does have colorbank swap option via bplcon4, so you can swap colorbanks in sizes of 2^n with a single instruction in copperlist. That means you can preload 256 colors in color registers, and if you have eg. a 32-color display, you can have 7 other 32-color banks that can be swapped as active bank. This is handy as you dont need to write each color separately as in OCS, but there is of course a 256 color limit. This also puts an end to copper color clashes, as you can change anytime unused color banks, and have active bank untouched.

[pandy71]

Originally Posted by coder76

AGA does have colorbank swap option via bplcon4, so you can swap colorbanks in sizes of 2^n with a single instruction in copperlist. That means you can preload 256 colors in color registers, and if you have eg. a 32-color display, you can have 7 other 32-color banks that can be swapped as active bank. This is handy as you dont need to write each color separately as in OCS, but there is of course a 256 color limit. This also puts an end to copper color clashes, as you can change anytime unused color banks, and have active bank untouched.

True but seem some limitations exist and we talking on 15 or 16 bit address (so up to 256 banks of 256 color registers).
not sure if i recall correctly but Toni mention some limitations in HAM mode (BANK not work?). Sorry if i mixed something.

Btw - forgot to add to my list support to alternative colour space (something Like YCgCo) - it could accelerate video decoding but also (perhaps) improve HAM behaviour.

Another idea is 7 bit HAM mode where upper 3 bits works like RGB mask.

[FSizzle]

Originally Posted by sandruzzo

yes, you can do 6 plane blit in one shot, but you use more dma cycles on cookie-cut operation, since blitter have to load mask every time.

A single 6 plane interleaved blit with mask or 6 individual blits with mask takes the same amount of blitter DMA cycles. The interleaved blit requires that you duplicate all the lines in your mask so the modulo matches the source.

So the tradeoff is using a lot more memory (almost double) for the source data, but the saving is on blitter setup/wait loops.

It is a shame there is no way to have a mask that is re-used multiple times for the N lines of source data, as this would make masked blits use almost 25% fewer DMA cycles.

[sandruzzo]

Originally Posted by FSizzle

A single 6 plane interleaved blit with mask or 6 individual blits with mask takes the same amount of blitter DMA cycles. The interleaved blit requires that you duplicate all the lines in your mask so the modulo matches the source.

So the tradeoff is using a lot more memory (almost double) for the source data, but the saving is on blitter setup/wait loops.

It is a shame there is no way to have a mask that is re-used multiple times for the N lines of source data, as this would make masked blits use almost 25% fewer DMA cycles.

With 6 blits whiout cpu aid, you can chace mask and spare a lot of dma cicles

[FSizzle]

Originally Posted by sandruzzo

With 6 blits whiout cpu aid, you can chace mask and spare a lot of dma cicles

I'm don't understand what you mean. Do you mean there is some way to do this on current hardware? Or do you mean on some hypothetical hardware it would be possible?


Can you explain a bit more please?

[sandruzzo]

Originally Posted by FSizzle

I'm don't understand what you mean. Do you mean there is some way to do this on current hardware? Or do you mean on some hypothetical hardware it would be possible?


Can you explain a bit more please?

Only missed opportunity on OCS. It could be done very easly. If you use fixed mask, you can do it now