I think a small deficiencie of the AMIGA blitter is that it can not reuse one of its sources.

The AMIGA Blitter is perfect for copying BITMAPS and masking them.
You can use the AMIGA BLITTER perfectly to opaque copy memory and to blit BOBS.

To copy a BOB the AMIGA Blitter needs to use 3 SOURCES and 1 DESTINATION.

SRC A = Background
SRC B = BOB
SRC C = BOB-MASK
DST  = Background write again

This works fine.
Only to be able to copy BOBS which multiply planes -
You either need to start the blitter one time per plane.
Or you need to have a BOB-MASK that doublecated per plane.
The first is more overhead - the last wastes memory.
If one SRC could loop then you could copy a BOB with one go without the need of more memory.

Cheers

I am not explaining this correctly but that is because i haven't slept.
Shame on me but i need to have more hours i a day to finish me work. :(

I think Caching and besides that still buffering would be a advantage here.

A cache would NOT help here.

The point was to reduce the memory requirement for BOBS that use interleave bit plane mode.
 

A cache for the blitter is bad because of a number of reasons.
A) A cache has the tremendous disadvantage of being very expensive  in HW.
B) We have only a limited amount of cache resources - to give the Blitter a cache you would have to steal it from the 3D core.
C) A cache for the blitter is difficult to do as it needs to be write able too.

Instead doing very complex way that give more work than benefit we should focus on the small elegant solutions.

Please let us loook for good improvements which we could for little HW investment.

The copper's purpose is to write to the other custom chips. For example telling the blitter to write something to memory, or changing a color in the current palette.
The copper does this by waiting for a certain beam position being drawn on the screen, and what it is supposed to wait for and what custom chip register it should write to is decided by the programmer in a copper list.

Because it is only writing to the custom chip registers (and cannot write elsewhere in RAM by itself), it wouldn't need more/bigger registers if there aren't hundreds of new custom chip registers that need to be addressed.

A copper that can write anywhere in RAM would be cool, but the way Amiga is built is having the copper telling the blitter to do so.

About the idea itself: anything that can improve 2D performance is worth having a look at in my book! :D

Hi Gunnar,

if you maybe could explain a bit more detailed what exact kind of screenmode you are targeting? I got a bit confused about your description. I have rough suspicions about your aim, maybe if you clarify further, I may be of help.

Claudio

@Gunnar
I think the idea of putting a counter on the mask plane is a great idea.  It will allow us to reuse the mask plane's contents for all of the bitplanes per row to work.  The disadvantage of this approach is that we'd have to cut up the BOBs into memory access width swaths to take advantage of the interleave rather than using the full width.  It adds a little complexity but I think it's worth it.

On AMIGA you could have interleaved or non-interleaved bitmap screens.
Interleaved bitmaps had the advantage that you could copy 1 bob with 1 Blitter call. But to only use 1 call you needed a mask that repeated itself for all the SRC planes.

On non interleaved planer screens you needed for one Bob 1 Blitter call per plane - But you only needed a 1 plane mask. This did save memory.

My proposal was to add a loop counter to the blitter allowing it to stay ion the MASK and to only add the MODULA ádd the next line and not after each plane. This would combine the advantages of both PLANAR types. Only 1 Blitter call needed but small MASK.

My example was planar only.
While the normal AMIGA Blitter could also be used for CHUNKY modes - some new features might come even more handy for chunky modes. As for example the 3Dcore could be used to blit BOBS and to rotate them for free ....

What if MASK was a pointer to a list of pointers (for each plane).

@MASK
-----
MASK0
MASK1
...
MASK7

The Blitter would read this list at the start of the copy and set up 8 internal pointers for each plane. The idea here is that you COULD specify unique non-interleaved masks for each plane for some possible effects (though I can't think of any practical uses right now).

Nice idea but this would be a bigger change.
My idea would only be a very small change.
It would only add a 3bit register to the blitter.
But it would reduce the size of a 8 plane interleaved bob by 45%.

Small change with relative big effect - and the behavior is fully backward compatible.

There may be as many as 1,000 math formulae that started life this way....

The main advantage of planar was that you could save memory on low color screens. But this advantage is not important anymore.

A general advantage of the AMIGA chipset is that you could scroll for free. On a PC you needed to copy the whole screen to scroll it.
The free scolling advantage of the AMIGA chipset is valid to both the old PLANAR and the new SuperAGA chunky modes.

Chunky has some advantages.
A) Cookie Cut Bobs. To copy a BOB you need no mask anymore but could select the transparence with a color. This saves memory and makes copying faster.
B) 3D or rotation effects need where you set each pixel individually - are much better to do on CHUNKY then on PLANAR.

For a new game I would propably pick a 16bit chunky mode as it easier to paint GFX for and easy to use.

I really think that it would be good to try to get the developper board out as soon as possible and the consumer board on July the 24th 2010, the 25th anniversary of the Amiga 1000. Releasing the consumer version on that date can be used as a marketing element.

Adding this feature or any new Chipset feature is independent of the board release date.

The board release date is only depending on the dates when the mainboard design is finished and when the mainboards are manufactured.

By design the Natami chipset can always (at any time) be updated with new features by loading them into the chipset.

I think the upgradebility of the Natami is its beauty.
The mainbaord has a flash which contains its setting.
(Like the Kickstart disk of the A1000)
Installing a new chipset with more features is possible at any time.

Cheers