Amiga 1200 020 + fastram vs blitter

[sandruzzo]

On Amiga 1200 with fast ram, is 020 fast enough to help blitter on restore screen after cookie-cut blitter operation?

Is it worth using 020 to draw tiles for scrolling? I would like to use 020 with fast mem for vertial scrollin,g and blitter for bobs on 8 planes screen.

Thanks

[DanScott]

Personally, I would try to get something working as fast together (020 & Blitter) without requiring fast mem

[sandruzzo]

Originally Posted by DanScott

Personally, I would try to get something working as fast together (020 & Blitter) without requiring fast mem

There is a why I want use fast mem

[Lazycow]

In Tubular Worlds, the tilesize is 8x8 pixels and the CPU updates the borders for scrolling. (obviously, it's fast enough)
For vertical scrolling on top or bottom only 1 pixel line is updated.
For horizontal scrolling one 32x8 pixel block (4 tiles) is updated on the left or right. (the bitmap is bigger than the visible screen)
The 4 tiles are written with move.b (a0)+,offset(a1)
Then the data is copied with movem.l to registers and written back to two different bitmaps again with movem.l (it's tripple-buffered).

It's pretty fast if you only update the borders... (...and use the abilities of the Amiga chipset for scrolling)
This worked for 256 colors on AGA/020/chipmem-only and for 32 colors with standard 68000.

[Photon]

Originally Posted by sandruzzo

On Amiga 1200 with fast ram, is 020 fast enough to help blitter on restore screen after cookie-cut blitter operation?

Is it worth using 020 to draw tiles for scrolling? I would like to use 020 with fast mem for vertial scrollin,g and blitter for bobs on 8 planes screen.

Thanks

So, 2 questions at once!

I don't think it's unnatural to require Fastmem on a stock A1200. Most users will have gotten something to get them past the 2MB chipmem limit, even if it's not a 100-150 EUR accelerator.

1. The 020 can certainly restore the background quickly in cases of f.ex. 16x16 bobs. What method you used to modify the bitmap areas (to be restored) doesn't matter. What matters is keeping the width of objects the same, and just save "coordinates" of areas to restore. If the width differs, you have to make a loop that handles it which gives quite a bit of overhead.

2. You should use the Copper and set bitplane pointers in order to scroll vertically, that way it will take no time at all. Do not scroll by copying memory on Amiga, ever. Ever! I keel you!

To plot tiles, often the CPU is faster than the Blitter, even on 68000, so no problem there

[DanScott]

Originally Posted by Photon

To plot tiles, often the CPU is faster than the Blitter, even on 68000, so no problem there

Definitely, if you only need to plot 1 or 2 pixels of tiledata (the blitter "setup" would take longer than just writing the data straight to the screen memory)