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Demos Amiga Demoscene Archive Forum / Coding / Atari style C2P on Amiga
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sp_
Member
#1 - Posted: 7 Mar 2007 06:17 - Edited
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The blitter pass can be replaced by a 1 CPU merge like this:

(code not tested)
I think the merge can can be optimized by using a rol merge.

input:

;a3a2b3b2a1a0b1b0 e3e2f3f2e1e0f1f0 c3c2d3d2c1c0d1d0 g3g2h3h2g1g0h1h0
;i3i2j3j2i1i0j1j0 m3m2n3n2m1m0n1n0 k3k2l3l2k1k0l1l0 o3o2p3p2o1o0p1p0

Output:

;0,1: a3a2b3b2 c3c2d3d2 e3e2f3f2 g3g2h3h2 i3i2j3j2 k3k2l3l2 m3m2n3n2 o3o2p3p2
;2,3: a1a0b1b0 c1c0d1d0 e1e0f1f0 g1g0h1h0 i1i0j1j0 k1k0l1l0 m1m0n1n0 o1o0p1p0


SMCTABLEC2P:
lea txture1,a0
lea txture2,a1
lea bpl01,a2 ;pointer to bitplane 0 and 1
lea bpl23,a3 ;pointer to bitplane 2 and 3

move.l #$0f0f0f0f,d6

REPT 160*100/32
move.w 0000(a0),d0
or.w 0000(a1),d0 ;ab00
move.w 0000(a0),d1
or.w 0000(a1),d1 ;cd00
move.b 0000(a0),d0
or.b 0000(a1),d0 ;abef
move.b 0000(a0),d1
or.b 0000(a1),d1 ;cdgh
swap d0
swap d1
move.w 0000(a0),d0
or.w 0000(a1),d0
move.w 0000(a0),d1
or.w 0000(a1),d1
move.b 0000(a0),d0
or.b 0000(a1),d0 ;abefijmn
move.b 0000(a0),d1 ;cdghklop
or.b 0000(a1),d1

move.w 0000(a0),d2
or.w 0000(a1),d2
move.w 0000(a0),d3
or.w 0000(a1),d3
move.b 0000(a0),d2
or.b 0000(a1),d2
move.b 0000(a0),d3
or.b 0000(a1),d3

swap d2
swap d3

move.w 0000(a0),d2
or.w 0000(a1),d2
move.w 0000(a0),d2
or.w 0000(a1),d2
move.b 0000(a0),d3
or.b 0000(a1),d3
move.b 0000(a0),d2
or.b 0000(a1),d2

move.l d1,d7
lsr.l #4,d7
eor.l d0,d7
and.l d6,d7
eor.l d7,d0
lsl.l #4,d7
eor.l d7,d1

move.l d0,(a2)+
move.l d1,(a3)+

move.l d3,d7
lsr.l #4,d7
eor.l d2,d7
and.l d6,d7
eor.l d7,d2
lsl.l #4,d7
eor.l d7,d3

move.l d2,(a2)+
move.l d3,(a3)+

ENDR
sp_
Member
#2 - Posted: 7 Mar 2007 06:33 - Edited
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Here is how many cycles extra the MC68000 cpu will use for 32 pixels.

sum= 120 cycles. (15 cycles pr word written to memory.)
A ABCD blitter pass wil use 8 cycles (bus) pr word written.

swap ;4
swap ;4
swap ;4
swap ;4

move.l d1,d6 ;4
lsr.l #4,d6 ;16
eor.l d0,d6 ;4
and.l d7,d6 ;4
eor.l d4,d0 ;4
lsl.l #4,d6 ;16
eor.l d6,d1 ;4

move.l d3,d6
lsr.l #4,d6
eor.l d2,d6
and.l d7,d6
eor.l d4,d2
lsl.l #4,d6
eor.l d6,d3
sp_
Member
#3 - Posted: 7 Mar 2007 07:08 - Edited
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Checked blitter speed now. 8 cycles for each word written with abcd pass.
...
Blitterspeed From the hardware reference manual:

...................n * H * W
time taken.=.-----------
........................7.09 (7.15 for NTSC)

time is in microseconds. H=blitheight,W=blitwidth(#words),n=cycles

n=4+....depends on # DMA-channels used

A: +0 (this one is free!)
B: +2
C or D: +0 In line-mode, every pixel takes 8 cycles.
C and D: +2
sp_
Member
#4 - Posted: 24 Apr 2008 16:06 - Edited
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Bumping this thread

When I started I wanted a fast c2p on the amiga 500. When running in Hires mode on aga computers this c2p can be used to make very fast routines on aga as well. The Scrambled 4bit chunkyformat is ideal. By using self modified code the scramble loop run faster than a byte pr. pixel renderer. Half the bits is pushed directly to chip mem(16 colors).
No c2p ---> 50fps possible.

The three upper bitplanes can be used to make free hardware motionblur.
sp_
Member
#5 - Posted: 13 Dec 2008 17:31 - Edited
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The sourcecode provided in this thread is not compatible with the OCS chipset. The blitterpass need a ECS agnus chip. The reason for this is that the OCS blitter only support copying maximum 64x1024 blocks and this c2p need two blocks of 1x2560 (for a 320x256 2x2 screen) I have fixed this by adding an interrupt que to do more blits. First convert 1x1024 then another 1x1024 and the last 1x512.

On ECS I need 2 blitterpasses, on OCS I need 6. The same amount of data is copied, so the speed is almost equal.

Only 10240 bytes is copied pr frame with ABCD Channel. (160x128 4bpl) Modulo stretched on y-axis and scrollregister/hardware stretched on xaxis.
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