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20 December 2019, 15:57
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#1 |
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It's coming back!
Join Date: Jul 2018
Location: comp.sys.amiga
Posts: 762
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Blitter clearing a line without src channels?
I'm clearing my scratch buffer after drawing a line into it. I don't need to just clear only the bits that have been previously been set, I'm happy to just write entire words full of zeros.
Will I save a tiny amount of time if I just set the minterms to zero and don't enable the C source channel? And if I do, can I also disable the A channel, or will that break the blitter's line drawing algorithm? Will that save me more time? |
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20 December 2019, 18:37
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#2 |
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Lemon. / Core Design
Join Date: Mar 2016
Location: Tier 5
Posts: 1,213
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This is a really interesting question, and one that I don't have the answer to, but will be very interested to know
 thinking outside the box is always great!
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20 December 2019, 18:54
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#3 | |
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Join Date: Jul 2018
Location: comp.sys.amiga
Posts: 762
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Quote:
I can understand requiring A, but I don't see why C would be required. |
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20 December 2019, 19:00
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#4 |
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WinUAE developer
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 49
Posts: 26,553
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20 December 2019, 19:14
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#5 | |
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It's coming back!
Join Date: Jul 2018
Location: comp.sys.amiga
Posts: 762
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Quote:
Ok. |
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10 January 2020, 15:56
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#6 |
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Moderator
Join Date: Nov 2004
Location: Eksjö / Sweden
Posts: 5,652
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I doubt there's a gain or I would have had it in my codebase instead of XOR mode (or possibly 0 mask), because I remember I tried the blocky word linedraw clear back in the day. It seems your only chance is to disable B and measure, and it would be a quick test.
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12 January 2020, 03:42
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#7 |
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Registered User
Join Date: Jan 2012
Location: USA
Posts: 373
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Might setting SING help here? Something I've wondered about is whether or not with SING writes are reduced. If so, then there might be a small amount of time saved blanking lines with slope <1 and >-1 and with minterm set to 0.
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