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Old 27 January 2013, 16:57   #1
Toni Wilen
WinUAE developer
 
Join Date: Aug 2001
Location: Hämeenlinna/Finland
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"Interesting" way to detect 68020+ with enabled instruction cache

From Subtle Shades / Nuance bootblock:

Code:
000015D4 47fa 0008                LEA.L (PC,$0008) == $000015de,A3
000015D8 3e3c 012c                MOVE.W #$012c,D7
000015DC 303c 0000                MOVE.W #$0000,D0
000015E0 6614                     BNE.B #$00000014 == $000015f6
000015E2 0c47 0001                CMP.W #$0001,D7
000015E6 6604                     BNE.B #$00000004 == $000015ec
000015E8 36bc ffff                MOVE.W #$ffff,(A3)
000015EC 51cf ffee                DBF .W D7,#$ffee == $000015dc
000015F0 7000                     MOVE.L #$00000000,D0
000015F2 4e7b 0002                MOVEC D0,CACR
000015F6
In my opinion there are much better ways
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Old 27 January 2013, 19:56   #2
StingRay
move.l #$c0ff33,throat

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Location: Berlin/Joymoney
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That code actually makes me smile. There sure are better ways but I have a soft spot for hacks like this.
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Old 28 January 2013, 08:03   #3
musashi5150
move.w #$4489,$dff07e
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Slightly OT but why is SubtleShades ringing a bell for me? Is that the one with the weird problem when using resload_DiskLoad() during the tunnel part Stinger? I haven't got code nearby but I'm 100% I've worked on a WHDLoad installer for this one
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Old 28 January 2013, 11:36   #4
hooverphonique
ex. demoscener "Bigmama"
 
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I see what they're doing, but I don't get why they loop 300 times.. Is the idea that if we spend "enough time" in this piece of code, chances are higher that it will enter the cache?
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