"Interesting" way to detect 68020+ with enabled instruction cache

Toni Wilen · 27 January 2013, 15:57

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

StingRay · 27 January 2013, 18:56

That code actually makes me smile.

There sure are better ways but I have a soft spot for hacks like this.

musashi5150 · 28 January 2013, 07:03

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

hooverphonique · 28 January 2013, 10:36

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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27 January 2013, 18:56	#2
StingRay move.l #$c0ff33,throat Join Date: Dec 2005 Location: Berlin/Joymoney Posts: 6,863	That code actually makes me smile. There sure are better ways but I have a soft spot for hacks like this.

28 January 2013, 07:03	#3
musashi5150 move.w #$4489,$dff07e Join Date: Sep 2005 Location: Norfolk, UK Age: 42 Posts: 2,351	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

28 January 2013, 10:36	#4
hooverphonique ex. demoscener "Bigmama" Join Date: Jun 2012 Location: Fyn / Denmark Posts: 1,637	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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