Search found 18 matches
- Wed Mar 05, 2014 6:23 pm
- Forum: Megadrive/Genesis
- Topic: 68k signed division problems (DIVS instruction)
- Replies: 9
- Views: 6572
And don't use divide on powers of two - use the arithmetic shift instead (unless you need the remainder). If you need the remainder, you use a logical "and" :D Well, you also need to worry about the sign, but that's certainly still faster than the mega-slow divide on the 68000. :D Is it really that...
- Fri Feb 28, 2014 7:29 pm
- Forum: Megadrive/Genesis
- Topic: 68k signed division problems (DIVS instruction)
- Replies: 9
- Views: 6572
Chilly Willy you are AWESOME! That was it! Apparently the manual I've been reading doesn't mention that ( http://courses.ece.ubc.c/259/Summary%2068000%20Instruction%20Set.pdf Page 21 doesn't mention that). From now on I'll just stick to the "M68000 Family Programmer's Reference Manual" Thank you :D ...
- Fri Feb 28, 2014 6:10 pm
- Forum: Megadrive/Genesis
- Topic: 68k signed division problems (DIVS instruction)
- Replies: 9
- Views: 6572
68k signed division problems (DIVS instruction)
Hello everyone. I haven't been active here for.. a long time. I just started working on a small Sega CD program (Yes, this is the Genesis forum but the problem I'm about to talk about has to do with the main M68K processor and nothing involving SCD hardware) So I've created a simple system for showi...
- Sat Apr 02, 2011 12:57 am
- Forum: Mega/SegaCD
- Topic: Scaling hardware?
- Replies: 84
- Views: 79657
So, I've been thinking a lot about it, and maths seem to be needed for rotation. And I SUCK at maths. The main problem is determining the delta values for each angle, so that the image keeps its correct size. I've been trying to understand how I could do this and this is how I understand it so far: ...
- Thu Mar 31, 2011 6:28 pm
- Forum: Mega/SegaCD
- Topic: Scaling hardware?
- Replies: 84
- Views: 79657
- Thu Mar 31, 2011 6:19 pm
- Forum: Mega/SegaCD
- Topic: Scaling hardware?
- Replies: 84
- Views: 79657
Wow. Thank you, so much. I think you'd tried to explain me this some other time. But now I really get it. It's still quite a mess to rotate an image, or scale it, lots of coding headache for me, yay. It's funny to think that when I first heard of the Mega CD and its scaling/rotation capabilities, I ...
- Wed Mar 30, 2011 12:15 am
- Forum: Mega/SegaCD
- Topic: Scaling hardware?
- Replies: 84
- Views: 79657
Scaling hardware?
Has anyone here managed to actually do something with it? I just seriously DON'T UNDERSTAND the principle the way it is explained on the documents..
- Thu Aug 13, 2009 1:41 am
- Forum: Megadrive/Genesis
- Topic: How do I compile something here? [solved]
- Replies: 8
- Views: 6422
- Sun Jun 14, 2009 4:42 am
- Forum: Mega/SegaCD
- Topic: Huh? Are there TWO Int2 entries on the jumptable?
- Replies: 8
- Views: 8537
- Fri Jun 12, 2009 11:00 pm
- Forum: Mega/SegaCD
- Topic: Huh? Are there TWO Int2 entries on the jumptable?
- Replies: 8
- Views: 8537
Yeah I've been told about that, now......... Okay, I think the problem is basically..me I don't know these terms: V-int Handling Int2 Handling Interrupt processing I don't know what "handling" would mean. All I know about interrupts is: You setup some entry, when the exception happens, the 68000 jum...
- Fri Jun 12, 2009 2:43 pm
- Forum: Mega/SegaCD
- Topic: Huh? Are there TWO Int2 entries on the jumptable?
- Replies: 8
- Views: 8537
Hey, thank you two. But, about the Int2, I still don't get it :( . At least now it doesn't crash, it just keeps doing what it should(Sub-CPU side) On the main-cpu side.. I can't setup Vblank: I first disable all the interrupts Then I write to $FFFD08 Then.. I enable interrupts 6 and 7 (sr is $2500) ...
- Fri Jun 12, 2009 1:33 am
- Forum: Mega/SegaCD
- Topic: Huh? Are there TWO Int2 entries on the jumptable?
- Replies: 8
- Views: 8537
Huh? Are there TWO Int2 entries on the jumptable?
Hi everybody. Em.. I noticed something which is.. frustating me. You know, the BIOS manual says that Int2 entry should not be changed since BIOS uses it. But, I just found that there are two Int2 entries? WTF? And Sonic CD changes these two.Why, weren't these supposed not to be changed? $5F34: It's ...
- Mon Jun 08, 2009 10:24 pm
- Forum: Blabla
- Topic: I cannot access some of this forum ?
- Replies: 12
- Views: 9421
- Fri Jun 05, 2009 3:12 am
- Forum: Mega/SegaCD
- Topic: CDROM reading issue after subcpu halt
- Replies: 30
- Views: 43036
- Fri Jun 05, 2009 3:08 am
- Forum: Mega/SegaCD
- Topic: Entries address, function number
- Replies: 8
- Views: 10550