Search found 237 matches

by powerofrecall
Mon Sep 12, 2016 7:00 pm
Forum: Megadrive/Genesis
Topic: Line scroll & VDP mode regs
Replies: 4
Views: 676

Re: Line scroll & VDP mode regs

I ended up splitting my line scroll buffer in RAM into two contiguous buffers for each plane which are then interleaved into VRAM through a couple of offset DMAs. Speed isn't a problem so far because my game logic isn't that complex yet, but I like the idea of using the full plane scroll in hblank t...
by powerofrecall
Mon Sep 12, 2016 4:29 pm
Forum: Megadrive/Genesis
Topic: Line scroll & VDP mode regs
Replies: 4
Views: 676

Line scroll & VDP mode regs

If I'm doing a split scroll background with line scroll, do I absolutely have to fill out the entire horizontal scroll RAM per line? It seems pretty wasteful to have to fill it out for every single line when most of the values are duplicated. Especially when I have 2 or 3 "row" splits (VDP's in line...
by powerofrecall
Thu Jul 14, 2016 3:01 am
Forum: Blabla
Topic: It seemed
Replies: 8
Views: 1885

Re: It seemed

I own the "Mario" version. It's a good multicart & I got a chuckle out of the name too, wonder if they were... inspired by this site?
by powerofrecall
Thu Jul 14, 2016 2:49 am
Forum: Megadrive/Genesis
Topic: Infinite scrolling maps/scroll plane "edge" DMA
Replies: 15
Views: 1866

Re: Infinite scrolling maps/scroll plane "edge" DMA

A good easy to implement fast RLE is the "mac packbits" format https://en.wikipedia.org/wiki/PackBits C packer source is available at https://pineight.com/nes/ under "pin eight NES tools" Here's an unpacker, in C (this would be real easy to write in 68k though), that I have been using for nametables...
by powerofrecall
Fri Jun 17, 2016 2:30 am
Forum: Megadrive/Genesis
Topic: Infinite scrolling maps/scroll plane "edge" DMA
Replies: 15
Views: 1866

Re: Infinite scrolling maps/scroll plane "edge" DMA

Sik wrote:Dragon's Castle
Oh by the way Dragon's Castle is excellent and definitely an inspiration for me to keep going. I'm very impressed it's in 68k, I am terrible at writing logic type stuff in assembly.
by powerofrecall
Fri Jun 17, 2016 2:26 am
Forum: Megadrive/Genesis
Topic: Infinite scrolling maps/scroll plane "edge" DMA
Replies: 15
Views: 1866

Re: Infinite scrolling maps/scroll plane "edge" DMA

Well, for Dragon's Castle I'm using Tiled, though you need to use some specific settings to have it work (more specifically, I have a converter script that takes the TMX file and turns it into the game's format, and it does so in a rather lame and lazy way). Still probably good enough to work I sup...
by powerofrecall
Thu Jun 16, 2016 9:24 pm
Forum: Megadrive/Genesis
Topic: Infinite scrolling maps/scroll plane "edge" DMA
Replies: 15
Views: 1866

Re: Infinite scrolling maps/scroll plane "edge" DMA

By the way, if your tilemap is 64 tiles wide (i.e. 64×32 or 64×64) then you can set autoincrement to $80 to draw tiles vertically, so you can load a whole column with a single transfer. Good to know this will work the way I thought it would! EDIT: also you don't store the nametable as-is, that's ri...
by powerofrecall
Thu Jun 16, 2016 6:57 pm
Forum: Megadrive/Genesis
Topic: Infinite scrolling maps/scroll plane "edge" DMA
Replies: 15
Views: 1866

Infinite scrolling maps/scroll plane "edge" DMA

I want to 8-way "infinite" scroll a plane, presumably by reloading the plane's nametable at just past the edge of the visible screen. What's the generally accepted way to accomplish this? Assume I have two functions, both that do a DMA to copy either a 40 tile wide "row" or a 32 tile high "column." ...
by powerofrecall
Sat May 28, 2016 12:11 am
Forum: Hardware
Topic: Hmmmm.......?
Replies: 25
Views: 5106

Re: Hmmmm.......?

This is sexy, I want one.
by powerofrecall
Tue Apr 26, 2016 8:14 pm
Forum: Megadrive/Genesis
Topic: Alright dudes, I need your help! (soft-reset bug)
Replies: 37
Views: 3374

Re: Alright dudes, I need your help! (soft-reset bug)

Looking at the vasm manual, it looks like optimizing move #0, <ea> to clr <ea> is only enabled default if you tell it that you're targeting something newer than a 68000. Are you passing -m68000 to vasm? Yeah, -m68000 is getting passed to vasm and -cpu=68000 is getting passed to vbcc. Also tried -no...
by powerofrecall
Tue Apr 26, 2016 6:35 pm
Forum: Megadrive/Genesis
Topic: Alright dudes, I need your help! (soft-reset bug)
Replies: 37
Views: 3374

Re: Alright dudes, I need your help! (soft-reset bug)

Plus using a modern GCC to build Genesis stuff felt not unlike using a shotgun to swat a fly, you know? Is it? I know Sega used GCC for the Saturn, I wouldn't be surprised if GCC was also an option with the Mega Drive. Really the only difference is that you'd be using a newer version of the tool in...
by powerofrecall
Tue Apr 26, 2016 6:01 pm
Forum: Megadrive/Genesis
Topic: Alright dudes, I need your help! (soft-reset bug)
Replies: 37
Views: 3374

Re: Alright dudes, I need your help! (soft-reset bug)

This is beginning to drive me a little crazy. The source emitted by the compiler contains move.l #0,(a1), manually assembling that with -no-opt generates a listing file that also contains move.l #0,(a1), but something about the process of compile->assemble-> link it is getting "optimized." No comman...
by powerofrecall
Tue Apr 26, 2016 5:56 pm
Forum: Megadrive/Genesis
Topic: Alright dudes, I need your help! (soft-reset bug)
Replies: 37
Views: 3374

Re: Alright dudes, I need your help! (soft-reset bug)

r57shell wrote:btw joypad & dma should be in same gemsdmastart() gemsdmaend() block.
You don't need to stop z80 for joypad. All you need is guarantee no access to m68k bus. That is done by this funcs.
I saw this in that Gargoyles source dump and thought it was kind of strange but I guess it makes sense
by powerofrecall
Tue Apr 26, 2016 5:38 pm
Forum: Megadrive/Genesis
Topic: Alright dudes, I need your help! (soft-reset bug)
Replies: 37
Views: 3374

Re: Alright dudes, I need your help! (soft-reset bug)

No matter WHAT I tell the assembler to do it insists on generating clr.l (a1). This is what I meant by bad documentation, there's probably something I'm not doing right.
by powerofrecall
Tue Apr 26, 2016 5:26 pm
Forum: Megadrive/Genesis
Topic: Alright dudes, I need your help! (soft-reset bug)
Replies: 37
Views: 3374

Re: Alright dudes, I need your help! (soft-reset bug)

Unfortunately, compilers are not always compliant (especially ones for architectures that have fallen out of favor). Ironically, this is one of the main reasons I went with vbcc in the first place. It's still actively getting worked on, even if it is a little rough around the edges, and 68k is pret...