Search found 451 matches

by Dio
Sun Aug 04, 2013 11:00 am
Forum: Games - General
Topic: Graphics and Map ripping from Atari ST games
Replies: 29
Views: 7791

Re: Graphics and Map ripping from Atari ST games

As you say, the problem with these minimal snapshots is that you're actually loading the program in an undefined state. To an emulator author that's a bit pointless really. The purpose of savestates is to let people save (at arbitrary time) and keep going, to enable rewind support and (critically) t...
by Dio
Sun Aug 04, 2013 10:25 am
Forum: Coding
Topic: Palette register address in Dungeon Master and CSB
Replies: 16
Views: 4958

Re: Palette register address in Dungeon Master and CSB

I'm fairly sure there is direct FDC access in Dungeon Master, at least, IIRC to read a $F7 sector hidden on track 1 or the bad bits in one of the other sectors. It's done in a fairly well obfuscated manner though, as are all DM's and CSB's protection checks. But I may have misremembered...
by Dio
Thu Aug 01, 2013 10:29 pm
Forum: Coding
Topic: Palette register address in Dungeon Master and CSB
Replies: 16
Views: 4958

Re: Palette register address in Dungeon Master and CSB

It uses fewer CPU cycles to use $FFFF8240, because that address can be accessed using absolute word addressing rather than absolute long. So in a typical palette-setting routine: lea source, a0 lea $FFFF8240.w,a1 / lea $FF8240,a1 move.l (a0)+,(a1)+ ; x8 The absolute word version is 2 bytes and 4 cyc...
by Dio
Thu Aug 01, 2013 10:25 pm
Forum: Chat forum [ENG]
Topic: The birth of Atari ST
Replies: 33
Views: 7771

Re: The birth of Atari ST

Possibly in mainland Europe - but AFAICS in the UK the ST was mostly a games machine. The Amiga was far too expensive for the main gamers market of the time (schoolkids). In the same way that only the rich kids had C64s (until the 8-bits were already dead), the Amiga was simply too much of a stretch...
by Dio
Wed Jul 31, 2013 10:35 pm
Forum: Games - General
Topic: Graphics and Map ripping from Atari ST games
Replies: 29
Views: 7791

Re: Graphics and Map ripping from Atari ST games

I don't get why you talk about some 'hidden state' in case of ST. There is nothing hidden (except maybe wake-up states, which are not interesting at all in this case) . Everything can be read. All HW registers. Only that with MFP Timer data registers is little harder. If you're considering stopping...
by Dio
Wed Jul 31, 2013 10:22 pm
Forum: Chat forum [ENG]
Topic: The birth of Atari ST
Replies: 33
Views: 7771

Re: The birth of Atari ST

My thoughts: I still think both Atari's failures and the PC quality bang killed Atari off..... The Megadrive largely killed the ST and Amiga as games machines; for 80% plus of game titles it offered hugely better quality at a vastly cheaper (hardware) price because of the platform fee model, and mor...
by Dio
Sun Jul 28, 2013 10:41 pm
Forum: Games - General
Topic: Graphics and Map ripping from Atari ST games
Replies: 29
Views: 7791

Re: Graphics and Map ripping from Atari ST games

Basically, the problem is that unless there's a strict definition of exactly what the 'hidden state' in the ST is, then it's impossible to write a portable savestate file, and I'm not sure that we have that strictly nailed down for the ST yet (although the FPGA ST efforts may reveal it, if they've b...
by Dio
Fri Jul 26, 2013 9:32 pm
Forum: Games - General
Topic: Much more could have been done on ST
Replies: 63
Views: 9819

Re: Much more could have been done on ST

nativ wrote:earliest cut scene? Ms.Pacman ? or Pacman?

Donkey Kong climbing to the top of the building and jumping?
by Dio
Wed Jul 24, 2013 10:32 am
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

If you're disabling transfer to protect an event, you need to disable the transfer at least 1ms before the event occurs or a byte may already be in flight.
by Dio
Tue Jul 23, 2013 10:35 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

With the interrupt re-enable code right at the start, the worst case Timer B interrupt latency should increase by about 60 cycles.
by Dio
Mon Jul 22, 2013 10:02 am
Forum: Games - General
Topic: Much more could have been done on ST
Replies: 63
Views: 9819

Re: Much more could have been done on ST

The 1984 video game crash was largely a US phenomenon. At the very least, it didn't affect the UK - 1983-86 were the strongest years of the 8-bit systems. The UK 'crash' came later, and it was less a consumer crash (consumers made an easy transition from awkward disks and expensive computers to simp...
by Dio
Sat Jul 20, 2013 5:32 pm
Forum: Games - General
Topic: Much more could have been done on ST
Replies: 63
Views: 9819

Re: Much more could have been done on ST

I'll concede that it's worst is better than the ST's worst. But it's a strength and a weakness; sacrificing individual innovation for corporate quality. Sure, I have a bias against it since I consider platform games extremely tedious, and it's a system that didn't do an awful lot else original. But ...
by Dio
Sat Jul 20, 2013 4:22 pm
Forum: Games - General
Topic: Much more could have been done on ST
Replies: 63
Views: 9819

Re: Much more could have been done on ST

It's a gross generalisation, but what does the NES have apart from crappy arcade ports? The ST (and Spectrum) were creative machines. The NES wasn't. It also certainly wasn't heavily imported to the UK. I worked at a shop selling mostly console imports for a while and the NES didn't figure on the ra...
by Dio
Wed Jul 17, 2013 12:56 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

Good point. You could probably write 3 to FFFFFC04, which would lock the MIDI ACIA off.

I am somewhat concerned that the code should care about the order of those two operations. Does it work the other way around if you leave out the move to SR?
by Dio
Wed Jul 17, 2013 10:44 am
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

The ISR bit should be cleared immediately before the RTE, not before setting $118, or there's a possible race there. You can also add a lot of .w to your fffffa11s and $118s for additional speedups and smaller code. Also be aware that the keyboard will lock if you ever receive a byte via midi and th...
by Dio
Tue Jul 16, 2013 4:07 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

I removed the "hook onto the old IKBD" code and now the routine didn't work, so I put in the "move.b "$bf,$fffa1" at the end and now everything seems to work fine! Right, that's all the OS routine was doing for you. You have to clear that ISR bit or you'll never see another...
by Dio
Tue Jul 16, 2013 11:16 am
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

If you're using the BIOS routine to just hook joystick control then you don't need to worry about anything beyond writing d0 where you want it to go. If you're doing anything with the ACIA and MFP directly then you have to do it all and cut the BIOS out. There's no way to have two different systems ...
by Dio
Mon Jul 15, 2013 5:18 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

The MFP is a full interrupt controller. It has 16 interrupt priority levels each of which can be made pending and have interdependent priority even when other interrupts are in service. The MFP IER controls interrupt enable. If that bit is 0, interrupts on the channel are ignored. Otherwise, when an...
by Dio
Mon Jul 15, 2013 2:50 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

I guess the routine that sets $118 with a new address for each state is more efficent than mine since I have alot of compares, jumps in it. Yes. But it's only saving a couple of branches through a jump table, and as I noted, I'm not certain it's 100% reliable. (Jumptable methods can also be larger,...
by Dio
Mon Jul 15, 2013 1:41 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

You have to check fffc000. In fact, you have to check fffc004 as well. The interrupt on the MFP is edge-triggered, so if it stays low then the interrupt is not signalled again. So, to give the simplest example, if you see an interrupt, read the keyboard, and do nothing else, and it's in fact a MIDI ...
by Dio
Mon Jul 15, 2013 11:39 am
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

Ok, so I should check bit 0 in fffc00 first to see if there is anything here and if so, read fffc02 and if it's a keyboard code, just handle the value as it is, or if it's a joystick package, read fffc00 again to see if more is coming and fffc02 and so on....? You can't do a waiting routine, unless...
by Dio
Mon Jul 15, 2013 8:56 am
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

Nyh's method there is using the interrupt vector to manage the state machine. It's a valid method, although not without issues: - the init code clobbers the existing MFP configuration fairly heavily, so if you use that unmodified other things will probably stop working - I think it suffers the probl...
by Dio
Mon Jul 15, 2013 7:02 am
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

The top routine works. The bottom routine doesn't. If you use them together, then you disable the OS routines entirely and the joystick will cease to work. The keyboard will kind-of work but very unreliably (and will lock up at the slightest provocation). The IKBD communicates with the CPU via a ser...
by Dio
Sun Jul 14, 2013 4:39 pm
Forum: 680x0
Topic: IKBD Keyboard Joystick trouble
Replies: 28
Views: 6933

Re: IKBD Keyboard Joystick trouble

I'm reasonably confused by what you're trying to do here. I don't understand the 'lower keyboard priority below HBL' - that isn't possible in the ST. And I don't see the state machine in your interrupt routine that is required to parse the IKBD command stream, so I don't see how you'll treat joystic...
by Dio
Sun Jun 30, 2013 7:54 pm
Forum: MIDI Software and Hardware
Topic: Cubase Audio Dongle Clone
Replies: 130
Views: 69493

Re: Cubase Audio Dongle Clone

But the cubase guys weren't stupid and it's everything but simple to figure out that exactly is done with the dongles reply. I've thought about this when trying to add extra debugging capabilities to an emulator. It is possible to add extra tracing information to a CPU core. You can 'colour' values...

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