Search found 97 matches

by alien
Wed May 11, 2016 1:04 am
Forum: Coding
Topic: ST Chipset decap
Replies: 144
Views: 77685

Re: ST Chipset decap

Below is a seudo simulation waveform of the 4-bit hard scroll. NOTE: the timing is not exact . This is just for the purpose of illustrating the idea of the K offset. Seudo-4bit.png The two vertical guides mark the moment that the resolution changed. First from mono to medium, then to low. Between b...
by alien
Wed May 11, 2016 12:38 am
Forum: Coding
Topic: ST Chipset decap
Replies: 144
Views: 77685

Re: ST Chipset decap

By the way, I am not completely sure that K is always the same, are we? There might be a wake up effect that could move K by half a cycle (one med rez cycle). I think we are -- my articles say K = 1, and I don't remember seeing any variation on that. By the way two: Is this very stable? I mean, it ...
by alien
Fri May 06, 2016 10:02 pm
Forum: Coding
Topic: ST Chipset decap
Replies: 144
Views: 77685

Re: ST Chipset decap

My 4 bit hardscroll had a weird feature: it was offset by k+4n pixels versus the normal beginning of a line (n = 0, 4, 8, 12). Because k wasn't 0, (but small, although I don't remember the value), one couldn't transition from high to low at the beginning of each line when n=0 (corresponding to not s...
by alien
Thu Mar 31, 2016 5:10 am
Forum: Coding
Topic: ST Chipset decap
Replies: 144
Views: 77685

Re: ST Chipset decap

ijor wrote:I will use this thread to post WIP details of my work on reverse engineering the ST custom chipset by layout inspection and analysis.


Cool! Looking forwards to reading this!
by alien
Thu Mar 31, 2016 4:21 am
Forum: Coding
Topic: Sync-tricks/fullscreen discussion
Replies: 117
Views: 50155

Re: Sync-tricks/fullscreen discussion

Another hypothesis would be that the counters are not initialized at powerup, and therefore can be in one of 4 states ... I'm curious whether you have evidence for either hypothesis. Hi Alien, That was mi initial hypothesis as well. Mainly because I HAD NO IDEA that those chips implement power-up l...
by alien
Wed Mar 23, 2016 3:43 am
Forum: Coding
Topic: Sync-tricks/fullscreen discussion
Replies: 117
Views: 50155

Re: Sync-tricks/fullscreen discussion

Each one of these chips has a two bits counter that clocks its respective process. The counters are not affected by hardware reset. This is by design because the processes are not completely stopped during Reset. The counters then are initialized at power up time only. There is no board level power...
by alien
Mon Feb 15, 2016 5:26 am
Forum: Demos - General
Topic: demogroups galaxy
Replies: 39
Views: 34174

Re: demogroups galaxy

1/ Alien, your technical point of view of the Fullscreen Do you mean your upper/lower overscan in the github core.s file? I found your use of "NO_BORDER" confusing since by that you mean leaving all borders. I didn't check the code in detail, but upper/lower overscan's pretty simple excep...
by alien
Thu Jan 14, 2016 4:29 pm
Forum: Hardware
Topic: best LCD monitor working with ATARI SCART
Replies: 26
Views: 11153

Re: best LCD monitor working with ATARI SCART

Thanks Troed!
by alien
Thu Jan 14, 2016 2:59 am
Forum: Demos - General
Topic: demogroups galaxy
Replies: 39
Views: 34174

Re: demogroups galaxy

Hi Alien, I made an article for the french magazine Programmez! about the Atari ST and the community. With Zerkman, we maybe plan an another article about fullscreen synchronisation and sync lock explanations and I know you are the best people to talk about. And it's in english, of course I can tra...
by alien
Thu Jan 14, 2016 2:52 am
Forum: Demos - General
Topic: demogroups galaxy
Replies: 39
Views: 34174

Re: demogroups galaxy

Any chance we get a preview? If I get the time to get a new monitor up and running, and if my SyQuest 44Mb cartridges are still readable, perhaps... Also would like to see if my overscan Pacmania code is still recoverable (the demo I originally started for the Punish Your Machine but had to abandon...
by alien
Thu Jan 14, 2016 2:46 am
Forum: Hardware
Topic: best LCD monitor working with ATARI SCART
Replies: 26
Views: 11153

Re: best LCD monitor working with ATARI SCART

@Troed: does the dell let you see the edges of the screen in overscan (including the black stabiliser, and the data that follows it)?
by alien
Wed Jan 13, 2016 7:32 pm
Forum: Demos - General
Topic: demogroups galaxy
Replies: 39
Views: 34174

Re: demogroups galaxy

Unfortunately you guess correctly. Ajrarn made a nice level editor for it, which ATM got to play with I believe, and I had hardscrolling + soundtracker + 6301 code + the main ship sprite working for it, but little gameplay -- I did a lot of work on waitstates for it for instance. But, University and...
by alien
Wed Jan 13, 2016 4:11 pm
Forum: Pasti & VAPI
Topic: Ghouls and Ghosts Copy Protection
Replies: 6
Views: 17877

Re: Ghouls and Ghosts Copy Protection

He did a track read. Tracks don't just contain the data of sectors, but also synchronization information, sector headers and gaps. As Markus Fritze said, the type of track on the disk cannot be written with a standard Atari ST. Psygnosis used a similar protection some of their early games. IIRC the ...
by alien
Wed Jan 13, 2016 4:05 pm
Forum: Demos - General
Topic: demogroups galaxy
Replies: 39
Views: 34174

Re: demogroups galaxy

ATM also was the link between ST Connexion and Naos. He did some of the GFX in some of our demos. And Ajrarn, he, & I were making a game together at one point. I also taught Aragorn some hardscrolling tricks (credited in the scrolltext of his Ventura demo IIRC).
by alien
Wed Jan 06, 2016 1:28 am
Forum: News & Announcements
Topic: "We Were @" final version!
Replies: 6
Views: 4583

Re: "We Were @" final version!

Congratulations on the HD support Leonard!

How did you do it?
by alien
Tue Dec 29, 2015 4:41 am
Forum: Ym rockin'
Topic: Troed's vlc player
Replies: 1
Views: 10545

Troed's vlc player

Troed of Sync made a nice plugin for Mac VLC 2.2 that wraps sc68 to play SNDHs. It doesn't seem to have been mentioned on the forum, so I thought I'd post it.

http://blog.troed.se/2015/10/13/atari-st-chiptune-plugin-for-vlc/
by alien
Sun Dec 27, 2015 3:38 pm
Forum: Coding
Topic: ATARI HDD low level info
Replies: 47
Views: 18163

Re: ATARI HDD low level info

"Scheibenkleister II / Massenspeicher am ST" by Claus Brod and Anton Stepper is a book that has a lot of information about programming the harddrive. But it's in German. ISBN 3-927065-00-5 It does look like quite the rabbit-hole though. (a metaphor for an entry into the unknown, the disori...
by alien
Sun Dec 27, 2015 3:32 am
Forum: Coding
Topic: ATARI HDD low level info
Replies: 47
Views: 18163

Re: ATARI HDD low level info

Mikefulton wrote:None of this is news, but my experience is that there's often a big gap between what's actually necessary to produce a desired result, and what people THINK is necessary.


I'm sorry, I thought you were genuinely interested. I'm quite confident Leonard can code.
by alien
Sun Dec 27, 2015 1:04 am
Forum: Coding
Topic: ATARI HDD low level info
Replies: 47
Views: 18163

Re: ATARI HDD low level info

Demos often use all of RAM. TOS expects part of that RAM to contain its variables. Therefore TOS isn't any use. Also TOS runs its own interrupts that take up too much CPU or occur at inopportune times. Instead of using TOS, demos often use custom floppy loaders. It's not an OS, just a barebones flop...
by alien
Fri Dec 25, 2015 9:36 pm
Forum: 680x0
Topic: STE specific fullscreen issue
Replies: 34
Views: 16569

Re: STE specific fullscreen issue

Perhaps a plan B: use one colour less in the background or foreground so you can set colour 0 to black. It would be less visually disturbing that way.
by alien
Thu Dec 24, 2015 3:46 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 171884

Re: horizontal scrolling on ST

"LINE=PAL at cycle 54" is the decision point where a line will be NTSC (HBL at cycle 508) or PAL (HBL at cycle 512). Changing to 60/50 Hz after this point won't affect the number of cycles in the line. This can be an important point and lead to some problem when removing top border for ex...
by alien
Thu Dec 24, 2015 3:40 pm
Forum: 680x0
Topic: STE specific fullscreen issue
Replies: 34
Views: 16569

Re: STE specific fullscreen issue

@Troed: I think we're just not agreeing on the term preload. 16 cycles = 4 words earlier than the ST. But the ST preloads 4 before starting to display. So that makes 8 for the STe, and 4 for the ST. By preload I just mean: loads the pixel data before starting to display it on the screen. You might m...
by alien
Thu Dec 24, 2015 12:35 am
Forum: 680x0
Topic: STE specific fullscreen issue
Replies: 34
Views: 16569

Re: STE specific fullscreen issue

Glad you figured it out!
by alien
Thu Dec 24, 2015 12:32 am
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 171884

Re: horizontal scrolling on ST

Gee there's a lot more in this thread since I last looked at it...

Go to advanced search