Search found 85 matches

by alien
Mon Oct 17, 2016 1:27 am
Forum: Coding
Topic: Quiz of the week: Single cycle accuracy code.
Replies: 18
Views: 3405

Re: Quiz of the week: Single cycle accuracy code.

Don't think there is any way. The Video Pointer at MMU is just a counter. The only other function besides incrementing is that Vsync edge provokes the higher bits to be reloaded from Vbase and the lower bits cleared. So only possible way seems to be to provoke a Vsync edge ... Interesting. We'd nee...
by alien
Sun Oct 16, 2016 6:07 pm
Forum: Coding
Topic: Quiz of the week: Single cycle accuracy code.
Replies: 18
Views: 3405

Re: Quiz of the week: Single cycle accuracy code.

For some reason, when you asked this question, it brought to mind that I always wondered whether there might be a way to change the video fetch address mid-screen. I tried to find a means in software, but never succeeded. That's something you could check when you decap/reverse-engineer the MMU. If t...
by alien
Thu Aug 18, 2016 3:01 pm
Forum: Hardware
Topic: MMU schematics WIP
Replies: 48
Views: 5997

Re: MMU schematics WIP

Btw, this is one of the problems of using a delay chain. It is variable and not completely reliable. The delay would depend on the board temperature. I wonder if this is one of the reasons of the Shifter weird issues observed depending on the warming (wake substates, as Troed call them). Might be. ...
by alien
Sun Jul 17, 2016 3:53 am
Forum: Coding
Topic: ST Chipset decap
Replies: 84
Views: 17064

Re: ST Chipset decap

Hi ijor, I'm curious whether you've had any chance to learn anything new on this topic since your last update.
by alien
Sun Jul 17, 2016 3:45 am
Forum: News & Announcements
Topic: *** R-TYPE DELUXE SOURCE CODE ***
Replies: 27
Views: 8888

Re: *** R-TYPE DELUXE SOURCE CODE ***

Thanks Bod/Stax, even though you can't read this.
by alien
Mon May 30, 2016 12:40 am
Forum: Hardware
Topic: Resourced TOS Rom
Replies: 47
Views: 6821

Re: Resourced TOS Rom

It makes sense they only got EmuTos working for monochrome mode: the Amiga can't do the type of bitplane interleaving the Atari ST uses, but there's only one bitplane in high-rez. Troed is right. Most games turn off the OS since TOS was notoriously slow. I remember using a "SoftBlitter" wh...
by alien
Mon May 30, 2016 12:03 am
Forum: Coding
Topic: ST Chipset decap
Replies: 84
Views: 17064

Re: ST Chipset decap

I may be misremembering, but I also think it didn't always work, whereas the the above code did force the Shifter to reset as I wanted reliably. Perhaps RESET only clears the IR registers at certain points? You are (partially) right! Yes, hardware reset might not perform actually a clean Shifter re...
by alien
Fri May 27, 2016 8:00 pm
Forum: Coding
Topic: ST Chipset decap
Replies: 84
Views: 17064

Re: ST Chipset decap

Ah, not exactly switches, but whole frames at each rez. I missed that. But if you can spend so much time, then it might be better to execute the RESET instruction. That is guaranteed to work. Of course, it is much more invasive as will affect things that you might prefer to avoid. I also had some &...
by alien
Fri May 27, 2016 4:09 am
Forum: Coding
Topic: ST Chipset decap
Replies: 84
Views: 17064

Re: ST Chipset decap

FWIW, here is the shifter reset code from my article:

reset_shifter:
move.l #$VBL_routine, $70.w
moveq #5,d0
loop:
move.b #1, $ffff8260.w
stop #$2300
clr.b $ffff8260.w
stop #$2300
dbra d0, loop
rts

VBL_routine:
rte
by alien
Wed May 25, 2016 5:31 pm
Forum: Demos - General
Topic: Atari Demoscene
Replies: 34
Views: 14081

Re: Atari Demoscene

Askja wrote:Hi all,

After some months of work, I just finished my giant picture with all the Atari Demoscene!

Enjoy!! :cheers:

http://undead-factory.fr/demoscene/index.html

Image


Very nice!
by alien
Sat May 14, 2016 9:36 pm
Forum: Demos - General
Topic: Now on Kickstarter: The Atari ST Anthology book volume 1
Replies: 20
Views: 11637

Re: Now on Kickstarter: The Atari ST Anthology book volume 1

Ok, Ich könnte vielleicht mit dem zweiten Teil helfen... ich könnte zB eine Verbindung herstellen mit den Franzosen, mit denen ich noch Kontakte habe. Welche Produkte populär waren, hat meiner Meinung nach mehr damit zu tun, in welchem Land man in den 90ern lebte. Hannover ist nicht in der Nähe von ...
by alien
Wed May 11, 2016 1:26 am
Forum: Demos - General
Topic: Now on Kickstarter: The Atari ST Anthology book volume 1
Replies: 20
Views: 11637

Re: Now on Kickstarter: The Atari ST Anthology book volume 1

Man sollte vielleicht nicht die Franzosen vergessen... Ziggy, Mcoder, Algernon: die erste schnelle 3D... ST-CNX: 4bit hardscroll, 6301 Programmierung, der erste MOD player auf ST das Ich kenne und der Schnellsten auf den Atari ST. Overlanders, Legacy, Oxygene, Dune, und so weiter, haben sehr schöne ...
by alien
Wed May 11, 2016 1:09 am
Forum: Coding
Topic: ATARI HDD low level info
Replies: 47
Views: 11334

Re: ATARI HDD low level info

As far as I know, the reason for using our own FDC routines instead of TOS was just that it made it much more practical to write fast loaders that can also do stable animation on the disk. The fact that you got more memory was more of a bonus :) Depended on the demo... Let's do the Twist Again, wou...
by alien
Wed May 11, 2016 1:04 am
Forum: Coding
Topic: ST Chipset decap
Replies: 84
Views: 17064

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: 84
Views: 17064

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: 84
Views: 17064

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: 84
Views: 17064

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: 83
Views: 16716

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: 83
Views: 16716

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: 13329

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: 7060

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: 13329

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: 13329

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: 7060

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: 13329

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...

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