Screen-rolling on Turrican on my 6128

[MugUK]

My 6128 troubles are almost over and I finally (!) got to play some games this afternoon.

However, I noticed a real oddity in Turrican.  I'm assuming it's using some advanced trickery as it causes the monitor screen to roll around constantly ..making it unplayable. 

I'll get a picture of the effect if this is not a 'standard' problem.  When connecting the 6128 to the LCD TV, the display is black & white for all games but in Turrican, it disappears off to the left of the screen

Is it a known issue with this game?

[beaker]

Hey MugUK, glad to hear you've sorted out most of your problems. Sounds like you have the same problem as Protek had recently RGB switching.
Turrican should work - I've got the cable from Retro Computer Shack and it looks fine on my plasma as per attachment. Sorry I can't be of anymore help.

[Gryzor]

Oh, finally you got it rolling. Great weekend, then!

[MugUK]

Oh, finally you got it rolling. Great weekend, then!

Screen-rolling as in, to use an Atari ST description, trying to play a game at 60hz when your TV can only handle 50Hz?

I'll upload a picture or two later on.

[beaker]

Oh, finally you got it rolling. Great weekend, then!

ROTFL - that made my weekend! you definitely have a British dry sense of humour!!! 

[MugUK]

First post is covering what happens with the Retro Computer Shack SCART TV kit connected to my 19" LCD TV

[MugUK]

And this is the result of using the game on my stock Amstrad colour monitor

Is my monitor knackered in some way - it's the only game I've found so far which does this hence me thinking it's some magic coding being done a la bottom-border removal on the ST etc.

[eliot]

Turrican uses a split-screen ingame.
Maybe you have to set the V-Hold of your Amstrad monitor (behind) at a decent set-up...

[Gryzor]

@eliot: you beat me to that, was gonna ask that...  If that's not the case, could it be a CRTC issue?


@beaker: why thank you kind sir, I take this as a great compliment. And I didn't even have a beer!

[MugUK]

Turrican uses a split-screen ingame.
Maybe you have to set the V-Hold of your Amstrad monitor (behind) at a decent set-up...

D'oh - the Muppet Award for Not Knowing About the V-Hold Dial goes to ..... me!   

Cheers Elliot! All working now ;-)

[Grim]

Interesting. The frame-rate during the game is around 52.8Hz instead of the usual ~50Hz (ie. 296 lines instead of 312). It seems the programmer had some troubles with CRTC register 4 for his ingame splitscreen. (and for all these years, I though that game coders were more serious and careful than demo coders with their sloppy tricks... looks like I was wrong :)

On a CTM64x, adjusting the V-Hold will do. To run on modern TV stuff however, that game should be patched to produce a standard 50Hz framerate.

[fano]

Seems you're right , the split screens are #14 and #0F values for R4.I am trying to isolate code to fix it.

Can I ?

Spoiler: ShowHide

If you break any of these rules, I will laught out loud and throw shit at you!
(I'm still not kidding! You've been warned.

[fano]

I took a look quicky.
The code is located at #CF4B with ld DE,#0414 , you can replace with ld DE,#0416.The string to search on disk is 11,14,04,ED,51,04,ED,59 , replace #14 by #16.
The problem is the only dump i know uses Hexagon protection and it seems to have checksum and i do not know how it works, if someone got another dump or know how to cheat Hexagon checksum protection.

[Grim]

According to the routines at &CF4B and &CF68, the splitscreen uses &14 and &0F for R4. Replacing that &14 with a &16 (poke &CF4C,&16) and we're good, (&14+1 + &0F+1)*8 = 312.

On the original DSKs, the routine can be found at offset &C5C8 of side A. But when I change the &14 with a &16, the game stops working. The game's protection must be doing some checksum somewhere. Frak!

Anyway, the guy wrote that code in 90, probably in a hurry to finish on time, so a gentle tap on the back of his head will be enough imo :)

EDIT1: Ah, you posted sooner than me! :)

EDIT2: Well, I did a (crude :) loader for the original game to fix the splitscreen. See the attachment.

[Executioner]

Anyway, the guy wrote that code in 90, probably in a hurry to finish on time, so a gentle tap on the back of his head will be enough imo

In other words it was written back when no-one but a few demo coders knew enough about the 6845 to know how to calculate what values to put in the registers to do a split screen, and simply used experimentation to find some values that worked on their own monitor.

[TFM]

Ah no, there were split screen games way before 1990.
Game coders had that before demo makers.

[MugUK]

I'm just glad that my own noobishness got a game re-patched in the year 2012

[SyX]

Well, the spanish version doesn't use any protection and is only a one bit fix

Druid 2 is another case of bad split, the framerate goes between 48 and 49 Hz, i have it in my todo list, but feel free to fix it, add the screen of this post and i will cross out of my list 

[TotO]

Now, need to translate it!!! 

[SyX]

to spanish??? xDDDD

[TotO]

Sure! 

[Executioner]

Ah no, there were split screen games way before 1990.
Game coders had that before demo makers.

Yes, there were a few (very few), and they were very basic split screens, and I had problems with VSync on a number of them (eg. The Living Daylights). The only game I can remember which (may have) got it spot on was Mission Genocide.

[TFM]

That's right, I remember some problems too. Had another CRTC later, then it worked better.

[MugUK]

Playing some other games when I got in this evening and the fix for Turrican has caused Roland on the Ropes to flicker slightly with the status bar at the bottom of the screen also flickering in the top part of the screen.

No massive problem as I prefer Turrican

[TFM]

You could adjust it in a way that it works for both :-) Else.... you can use the Turrican - SyX Version