Re: [hatari-devel] looking for someone with a mono monitor

[Carsten Jacobi <carsten@xxxxxxxxxxxxxxxxxxx>]

Hello there,

sorry for the late answer, I just got hold off this post last month. I 
played around with ray-beam synchronized routines in monochrome 
beginning of the 90s since everybody was fixed on colour mode those days.
The demo should open the right border and should also - in some respect 
- open the left border (but here I just saw a "gain" of maybe 4 to 8 
pixels).
You should also see a picture wobbling up and down and the funniest 
feature should be seeing the "colour" grey (and I really mean grey, no 
interlace!) on an SM-124 monitor.
I found switch spots that made an STF (indeed I played with this on my 
1040STF) skip lines (that's why scrolling the full picture without 
wasting mem is possible). The left border then does not "open" the same 
way it does in colour mode. Instead, the line is "shifted" 4 to 8 pixels 
to the left end also "ends earlier". However, the right border "opens" 
and that to a really long extend ... the grey part will remain my 
secret, demo programmers should not disclose to much to keep the 
"community" challenged >8-E3= (if you really want to know, you already 
have the source ... the only drawback is that the comments may be in 
"native language")

I was even able to draw graphics in the lower border ... but only on 
"some models". I switched to external synchronization for some cycles 
and then back to internal synchronization. That made the MMU begin a 
completely new frame (starting with the video-counter at the new-VBL 
address again even though the frame didn't end yet!) and so even 
vertical screen splitting was possible. On monochrome, the "newly begun" 
frame then could also extend into the lower border, so the actual 
"opening" of the lower border as in colour mode didn't take place ... I 
never found a method how to do that in monochrome.
I wanted to know how "compatible" screen splitting would be (one example 
is that on the STE in contrast to the STF you had to stay in monochrome 
mode for 20 and not just for 16 cycles to open the left border, so there 
are demos that open the left border but are not "STE"-compatible) to 
other STs, so I started my prototype on 7 different STs on one demo 
party ... and only 2 of them started a new frame after the 
External/Internal synch switch, the others just showed "black" as long 
as the ST ran with external synchronisation. One striking fact was that 
those 2 STs were my 1040ST and the other was a 520ST with a "13 line 
Glue-Chip", my was a "29 line Glue-Chip" (that measure refers to the 
size of the upper border in colour 50 Hertz).
Another problem is also that in monochrome you don't have the means to 
"switch into some different mode" that is also monochrome as in colour, 
where you can switch between 50 and 60 Hertz and both modes operate on 
the colour monitor. This is especially a nuisance when you open the 
right border for which you have to switch as the ray beam draws pixels 
on your screen. So, you just see a black gap on the screen during that 
very period, where your ST runs in colour screen mode as you watch your 
monochrome mode demo. The other nuisance was, that the spot where you 
have to open the right border in monochrome depended on moon wetness, 
weather situation, whatsoever .... it was different any time I turned on 
my ST. So I had to "extend" the time I switched to colour mode to make 
sure the "critical spot" was within that time, hence I had to stay in 
colour mode for more than 24 cycles (would have to look into the source 
to see for how long).
I wanted to download the .mp4 movie posted here since I myself don't 
know how my screen whould look like on a Mega STE, I tried it on a TT 
last year on an exhibition. Well, of course it didn't work in full 
extend on the TT, at least I could see the picture scroll up and down. 
The .mp4 movie seems to be gone again, sad (I was just curious).

It was a surprise for me to see, that 20 years after I wrote this people 
still tried to run my screen.

Regards,

Starbug

On Mon, 18 Aug 2014 Nicolas Pomarède wrote:
> Yes, do a small video from the start of the program before you start it from
> the gem (to be able to see which borders are changing) and upload it
> anywhere (dropbox, dl.free.fr, ...) ; I think it removes bottom border or
> something like that.
>
>
> I don't need great HD quality, just a video with a camera to see what's on
> screen should be enough
>
>
> In your case, the mega ste should be put in STE compatible mode (8 Mhz
> instead of 16 for cpu), but I don't know if this demo works on STE or only
> STF.