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The difference between 50 and 60 Hertz color mode :
In 50 Hz mode with using the Composite Sync signal You have 236 Bytes
per scan line.
210 Bytes are visible .
The other 20 Bytes aren't visible because of horizontal flyback
blanking ( the BLANK signal of the GLUE is doing his job during this
time period !)
Well, 236 Bytes can be divided by 4 , this is what GEM needs.
So 50 Hertz GEM SHELL installation is no problem.
In this moment our Overscan.PRG (version 1.6) runs the GEM SHELL only in
50 and 71 Hz.
In 60 Hertz mode You have 234 Bytes per scan line.
This is only dividable by 2!
So it might be that we will get GEM only to work in Mid-Res-mode in 60
Hz, but a special written Cyberpaint could also handle 60 Hertz, if the
color palettes are adapted the right way in Lowres.
There would have to be 2 different versions of Cyberpaint like Spectrum
512, because in 50 Hz there are 512 clock cycles and in 60 Hz there are
508 Clock cycles per scan line.
In 60 Hz there are also only 238 visible scan lines instead of 284 of the
50 Hz mode.
----------------
Aufl”sung Breite H”he BytesProZeile Theoretische Breite Offset
---------------------------------------------------------------------
Niedrig 400 280 236 464 252
Mittel 832 280 236 928 248
Hoch 672 480 100 800 9800
Die Breite ,H”he und Offset sind jeweils Monitor abh„ngig und mssen
eingestellt werden. Die bisher erreichten MaximalWerte auf blichen
Monitoren mit geringer Modifikation (Verschieben und Verkleinern des
Monitorbildes mit den vorhandenen Monitorreglern) :
Fernseher : Niedrig 416x280, Mittel 848x280
SC1224 : Niedrig 400x280, Mittel 832x280
SM124 : 688x480
NEC-Multisync : Niedrig 432x280, Mittel 864x280, Hoch 732x480
Steven Seagal wrote:Steem_lace_09.png
This is the circuit as documented.
Maybe the experts here can deduce what it's doing exactly, if it's detailed enough?
Notice the switch (ACIA RTS) isn't emulated in Steem because hardware overscan is emulated as a new ST model, you don't switch it off.
Steven Seagal wrote:This too was requested in another thread, support for hardware hacks that intercept the 'DE' line between the GLUE and the Shifter.
Hence only possible on the STF/Mega ST.
Little teaser pictures but it's just a dirty hack (how appropriate) in Steem for the moment.
What is "Off"?
Any info you have is welcome.
Basic use (in addition to the hyp file).
Does it work at 60hz?
Is the picture shifted on the left, the right?
How many lines are displayed? Where does the overscan start? Sooner than in fullscreen demos (line -29)?
In low res, the overscan lines are 236 byte long. In high res? (not tried yet)
A potential problem is that adapting Steem display sizes would be a pain.
Greenious wrote:The original overscan-archive contains a lot more technical details about the actual workings of overscan, exact screen sizes and such.
And of course, using the unused RTS pin on the ACIA to make everything controllable by software so that you automatically can disable overscan when you start software that's incompatible, etc.
Greenious wrote:Off is offset between end of line and next line. There are bytes read/counted by mmu/shifter that never makes it to the screen.
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Fernseher : Niedrig 416x280, Mittel 848x280
SC1224 : Niedrig 400x280, Mittel 832x280
SM124 : 688x480
NEC-Multisync : Niedrig 432x280, Mittel 864x280, Hoch 732x480
troed wrote:Unfortunately I seem to not have researched where VBLANK ends so can't say what the maximum numbers of lines isI have a vague memory of having read something that would lead me to believe it would be line 26. If so (a big if) it would be 308-26 = 282 lines. But, as I said, it would need testing.
(And if anyone's interested, test by being in mono over cycle 502 on line 26 and see if the screen is kept blank, i.e, V never signals which means DE never signals)
/Troed
1st1 wrote:Very interesting! Are your modifications compatible with the AutoSwitchOverscan-driver?
Steven Seagal wrote:1st1 wrote:Very interesting! Are your modifications compatible with the AutoSwitchOverscan-driver?
I can't find this driver, if you have a link to it (and maybe some doc) I will test.
troed wrote:Theoretical maximum mono horisontal resolution should be (184-4)*4 = 720
troed wrote:troed wrote:Theoretical maximum mono horisontal resolution should be (184-4)*4 = 720
Right, that was wrong. I was counting from regular H = TRUE. With DE constantly on it might be (184-(212-224))*4 instead, that is, 784. This is assuming there's no BLANK = FALSE done later than HSYNC = FALSE (I don't know of one).
Mono statemachine
4: IF(71) H = TRUE
164: IF(71) H = FALSE
184: IF(71) BLANK = TRUE
188: IF(71) HSYNC = TRUE
212: IF(71) HSYNC = FALSE, BLANK = FALSE, hSYNC_COUNTER reset
troed wrote:Mono statemachine
4: IF(71) H = TRUE
164: IF(71) H = FALSE
184: IF(71) BLANK = TRUE
188: IF(71) HSYNC = TRUE
212: IF(71) HSYNC = FALSE, BLANK = FALSE, hSYNC_COUNTER reset
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