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Screenshots - SeBra

SeBra atari screenshot

Information - SeBra

GenreHardware - Emulation / OS FixingYear1995
LanguageMachine LanguagePublisherST Format
Developer[n/a]DistributorFuture Publishing
ControlsMouseCountryUnited Kingdom
Box / InstructionsEnglishSoftwareEnglish

Persson, Patrik

LicensePD / Freeware / Shareware
SerialST TypeST, STe / 0.5MB
ResolutionLow / MediumNumber of Disks1 / Double-Sided / HD Installable
Dumpdownload atari SeBra Download / MSAMIDI

Additional Comments - SeBra

Other version with the same title:

ST Format (version 1.32) ().

Instructions - SeBra

                              SEBRA version 1.33

                   The High-Res Monochrome Monitor Emulator

                           Patrik Persson 1992-1994

          The ST's graphics are great. Lots of colour and fast animations - 
     but there is one problem: you can't use the high resolution mode on a 
     colour monitor or a TV set. Of course you can buy a second high 
     resolution monitor as well, but it still costs about œ100. A Multisync 
     monitor capable of displaying all three ST resolutions costs about four 
     or five times as much. Atari never mentioned this problem in their 

          So I wrote a program called SeBra which allows the previously 
     impossible: to run the high resolution (640x400) mode on a colour 
     monitor/TV set! It is intended for use with all ST/STe/Mega computers.

          It doesn't actually send the monochrome signal to the colour monitor 
     (it can't cope with the 71.25Hz vsync frequency) but instead uses a 
     number of different algorithms to convert the 640x400 picture to a medium 
     resolution 640x200 picture.

          You may wonder why I called it SeBra? (Oh yes, you do...) Well, the 
     word sebra is (you guessed it) the Swedish spelling of the word zebra 
     (black & white) but can also be split into the two words 'se' and 'bra', 
     meaning 'see' and 'well' respectively. Interesting, isn't it?

          I have tried some other other small utilities that try to do the 
     same thing as SeBra (MONOEMU5, GFA-MONO etc) but I'm happy to tell you 
     that SeBra is faster, more compatible (they both have problems with the 
     STE), takes advantage of a blitter chip (if you have one) and has lots of 
     other nice options.

          You install SeBra by putting it in the AUTO folder of your boot disk 
     or hard disk. Upon booting a message is displayed and SeBra allows you to 
     skip its installation by pressing the Esc key. Pressing any other key 
     activates SeBra.

          Your ST now thinks that it's equipped with a high resolution 
     monochrome monitor, but that's not all: in some respects, it's even 
     better. By pressing Control, Alternate and another key, you can make 
     SeBra do lots of nice tricks.

                          THE THREE DIFFERENT MODES

          To begin with, Control+Alternate and the three keys "(", ")" and "/" 
     on the numeric keypad allows you to switch between three different 
     display modes. The first (Ctrl-Alt-"(") is the 'shaded' mode. This 
     converts the 640x400 monochrome screen into a 640x200 screen in three 
     colours. The 'shaded' mode is the mode that gives the best overall view, 
     but it is also the slowest. It is similar to the display produced by 
     other 'Mono Emulators'.

          The second mode (Ctrl-Alt-")") is the 'fast' mode. It was invented 
     to give the same speed as the 'magnified' mode (see below) and show the 
     whole screen at once. It is very simple: it converts the 640x400 screen 
     to a 640x200 screen by skipping every other scan line.

          The third mode (Ctrl-Alt-"/") is the 'magnified' mode. It displays 
     200 of the 400 scan lines. By moving the mouse you can scroll vertically. 
     This mode is the fastest and clearest of the three.

                              THE SPEED CONTROL

          The process of converting the high resolution screen to a medium one 
     takes some effort from the processor (although a blitter chip can reduce 
     the load). The more processor time you for the emulation, the less can be 
     used for the actual program. If you use less processor time for the 
     emulation, the display gets jerkier (especially in the 'magnified' mode). 
     SeBra allows you to choose the amount of processor time to use for the 
     emulation. Press Control, Alternate and one of the keys "1", "2" or "3" 
     on the numeric keypad to select speed. "1" gives a jerky screen, but the 
     processor is not not slowed down very much. "2" is normal and gives a 
     good screen update but a slight speed reduction. "3" gives a very solid 
     display, but the speed reduction is significant.

          I have included an option to improve the mouse movement by updating 
     the mouse pointer whenever it is moved. This means that the slow speed 
     mode often can be easier to use, and also improves the normal speed mode. 
     It can be switched on with Control, Alternate and the "+" key on the 
     numeric keypad and off with Ctrl-Alt-"-". The only drawback is that it 
     needs about 2-3% of total processor time if the mouse is moved about a 
     lot. You wouldn't have noticed if I didn't tell you!

          Another thing that affects computing speed is the vertical 
     synchronisation frequency. In Europe this is normally 50Hz but can be 
     changed to 60Hz (USA). Most programs don't mind, but some TV sets and 
     possibly some monitor can't cope. Anyway, the 60Hz display is more 
     pleasant to the eyes. It also increases emulation speed (and reduces 
     processing speed) slightly. Press Control, Alternate and the "*" key on 
     the numeric keypad to toggle vertical synchronisation frequency.

          In order to keep loading and saving as fast as possible, the 
     emulation speed is automatically reduced to a minimum when a disk drive 
     is working. The speed is then restored to normal when the drive stops.

                                COLOUR CONTROL

          Even if SeBra emulates a mono monitor, you can use colour! Press 
     Control, Alternate and Enter to choose between four different colour 
     schemes (try that on a mono monitor) and Control, Alternate and "0" on 
     the numeric keypad to invert the screen.

                                KEYBOARD RESET

          When I wrote SeBra I included an option to reset the computer from 
     the keyboard (like in TOS 1.04 and later). Press Control, Alternate and 
     Delete to reset. If you hold down the right Shift key as well, memory is 
     rechecked too.

                                BLITTER USAGE

          If you are lucky enough to have a blitter chip in your machine, 
     SeBra can use it. If you turn the blitter OFF in the Desktop menus, this 
     usually means that the operating system leaves the blitter passive (what 
     a waste). SeBra detects this and takes control. So, to make SeBra use the 
     blitter, you first have to tell the operating system to leave it alone by 
     deselecting the blitter in the Desktop menus (or the XCONTROL Control 
     Panel, or any program that has a blitter option).

                               DEFAULT SETTINGS

          Once you have discovered you favourite settings, it would be very 
     annoying if you had to select them on every boot-up. Because of this I 
     have included a menu with which you can select the settings you want and 
     save them. Simply double-click on the SEBRA.PRG file from the Desktop, 
     make your selections in the dialog box and click on SAVE. Your settings 
     will be saved in the program file itself. If you are already running 
     SeBra when you start the menu, you will see the selections take effect as 
     you click the buttons.

          This menu contains an option labelled 'Install automatically'. If 
     you activate this option (click in the little box and a check mark 
     appears) SeBra won't wait for a keypress when you run it from the AUTO 
     folder, but start automatically.

          Please note that while the menu is running, the SeBra keyboard 
     controls are disabled to make sure that all information in the menu is up 
     to date.


          SeBra is compatible with most programs that require a monochrome 
     monitor, such as Calamus, Calamus Outline Art, Calamus Font Editor, CuBase, Creator, 
     DynaCadd, Quick ST 2 & 3 and Signum!2. In general, run most GEM-
     based programs run well, but games (which don't use TOS) usually don't 
     run. Of the programs I have tested only Flight Simulator II and TurboAss 
     (a brilliant German assembler) have refused to run correctly. This isn't 
     too much of a problem since they both run perfectly in colour...

          Many other programs that work in both colour and mono modes work 
     with SeBra. This means that you (for instance) can use HyperPaint to edit 
     monochrome images (.PC3, .PI3 & .IMG).

          It works with all versions of TOS that I have tested it on (1.02, 
     1.04, 1.62, 2.06). My guess is that it works on other versions too. I 
     have been informed that it works with a 16MHz processor and cache. However,
     computers with 68030 computers (TT, Falcon and various accelerators) don't
     like SeBra. But I guess that anybody with enough money for such an
     accelerator can afford a real monochrome monitor...

          Previous versions have contained a slight bug that made SeBra go 
     berserk with 4 meg machines in the 'magnified' mode. Other peculiar 
     things also happened (not only to 4 meg machines). I HOPE it will work 
     better now. Still, I only have a 2 meg STE myself, so don't know for 
     sure. But I think I've found the bug this time.

     Compatibility summary:

     * Most 'serious' applications work.
     * Most games don't work.
     * Most (probably all) TOS versions work.
     * Some accelerators (68000-based) and such things _probably_ work.

          SeBra is in the Public Domain. This means that you can make as many 
     copies as you like and give to your friends at no cost. All financial 
     donations will be gratefully accepted, though...   8-)

          If you find any bugs or have some idea of how to improve SeBra, 
     please drop me a letter. If it concerns bugs, please try to enclose the 
     following information:

     * A detailed description of the situation in which the error occured.

     * What computer (ST/STE/MegaST/MegaSTE etc) you were using, TOS version, 
       memory size, peripherals, other programs in memory etc.

          OK, that's what I wanted to say. I hope you find a use for SeBra and 
     maybe don't have to rush out and buy a new monitor. Enjoy!

                                                       Patrik Persson
                                                       K„mn„rsv„gen 2:184
                                                       S-226 45 Lund

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