Q. What is the max video resolution ?

A. The number of "standard resolution" pixels in the maximum viewable video window depends on the output mode:

a) in PAL (50Hz) - 368x256 pixels non-interlaced (368x512 interlaced)
b) in NTSC (60Hz) - 368x232 pixels non-interlaced (368x464 interlaced)
c) in VGA (60Hz) - 368x240 pixels

(These figures do not include overscan areas, the hardware can produce a video window outside the viewable area if necessary)

As the PAL/NTSC pixel clock is 8MHz* (as opposed to the more common 7.x MHz) the pixels are slightly (vertically) rectangular. (They are more noticably rectangular in the VGA and NTSC modes)

If compatibility across all video systems is important, 368x232 should be chosen. As well as screen data being missing from the bottom of the screen if full screen PAL mode is chosen with a non-PAL output device, there's a danger that a program will not run properly. (EG: If interrupts are set to occur in the lower part of the frame.)

• A hi-res "filter" can be enabled which doubles the horizontal resolution, but sacrifices colour depth to achieve it (4 bit colour indexes). This only works by doubling the pixels clock, as such it only works in PAL and NTSC mode because the pixel clock in VGA mode is already maxed out at 16MHz. See hi res mode for details.

Q. How do I switch video output modes ?

A. PAL or NTSC is selectable with program code, using a PAL/NTSC port bit (see sys_hw_settings). VGA output mode is selectable with hardware jumper located on the PCB (jumper on for VGA). Interlace and Hi_Res mode are controlled bits 2 and 3 in vreg_ext_vidctrl

Q. Does the VGA jumper override the PAL/NTSC bit ?

A. Yes.

Q. What output standard is used for TV modes?

A. It is RGB and Composite-Sync. You can connect it directly to SCART connector of your TV. Or use an external RGB-->Composite converter.

Q. What is output is used for VGA video output ?

A. It is standard analog VGA. 5 standard VGA wires: analog R,G,B, digital H- and V-sync

Q. Is there any way for program code to obtain current video output mode ?

A. Yes, there is are two flags, bit 5 of sys_hw_flags is set if the VGA jumper is connected, and bit 5 of vreg_read is set if in 60Hz mode.

Q. Can I set my own resolution ?

A. Only via interlacing and/or hi-res mode on non-VGA displays. You can set your own display window size on all systems:

Horizontal window size is set with 16 pixels step, vertical size with 8 pixels step. The smaller window size you set, the bigger border you get. For example, you can set the window size 256x240 pixels, thus you obtain left/right border of 56 pixels. ((368-256)/2)

Q. Is there any reason to use smaller window sizes (e.g. 320x200, 256x240, etc...) ?

A. Only to save video RAM (for double buffer, blitter source area etc), or to have less contention when accessing video memory.

Q. Can I use a TFT VGA monitor with the device ?

A. Yes, but there maybe some uneven pixel interpolation caused by the monitor's scaling matrix (a common issue for TFT panels when working with low resolutions.)