Installing the RTG driver

Overview

Jason Mac Mullan kindly develops and maintains the SAGA RTG Driver to be used with the Digital Video Out of the Vampire boards. The driver is still in a beta stage.


1) Install the required files

1.1) Install the P96 RTG System

  1. Download the free P96 archive.
  2. Use the provided installer and follow the instructions carefully.
    • The original Picasso96.lha archive is hosted here legally, for preservation reasons. Its contents remain unchanged from the original, conforming to the license. You can update LIBS:Picasso96/rtg.library yourself from other sources, for stability improvements.

1.2) Install the SAGA RTG Driver

  1. Download the latest SAGADriver package.
  2. Use the provided installer and follow the instructions carefully.

1.3) Install Universal ModeLine Calculator

  1. Download UMC from Aminet.
  2. Copy the file umc/umc to C:umc.

1.4) Reboot your computer


2) Configure the SAGA monitor

The SAGA Core uses the FastRAM of the Vampire board to display the video on the screen. The driver allows you to configure how much of the FastRAM will be reserved for the Video FrameBuffer. The default is 8MB. This means, after driver initialization, your available FastRAM is ( 128MB - 8MB ) = 120MB. You can configure this behavior by adding a tooltype to the DEVS:Monitors/vampiregfx.info file. This feature allows you to save unused memory by configuring the video memory size that fits your needs. Let's say someone will never use a screen larger than 960x540x24bits, then that person will need only 1.5MB.

You can easily calculate the video memory size using the following formula:

(Width*Height*BytesPerPixel)
where BytesPerPixel is 1 for 8bits, 2 for 15/16bits, 3 for 24bits, and 4 for 32bits.

ToolType syntax:

VideoMemSize=xxxxx
; where xxxx can be bytes, xxxxK (kilobytes), or xxxxM (megabytes).
; K, M are not case-sensitive.

Examples:

VideoMemSize=8M
VideoMemSize=4M
VideoMemSize=600K

Remark:

The SYS:Prefs/Picasso96Mode tool will automatically hide (disable) all the resolutions that need more memory than the memory allocated by the SAGA RTG Driver.


3) Test desired screen modes

  • You can test RTG screen modes from the ScreenMode Preferences of AmigaOS.
  • You should use resolutions and refresh rates that work best with your monitor or TV.
  • We recommend using 1280×720 or 960×540 for the best AmigaOS experience.
  • If you have a Vampire Standalone, make sure you test 720×576@50Hz and 720×480@60Hz, to ensure that your monitor or TV works well with them. The Vampire outputs non-RTG screens using these two screen modes. (The former in PAL mode and the latter in NTSC mode.)

Creating new screen modes

The SAGADriver package already installs some commonly-used screen modes. But if the provided screen modes are not sufficient for your needs, you can create your own:

  1. Open a Shell window (newcli).
  2. Run umc <width> <height> <refresh_rate> --rbt to get the appropriate mode settings.
    • For example, if you want a 720×576@50Hz screen, run umc 720 576 50 --rbt.
    • You can request any mode from 320×200@200Hz up to 1920×1080@28Hz. However, there are some limitations, which you can ensure by reviewing the output of umc:
      • Higher resolutions and refresh rates require higher clock rates.
      • The clock rate should be at least 25MHz, which is the minimum allowed value for Digital Video.
        • Many monitors and TVs are flexible and support clock rates that are even lower than this minimum value.
      • The clock rate must be at most 65MHz, which is the maximum allowed value on Vampire boards.
      • The resolution, the horizontal frequency and the vertical frequency (refresh rate) should be within the specifications of your monitor or TV.
        • Usually, the monitor or TV supports a specific subset of standard refresh rates, like 24/25/30/50/60Hz.
      • The --rbt parameter is strongly recommended, because it will apply a special formula to reduce the blanking time and deliver the same resolution & refresh rate with a lower clock rate. In this way, you can save some bus bandwidth, and also create high resolutions & refresh rates that would otherwise be unreachable due to the upper limit of the clock rate.
      • If your monitor or TV does not work with “rbt” modes, you can try omitting the --rbt parameter. For example, if --rbt slightly reduces the desired horizontal/vertical frequencies, and the reduced values fall slightly below the minimum specifications of your monitor or TV, then you should omit it. Or, if you are creating a low resolution & refresh rate, and --rbt causes the clock rate to fall below the lower limit, then you should omit it. In these cases, even omitting --rbt might be insufficient, and you might need to add the --margin=<percentage> parameter. (For example: --margin=20)
      • You will be able to achieve a refresh rate of 60Hz for all resolutions up to and including 1280×720. If you want to create a resolution higher than that, then, a refresh rate of 50Hz (or above) will exceed the upper limit of the clock rate, even with the help of the --rbt parameter. You will be forced to reduce the refresh rate down from 50Hz. Here are the maximum refresh rates you can achieve for a couple of example resolutions:
        • 1600×900: ≤40Hz
        • 1920×1080: ≤28Hz
  3. Run SYS:Prefs/Picasso96Mode.
  4. Create a new resolution.
  5. Enter the width and height.
  6. Create a new mode.
  7. From the output of umc, take the values under Picasso96Mode values and apply them to the settings of the newly-created mode.
  8. Select the color depth you want.
    • Chunky (256 Colors) is 8 bits/pixel.
    • HiColor is 16 bits/pixel.
    • TrueColor is 24 bits/pixel.
    • TrueColor & Alpha is 32 bits/pixel.
  9. You can create multiple modes for the same resolution, each with a different color depth. Just make sure that the mode settings come from the output of umc.
  10. Test all of your newly-created modes before saving.
    • If you have followed the instructions carefully, but your mode is still not working even though it seems like it should, then you can modify the mode settings (such as the clock rate) manually, in order to obtain a mode that works well with your monitor or TV.
  11. After saving and rebooting, the new screen modes will be available in the ScreenMode Preferences of AmigaOS.
→ If you have a Vampire accelerator board connected to a classic Amiga, the line size must be aligned with the memory burst size, which is 32 bytes. In other words, the horizontal resolution multiplied by the color depth (in bytes) must be a multiple of 32.

→ If you have a Vampire Standalone, the line size is independent of the memory burst, but it must still be aligned to 8 bytes. In other words, the horizontal resolution multiplied by the color depth (in bytes) must be a multiple of 8.


Additional information


Roadmap

  1. Need deeper implementation of P96 subsystem, currently based on AROS.

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Last modified: le 2019/11/29 06:14