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Thread: Hardware Cursor

  1. #1 Hardware Cursor 
    Forum Freshman
    Join Date
    Apr 2009
    When viewing the options for some computer games I noticed an option for "Hardware Cursor" and enabling that option greatly improved the smoothness of the cursor motion. I tried googling to find out how the Hardware Cursor option works and this is what I found. Tell me if I'm getting this right.

    Normally the cursor is drawn with software. The cursor movements are read in by the CPU which at that point goes into a subroutine to calculate the new position of the cursor and then send both the information about the location of the cursor and how the cursor should look like to the graphics card and eventually onto the screen.

    With the hardware cursor option enabled all data about the cursor movement is rerouted by the CPU straight to the graphics card where there is a chip dedicated to calculating the cursor position and drawing it. I can't figure out however how the graphics card would know how the cursor should look like. Does the software send the cursor images to the graphics card one time and then updates it as needed to change the shape of the cursor?

    Is that how these things work?

    Thanks in advance.

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  3. #2  
    Join Date
    Jan 2008
    A little history first...

    Originally a hardware cursor was a set of latches set to an address somewhere in video ram, this address was fed to one side of a comparator wih the other input coming from the screen address currently being written to the screen device, when the two address's matched a signal was sent to slightly increase the brightness of the screen at that point and thus produce the original cursor. By switching on and off the signal at regular intervals a flashing cursor was produced.

    From your description it looks as though they have merely transferrred this function to the video controller and are doing it in software (but still calling it a hardware cursor).

    Yes, they will need to feed in the cursor image to the video system, there may well be a unique reoutine for this which will allow you to 'point' to a bitmap file that can be loaded by the system.

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