Centris Quadra 800 Video

Date: Tue, 30 Mar 93 09:03:17 EST From: vita@sunny.dab.ge.com (Mark Vita) Subject: Centris / Quadra 800 video report Here is a very informative report on the built-in video capabilities of the Apple's new Centris 610/650 and Quadra 800 machines. The report was written by Dale Adams, the designer of the video hardware on those machines. It includes a complete description of the available resolutions and bit depths, the types of monitors supported, and the video connector pinouts (including the sense pin configurations necessary to enable the various display types). Mark Vita vita@sunny.dab.ge.com GE Simulation and Control Systems Daytona Beach, FL --------------------------------- cut here ------------------------------------- Built-In Video on the Macintosh Centris 610/650 and Quadra 800 There will probably be a number of questions which arise concerning the built-in video capabilities of the new Macintosh Centris 610 and 650, and the Quadra 800. In anticipation of these questions, here is an article (similar to that which I posted for the earlier Quadra machines) which provides an description of these video capabilities. This article discusses a few general video topics, details how to wire the video connector sense pins to access all the supported video modes of these machines, and describes the memory configurations necessary to support each of the video modes at specific pixel depths. (I am the designer of the video hardware for the Quadra 700/900/950/800 and the Centris 610/650, you can be reasonably sure this information is accurate.) General Video Design Philosophy -------------------------------------- The video hardware design of the Centris 610/650 and the Quadra 800 is highly derivative from the earlier Quadra machines. However, one of the main goals of these CPUs (and perhaps the #1 goal) was to reduce the cost of the machines relative to the Quadra 700 and 950, while still providing the same (or better!) performance. While it was not possible to significantly reduce cost while maintaining the exact feature set of the earlier Quadras, most of the Quadra video features were carried through to the Centris 610/650 and Quadra 800. The main exceptions are support for Apple convolution (flicker reduction) for NTSC and PAL, and support for 24 bits per pixel (bpp). The video hardware for all three CPUs, the Centris 610 (C610), Centris 650 (C650) and Quadra 800 (Q800), is virtually identical. The only exception is that the C610 only requires 100 ns VRAM, while the C650 and Q800 require 80 ns VRAM. The maximum supported pixel depth is 16 bpp. This is not a matter of the amount of VRAM in the machine - it is a hardware limitation The RAM/DAC used by all three machines simply does not include the hardware required to do 24 bpp on any display. The same is true for the lack of support for Apple convolution - the hardware necessary to do this is not present in the machine. 24 bpp support wa…