History of Viewfinder revealedBy Chris Williams. Published: 14th Nov 2005, 07:16:47 | Permalink | Printable
Plus schematicsThe story behind the development of the Viewfinder, the kit that interfaces an AGP graphics card to the Acorn podule bus, has been revealed online by developer John Kortink. According to the guide, the expansion card uses an Altera programmable chip to act as the glue between the two buses and to perform the colour byte swapping for the RiscPC's BGR format.
The driver software however is the most complex component, as John needed to control the AGP card without any help from the operating system or BIOS, and with limited documentation from ATI. He also had to write an x86 emulator so that the ROMs on the AGP cards could be executed. This was before extra features such as dual head capability and graphics acceleration were added.
The Viewfinder card supports the ATI Rage Pro, Rage 128 and Radeon cards, although it is now no longer available for general sale. Many users regard the Viewfinder as a significant upgrade for the RiscPC.
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