Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!mintaka!bloom-beacon!eru!hagbard!sunic!mcsun!hp4nl!cbmnlux!ecl001!ajbrouw From: ajbrouw@ecl001.UUCP (Albert-Jan Brouwer) Newsgroups: comp.sys.amiga.hardware Subject: Breaking through the chip-bus barrier? Message-ID: Date: 18 May 91 16:00:46 GMT Organization: Pelt Computers Lines: 43 There are two more or less fundamental limitations that are holding back our beloved Amiga platform from entering the the 12/24 bit graphics era. First of all the system software is "hard-wired" to the custom chip set. Making the graphics.library device independant will take atleast another couple of years, if at all possible. Ofcourse in due time there will be libraries that support the various add-in graphics boards, but this implies that applications will have to be customized to make use of these. So if upgraded graphics are going to be transparent to applications, and arrive somewhere in the foreseeable future, there HAS to be backwards compatibity with the old chipset. That's were the second problem comes into play; limited chip bus bandwidth. What I want to propose here is a possible way around this problem; Imagine a new Denise (graphics chip) that would snoop the chip bus and maintain a mirror copy of the entire chip memory range. F.e. a small board that plugs into the Denise socket and sport the new Denise and 2MB DRAM. All writes to chip memory would get copied into the mirror chip memory. The new Denise could then fetch all bitplane data from this mirror memory without taxing the chip bus. So this Denise could theoretically display upto 12 bitplanes in hires. More wouldn't do any good because we'd still be stuck with the 4 bit RGB DACs. So here we have a backwards compatible graphics engine. It works with the old custom chips, blitter, agnus..., it can be added to any Amiga, it is supported by the system software with only minor extensions meeded to make use of the additional bitplanes/colours. Sounds too good to be true eh? Probably is. Hope = Pain. Will someone torpedo this please.... -- Albert-Jan Brouwer "Pro is to con as progress is to Congress." Pelt Computers OudeDelft 121, 2611 BE Delft, The Netherlands Tel: +31 15 143824 FAX +31 15 146916 UUCP hp4nl!cbmnlux!ecl001!ajbrouw