Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!gem.mps.ohio-state.edu!ginosko!usc!ucsd!nosc!logicon.arpa!trantor.harris-atd.com!ringworld!laprade From: laprade@ringworld.harris-atd.com (Ken Laprade) Newsgroups: comp.sys.amiga.tech Subject: Re: OVL line in Amiga 2000 Message-ID: <2559@trantor.harris-atd.com> Date: 18 Aug 89 18:19:06 GMT References: <8908181206.AA07159@jade.berkeley.edu> Sender: news@trantor.harris-atd.com Reply-To: laprade@trantor.harris-atd.com (Ken Laprade) Organization: Advanced Technology Dept., Harris Corp., Melbourne, Fl. Lines: 27 In article <8908181206.AA07159@jade.berkeley.edu> U211344@HNYKUN11.BITNET (Olaf 'Rhialto' Seibert) writes: > ... >This makes me wonder. The 2000 doesn't need a boot rom, does it? The >start of the kickstart ROM has the same structure as the boot rom >in the 1000. (I know; I disassembled it). Does the OVL line maybe >map a PART of the kickstart rom to location zero? Or is there a >boot rom anyway? > ... The 2000 certainly needs a boot ROM (whether it is called 'boot' ROM or 'kickstart' ROM doesn't really matter). It also needs to give the 68000 the location of that ROM via the reset vector at location 0. Any 68000 based machine that wants to have low RAM (for the interrupt vectors) must somehow trick the 68000 into fetching the vectors from ROM until the RAM ones are ready. The Amiga does this with the OVL line controlled by the CIA. A related question: Is the kickstart disk (for 1000's) an exact image of the ROM version? Does it have the exact same startup code (including reset vector) as the 1000 boot PROMs? I.e., can I just blow PROMs from the kickstart disk and install them in the 1000 (with appropriate changes to disable the kickstart RAM)? -- Ken Laprade ARPA: laprade@trantor.harris-atd.com Harris Corporation - GISD UUCP: ...uunet!x102a!trantor!laprade Palm Bay, Florida voice: (407)727-4433