Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!celia!neil From: neil@celia.UUCP (Neil Richmond) Newsgroups: comp.sys.amiga.hardware Subject: Re: Question about the difference between A3000-16/50 and A3000-25/50 Keywords: A3000 speed Message-ID: <1014@celia.UUCP> Date: 7 May 91 17:33:55 GMT References: <116684@tut.cis.ohio-state.edu> <21306@cbmvax.commodore.com> Reply-To: celia!neil@usc.edu (Neil Richmond) Organization: Rhythm & Hues, Inc., Hollywood Lines: 31 In article <21306@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes: .Not quite. The A3000 motherboard can be run at either 16MHz or 25MHz. Period. .Some come with a 16MHz 68030 and 68881, which wouldn't work at 25MHz. So the .motherboard gets a 16MHz clock, thus keeping the 68030/68881 happy. Just like .in the A2000, a coprocessor card can have any processor running at any speed .it likes. However, when that card talks to the A3000 motherboard, it must look .like a 16MHz 68030 if the A3000 is set for 16MHz, a 25MHz 68030 if the A3000 .is set for 25MHz. Since it was obvious early on that some coprocessor boards .might NEED, depending on design, to run synchronously to the A3000 motherboard, .and thus supply their own clock, we made it possible for a designer to let this .happen. So it's possible for a coprocessor board (68040, whatever) to run the .A3000 motherboard at 25MHz, even if it came stuffed for 16MHz operation. .However, in such a cranked up system, the original 16MHz 680x0 chips will have .to stay shut down. Dave, Is this a jumpered option or is it software selectable? I am guessing that this is going to be a jumper somewhere on the A3000 motherboard. What you are saying in effect is that the 16 mhz version of the A3000 will never run as a co- processor with the 60040 board, but will have to be replaced by the 68040 board, right? neil -- Only 3161 shopping days left till the next millenium! Neil F. Richmond INTERNET: celia!neil@usc.edu Rhythm & Hues Inc. UUCP: ...{ames,hplabs}!lll-tis!celia!neil)