Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga Subject: Re: Message-ID: <12716@cbmvax.commodore.com> Date: 14 Jun 90 16:54:53 GMT References: <1990Jun13.224910.10653@uokmax.uucp> Reply-To: daveh@cbmvax (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 40 In article <1990Jun13.224910.10653@uokmax.uucp> drtiller@uokmax.uucp (Donald Richard Tillery Jr) writes: >...question about whether it is possible to "hack" 2 Megs of Chip RAM out of >an Amiga 2000/500. Possible? Yes. Practical? Roughly as practical as "The Rejuvinator" or other add-ons. >Is the "Fatter Agnus" the same Agnus as the one in the 3000 that is capable >of addressing 2 Megs of chip RAM? I don't know fat from felgercarb. There are four basic Agnus revisions, one in the "thin" 48 pin package, three in the "fat" 84 pin package. The three 84 pin versions I call 512K, 1Meg, and 2Meg Agnus, respectively. Some Chip people probably call the latter two "Super" Agnus. In any case, 512K and 1Meg Fat Agnus are pin compatible. 2Meg Fat Agnus is the one used in the A3000, and it's not plug compatible with an A500 or A2000 Fat Agnus. >If I do a piggy-back on the motherboard, can I attach the select line to an >extra address line on it and have my desired double memory or am I >(proverbially) "spitting into the wind?" First of all, you can't piggyback anything on an A2000 or A500 that uses the 256K x 1 parts. Agnus couldn't drive 64 memory chips directly. As for the machines with 256k x 4 parts, a piggyback would at least have a chance of working. However, 2Meg Agnus drives things differently than 1Meg Agnus, so you're going to need some external logic. 2Meg Agnus is really only designed to directly drive 16 1Meg x 1 parts. The A3000 supports 256K x 4 parts, but via external logic. That's not a big deal on the 3000, since extra logic was necessary anyway to get the 16 bit Agnus to talk to the 3000's 32 bit Chip bus. So you're not going to get 2 Megs of Chip RAM on any 500 or 2000 without considerable hacking. Not that there's anything wrong with considerable hacking if you don't mind the risks involved. > Rick Tillery -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "I have been given the freedom to do as I see fit" -REM