Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!uccba!ucqais!ggibeau From: ggibeau@ucqais.uc.edu (George Gibeau) Newsgroups: comp.sys.amiga Subject: OBESE AGNUS in a 1000 Keywords: fatter agnus, A1000, hardware hack Message-ID: <1749@ucqais.uc.edu> Date: 24 Jul 89 21:37:18 GMT Distribution: usa Organization: Univ of Cincinnati, College of Business Admin. Lines: 91 The following is an article published by Greg Tibbs (who as reported by Marco Pappa) is doing a hack to use the new OBESE Agnus (1 meg chip ram) on the 1000. Greg is president of a local computer club. He has a prototype running and will probably demo it at our next meeting (OVAUG). *************************************************************************** The Amiga 1000 Upgrade Project by Greg Tibbs Commodore has been working on what is called the enhanced chip set - an improved Agnus and Denise chip which adds several new capabilities to the Amiga. Unfortunately, the Agnus chip used in the A500 and A2000 is different from that in the A1000. Since the new Agnus allows the machine to have up to 1 megabyte of Chip (graphics) RAM, it effectively means the A1000 is obsolete. Well, I heard all the yelling of people at CBM and decided to try adapting the chip. I worked out a design and have a prototype PCB that works. The following is a description of the project called the Rejuvenator!: 1 I plan to create a daughterboard which replaces the A1000 WCS (Write Control Store). It will be larger as it will include standoffs for the Agnus, Denise, and Paula chips. Even so, the layout will be made to minimize conflict with existing internal expansions. 2) It will require 8 256Kx4 Dram chips to yield 1 Mbyte. The way !CAS is handled on the motherboard prevents it from being used with the new chip. However, by raising Denise and Paula, along with the new fatter Agnus, the old 512K chip Ram can be easily made into 512K of Fast Ram at C0000H (so it will Autoconfigure). For those of you with Spirit boards, provision will be made for addresses or to disable the old chip RAM completely to prevent conflicts. 3) Because the WCS will be removed, there will be a socket for the CBM A500/A2000 style ROM with extra addressing pin supported for the time that CBM goes to 512K byte ROMS. This might require a PAL change, but no rewiring. 4) Two jumpers determine the behavior of the board; One selects WCS/or ROM. If WCS is selected, the motherboard RAM becomes 256K fast RAM, addressed at 0F80000H, and 256K Kickstart RAM. If WCS is not selected then the 1.2 or 1.3 ROM will be activated. The remaining two jumpers will determine the address of the 512K RAM. For persons having performed the 1 meg motherboard RAM piggyback upgrade, two of the 4 addresses specifically address 1 Megabyte of fast RAM. 5) The OKI clock chip that CBM uses in the A500 and A2000 is supported. 6) If 1 through 4 are implemented, the A1000 will have 512K of Chip and 1 Meg of Fast, the 1.3 ROM, and the battery backed clock chip. Since all decode logic will be PAL-based the timings should be the same as on the old A1000. 7) This project will also have a minimal A2000-style video slot. It will be a subset of the A2000's due to lack of Audio and parallel port access. The Rejuvenator's video slot will run MicroWay's FlickerFixer with no modifications or additional wires from the motherboard. There are provisions for up to 11 jumper wires to the motherboard to supply signals for the video slot if they are needed. 8) Through careful and ingenious design, there are *NO* trace cuts on the motherboard. For basic operation, only two jumper wires are required to connect to the motherboard. These are the 28 MHz clock and a clock synchronization reset pulse. The OKI clock chip will require an additional jumper wire to obtain the necessary 12 volts. 9) A socketed PCB (no chips) and a separate chip kit will be made available to avoid FCC problems. 10) Hopefully, I'll have the prototype at the meeting to show it off. -Greg Tibbs ************************************************************************* I will post a message as to how it works if he demos it at our meeting this Tuesday (the 25th). He will probably be making this available as a LUCAS type project (shareware hardware). Greg is on BIX, not sure of address, but I can pass along any interest to him. He will also be at AmiExpo in Chicago and hopes to have a working model with him to show off. I will be there too, so look for a large group of loud folks from Ohio :-). George Gibeau -- Definition of HELL - A room full of MACS with all the right software ............on 5.25" disks ;-) UUCP: ucqais.uc.edu!ggibeau BBS: (513) 721-7977 GT NODE: 006/005 US Snail-Dept of Biology ML 06, University of Cincinnati, Ohio 45221