colas@lemur.inria.fr (Colas Nahaboo) (03/06/91)
After querying the net, I finally got the info I wanted from Darrell Grainger! Here it is: WARNING: this WILL void your warranty, and you could seriously damage your amiga if you don't know what you are doing. Do this at your own risks! Look at the schematics at the end of your A500 user manual, you will clearly see of what lines Darrell speaks. ------- Forwarded Message From: darrell@comcorp.uucp Subject: Re: Updating the A2000 Date: Fri, 1 Mar 1991 11:09:12 -0500 To get the Amiga 500 to recognise the A501 (or equivalent) memory as CHIP memory, you need the 8372A Agnus chip. The 8370 Agnus is NTSC and only addresses 512K of memory (the 512K on the motherboard). The 8371 Agnus is PAL and only addresses 512K of memory. The 88372A can switch between NTSC and PAL and addresses 1M of memory (the 512K on the motherboard and the 512K in the trapdoor). The 8370/8371 Agnus does not have enough address lines to physically address 1M of memory. The 8372A has enough address lines to handle 1M of memory by the A501 memory must be reconfigured. This is done by changing some address lines between the Agnus, 68000 and Gary chips. You need to change two things. First, pin 32 of the Gary is connected to ground. This connection must be cut. Looking at the motherboard, right near the A501 connector (CNX) you will see a trace from front to back of the machine and ends near the CNX (actually it goes through a hole on the motherboard to the underside of the board). the trace is about 3 cm long. Cut this trace with a knife (don't cut too deep, just enough to break the trace). To confirm you have the right trace try testing the resistance between the end of the trace and pin 32 of the Gary chip. There should be little or no resistance. Also, once you cut the trace you can test the resistance to see if it was a good cut. The resistance should be 100%. Second, pin 59 of the Agnus must be changed. Right now this pin is connected to pin 39 on the Gary and pin 52 on the 68000. On your revision motherboard there should be a jumper between the Kickstart chip and the 68000 (kickstart is part number 315093-01 or 315093-02). This jumper is a trace in three parts (three little squares). The first and second square are connected and the third square is off by itself. What you need todo is cut the trace between square one and two then solder together square two and three. What follows is a basis diagram of what I just described. Argh... forget the diagram... you should be able to figure it out from the description. If you cannot find the traces I am talking about then here is how you do it on boards that do not have the jumper between Kickstart and 68000. Cut the trace going from pin 59 on the Agnus to pin 52 on the 68000 as close to the Agnus as possible. Use an ohm meter to find the trace that connects these two pins together. On the bottom of the motherboard find pin 59 of the Agnus (this is the easiest place the find the pin and best place to put a jumper wire). From the pin 59 of the Agnus socket jumper over to pin 47 of the 68000. Your done. Please be careful and remember that this voids warrantee. If you don't know how is solder you can do some major damage and I will not be held responsible. The Amiga 500 is a multilayer board so don't use a soldering gun; use a proper electronic soldering iron. Be careful of static electricity too. Darrell Grainger ------- End of Forwarded Message -- Colas Nahaboo, colas@sa.inria.fr, Bull Research, Koala Project, GWM X11 WM Phone:(33) 93.65.77.70(.66 Fax), INRIA, B.P.109 - 06561 Valbonne Cedex, FRANCE.
raible@cbmvax.commodore.com (Bob Raible - LSI Design) (03/07/91)
In article <10380@mirsa.inria.fr> colas@lemur.inria.fr (Colas Nahaboo) writes: >After querying the net, I finally got the info I wanted from Darrell Grainger! >Here it is: > >WARNING: this WILL void your warranty, and you could seriously damage your amiga >if you don't know what you are doing. Do this at your own risks! >Look at the schematics at the end of your A500 user manual, you will clearly see >of what lines Darrell speaks. > >------- Forwarded Message > >From: darrell@comcorp.uucp >Subject: Re: Updating the A2000 >Date: Fri, 1 Mar 1991 11:09:12 -0500 > > To get the Amiga 500 to recognise the A501 (or equivalent) memory as CHIP >memory, you need the 8372A Agnus chip. The 8370 Agnus is NTSC and only >addresses 512K of memory (the 512K on the motherboard). The 8371 Agnus is >PAL and only addresses 512K of memory. The 88372A can switch between NTSC >and PAL and addresses 1M of memory (the 512K on the motherboard and the >512K in the trapdoor). The 8370/8371 Agnus does not have enough address lines >to physically address 1M of memory. The 8372A has enough address lines to >handle 1M of memory by the A501 memory must be reconfigured. This is done by >changing some address lines between the Agnus, 68000 and Gary chips. > > You need to change two things. First, pin 32 of the Gary is connected to >ground. This connection must be cut. Looking at the motherboard, right near >the A501 connector (CNX) you will see a trace from front to back of the machine >and ends near the CNX (actually it goes through a hole on the motherboard to >the underside of the board). the trace is about 3 cm long. Cut this trace >with a knife (don't cut too deep, just enough to break the trace). To confirm >you have the right trace try testing the resistance between the end of the >trace and pin 32 of the Gary chip. There should be little or no resistance. >Also, once you cut the trace you can test the resistance to see if it was a >good cut. The resistance should be 100%. > > Second, pin 59 of the Agnus must be changed. Right now this pin is connected >to pin 39 on the Gary and pin 52 on the 68000. On your revision motherboard >there should be a jumper between the Kickstart chip and the 68000 (kickstart >is part number 315093-01 or 315093-02). This jumper is a trace in three parts >(three little squares). The first and second square are connected and the third >square is off by itself. What you need todo is cut the trace between square >one and two then solder together square two and three. What follows is a >basis diagram of what I just described. > > Argh... forget the diagram... you should be able to figure it out from the >description. > > If you cannot find the traces I am talking about then here is how you do it >on boards that do not have the jumper between Kickstart and 68000. > > Cut the trace going from pin 59 on the Agnus to pin 52 on the 68000 as close >to the Agnus as possible. Use an ohm meter to find the trace that connects >these two pins together. On the bottom of the motherboard find pin 59 of the >Agnus (this is the easiest place the find the pin and best place to put a >jumper wire). From the pin 59 of the Agnus socket jumper over to pin 47 of >the 68000. Your done. > > Please be careful and remember that this voids warrantee. If you don't know >how is solder you can do some major damage and I will not be held responsible. >The Amiga 500 is a multilayer board so don't use a soldering gun; use a proper >electronic soldering iron. > > Be careful of static electricity too. > >Darrell Grainger > > >------- End of Forwarded Message > > >-- >Colas Nahaboo, colas@sa.inria.fr, Bull Research, Koala Project, GWM X11 WM >Phone:(33) 93.65.77.70(.66 Fax), INRIA, B.P.109 - 06561 Valbonne Cedex, FRANCE. Correction: the part you require is the vanilla 8372. The 8372A is the A3000 version with a different bondout. I believe that some A500 already have this chip on the later revs of the mother board. Those users do not need to obtain a new AGNUS(happy birthday :3) ). The 8372 is bonded out for the 1MEG chip RAM you seek. As for the rest of your posting your on your own, but I didn't see any other errors. I am not in a position to endorse the above course of action, but I did wish to correct an obvious error. To all you hackers out there GOOD LUCK!