Metalguy66
New member
A while back, a guy named Wild Cobra on Amiga.org brought the following to my attention: As evidenced by the service manual schematics, with the right jumper settings, the rev 6a Amiga 500 is actually designed to accept an A3000 Agnus chip and a full 2 megs of ChipRAM on the motherboard!
This does require DRAM of a higher density (1meg x 4) than stock, but the additional address lines are already present on the motherboard both on the DRAM side as well as the CPU side of Agnus.
All that has to be done is to replace the Agnus chip with the A3000 part, remove the factory 256k x 4 DRAM chips, install four 1meg x 4 DRAM chips, and make the appropriate jumper changes to enable it.
Recently, I was able to verify that this does in fact work on real physical hardware in front of me. All of the "docs" I've seen on Aminet and elsewhere in the past have seemed to reflect that you need to build a quite involved hardware project in order to accomplish this. They are wrong.
So, for the benefit of all who may wish to have these instructions, please have a look at this:
note: Only an actual A3000 Agnus (one of the two part numbers listed in the diagram) will work. 2meg Agnus chips made for the A500+ or A600 will not work as they have a vastly different pin arrangement. I have done my absolute best to include all needed instructions/details in this single .jpg image. Enjoy.
This does require DRAM of a higher density (1meg x 4) than stock, but the additional address lines are already present on the motherboard both on the DRAM side as well as the CPU side of Agnus.
All that has to be done is to replace the Agnus chip with the A3000 part, remove the factory 256k x 4 DRAM chips, install four 1meg x 4 DRAM chips, and make the appropriate jumper changes to enable it.
Recently, I was able to verify that this does in fact work on real physical hardware in front of me. All of the "docs" I've seen on Aminet and elsewhere in the past have seemed to reflect that you need to build a quite involved hardware project in order to accomplish this. They are wrong.
So, for the benefit of all who may wish to have these instructions, please have a look at this:
note: Only an actual A3000 Agnus (one of the two part numbers listed in the diagram) will work. 2meg Agnus chips made for the A500+ or A600 will not work as they have a vastly different pin arrangement. I have done my absolute best to include all needed instructions/details in this single .jpg image. Enjoy.