Amiga 500 Rev. 5 1MB Chip Mod

[Sinphaltimus]

I know but to be honest, there really aren't many resources out there. So I thought I'd throw one here.

https://www.facebook.com/SExmortus/posts/10206970892982775

Amiga 500 Rev5 Mainboard, 1MB chip mod.

First I have to replace the old Fat Agnus chip (8370) with a newer Fatter Agnus (8372A).

Replacing the 8370.
(Video)
https://www.facebook.com/SExmortus/videos/10206970899342934/

Next I have to cut the JP2 trace between the middle and left (lower) pads next to the CPU and ROM chips. This trace tells Agnus to be ready for 512k (the way it is connected now) or 1MB chip (the way it will be after I connect the middle and right (upper) pads. If my male pin headers were here I would have just installed pins and a jumper.

To give you an idea of the scale we are dealing with here. That's the tip of a razor sharp Xacto knife blade I'm using to cut that trace. I can no longer see well enough to do these things without the macro zoom video and light of my Galaxy Note 2. Sorry video is upside down.

Video:
https://www.facebook.com/SExmortus/videos/10206971136908873/

And I'll skip over a few things. First, I tried using the "Conductive Ink" trick but that didn't pass continuity like it should have. The ink pen was at least 8 years old and I really had to abuse it to get some ink out so there's that. Anyway, I'm just cleaning it up now getting ready to spot solder the pads.


https://www.facebook.com/SExmortus/videos/10206973206760618/

And of course I do something I do not like..

https://www.facebook.com/SExmortus/videos/10206973265002074/

Cleaning up my mess.

https://www.facebook.com/SExmortus/videos/10206973407605639/

Now it's time to cut another trace..

https://www.facebook.com/SExmortus/videos/10206976442641513/

Done and clean... Time to check my work...

And done.

[towmater]

When one replaces a Fat Agnus with a newer version, do any of the other custom chips need updating? Or would there be any benefit to adding a newer Denise for example, even if it is not required?

[Sinphaltimus]

When one replaces a Fat Agnus with a newer version, do any of the other custom chips need updating? Or would there be any benefit to adding a newer Denise for example, even if it is not required?

I don't know. I haven't looked in to that yet. I think you can go from ocs to ecs but that will take dine digging to verify.

 

I haven't done this in a very long time.

Edited September 17, 2016 by Sinphaltimus

[+OLD CS1]

@towmater @Sinphaltimus Resurrecting this, no, you do not have to upgrade any other custom chips.  However, if you have a "Fatter" Agnus you should upgrade to the Super Denise 8373, as well.  It provides a new color mode "extra half-bright," or EHB^*, as well as additional screen modes utilizing higher bandwidth.  I purchased a Super Denise back in '96 or so to play Death Mask and try out Productivity Mode.

 

"Fatter" (1MB,) "Obese" (2MB) Agnus and Super Denise comprise the ECS, enhanced chip set.

 

* I have read that a later revision of Denise 8362 supports EHB.  It is possible this revision over-lapped with the production of Super Denise.

Edited October 26, 2021 by OLD CS1
@'ing people for attention.