Agnus and Denise Rebuild

[Zac67]

In hardware, only Denise would have to be changed. In software all graphics related stuff would need to be rewritten (graphics.library, intuition.library?, application code banging the hardware). This is also necessary for RTG cards (most use chunky modes, too). The only way to go compatible is to add chunky modes and keep the planar ones. (IMHO missing this opportunity on the AGA chipset was a big mistake; software support could've been added later.)

OTOH, adding an RTG card takes care of the same problem, usually adds a lot of 'chip' RAM and allows for faster processing. So if you're not talking about recreating the Amiga and adding chunky modes en passant (e.g. Minimig), the RTG path would be the smarter one.

[Zac67]

Forget about upgrading the A500 chipset - it lacks bandwidth badly. Implementing an 8 bit planar and/or chunky mode would eat up ALL chipset bandwidth during scanline DMA. Plus, it would probably also need an Agnus rework to enable the bitplane DMA.

A reworked Paula could in theory support HD floppy disks (1.76 MB for Amiga format) - but you'd have to rework DMA scheduling in Agnus since the allocated DMA slots are not enough for HD bandwidth (would probably screw up Agnus timing completely, that's why C= went the 'half speed' way).

You're surely much better off with Natami since it improves the whole design, not just single aspects.

[Zac67]

Indeed. And Zorro III was way better than EISA in any respect - PCI didn't exist yet.