Damus
mos_8502 :verified: ๐Ÿ‡จ๐Ÿ‡ฆ · 4w
Let's start simple. A MVC-compliant prototype of an Ultimax mode banked mapper cartridge would have one banked region for the VIC-II, and one banked region for program code. It wouldn't provide extra...
mos_8502 :verified: ๐Ÿ‡จ๐Ÿ‡ฆ profile picture
So you get your ROM chips. One of them is for code, one is for data. Use the '040 512KB flash chips for shits and giggles.

We can start with the same basic design as Magic Desk: a latch to set the bank for program ROM, and then add another latch for video ROM. Those latches set the high bits of the ROM addresses, and get written to using I/O addresses.
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mos_8502 :verified: ๐Ÿ‡จ๐Ÿ‡ฆ · 4w
Your boot code is actually in the graphics ROM, in bank 0 offset 0xFFFE: the reset vector. That has to point to 0x8000, the bottom of ROML.