ATmega128 CPU replacement - Better performance at same cost.

I moved this thread to a more appropriate location.

First, thank you for your involvement. I appreciate the interest about this project, but...

I have not intention of changing the architecture at this stage. There is no need for it anyways. This project has never been about making a powerful computer, it is about making a balanced one within a set of specific constraints.

Now about the AI junk part:

The ATMega128 is not an obsolete part, it is currently in production:

 

The so called 'drop-in' replacement only has 48 KiB of flash memory. How am I supposed to fit the OS that is currently 110 KiB in size? But yet again there is no point in replacing the CPU for a faster one, that would make the architecture unbalanced. There is more to the architecture than just the CPU.
Some members of the AVR DA family do have larger flash memories but 1. are not pin compatible, 2. they do not have external parallel buses for connecting to the rest of the system. Because the AI does not know about Micro-8 architecture, it makes false assumptions (read hallucinations).
The replacement FPGA for the YM2612 by Foenix has been discontinued for years as it made no business sense, I am very well aware of these, in fact I have had a couple units for test ages ago. Oh and btw Stefany sold her 8-bit business end of last year.
There is no AY in the Micro-8 architecture, and no need for it.

Now IF I ever run out of YM2612, I can easily integrate the Jotego core into the current system, I am very well aware of this and it does not require any architectural or PCB modification.
 

Bad location for thread because not full location options where possible at creation only a subset.

Ok for your ATmega128. A.I results says it is better for a simple 8-bits computer than a 100‑pin ATmega2560.

When ATmega2560 might be worth it :

• If you plan a large firmware (complex graphics, many protocols, or heavy libraries) where 256 KB flash and 8 KB RAM avoid tight optimization.
• If you want many UARTs/I²C/SPI and lots of GPIO for a very I/O‑rich system (multiple serial consoles, coprocessors, many peripherals on parallel buses)

Whereas the DA family : The pinout is different, code needs porting, great but....

AVR256DA64 Micro-8 project Impact

• Rewire everything: No drop-in replacement—your ATmega128 bus (Port A address/data, PG2 ALE) becomes flexible PORTC/D assignment on DA64.
• More flexible long-term: Route buses to convenient pins near RAM/video connectors; reassign peripherals without respinning PCB.
• Software change: Update DDRx, PORTx, PINx registers (PORTA→PORTH vs A-F); XMEM interface similar but different control bits.

Verdict: Great upgrade if starting fresh; 2-3 days porting for existing ATmega128 proto.

And yes i know S.Allaire history and Maximite too (STM32H7, they choose power).