> Also notable: Original Playstation (AKA PS/1) compatibility was provided by simply putting a whole PS/1 on the board
The IO co-processor of the PS2 was built using the PS1's architecture so it could double as a PS1. Rather clever and efficient design, two generations of consoles in one, using the weaker previous generation console as a co-processor instead of a bolted on afterthought.
The Sega Mega Drive did something similar, normally the Z80 is just a support CPU used to run sound (although the 68000 could also talk to the sound chips, so some games run sound off the main CPU to varying degrees). But with the Master System converter, it's the main CPU for backwards compatibility. The converter itself is largely passive to adjust for the cartridge connection differences and adding the pause button, all the backwards compatibility is handled by the main system.
On the PS2 side, apparently later systems replace the original IO chip with a PowerPC based chip running a MIPS emulator, which is kinda wild in itself.
If the Power Base Converter is largely plastic why do they seem so expensive on the used market? I would imagine tons of clones would be available by now.
There seems to be one IC on the PCB in addition to the passives. Maybe this is some hard to clone chip?
They were never popular and sold poorly. Few people had a Master System, and even fewer wanted to play those games on a Genesis. Sega kept advertising it, as a statement more than anything. That explains how hard it is to find one.
I am not sure why that is the case. I used to have one that was a cheap small converter cartridge. To explore how it worked, I was amazed to see that there where no chips on the board but merely contacts and traces.
As another comment already states: for the most part, no.
However, the GBA CPU (an ARM7) in a DS is used as the IO-processor for DS games, while an ARM9 is the main chip. On the 3DS the ARM9 is the co-processor, while a new ARM11 is the main application processor. Since the 3DS can also run DS games it still has an ARM7 as well and can natively run GBA games, even if that functionality was barely used by Nintendo.
The problem with GBA functionality is you lost the ability to go back to the home menu; you had to force reset the console to exit. I think that’s why Nintendo only used the GBA mode under duress, and only once.
The IO co-processor of the PS2 was built using the PS1's architecture so it could double as a PS1. Rather clever and efficient design, two generations of consoles in one, using the weaker previous generation console as a co-processor instead of a bolted on afterthought.