While I was looking at retro computer implementations on the Blackice Mx, I thought I would port the Apple I implementation.
The leds could do with a bit of tweaking, such as reducing the number to two and inverting the signals. Or removing them completely as there are already leds that come on when the buttons are pressed.
Here is the code:
Note that of the retro computer implementations I have recently done posts for, only the NES one uses the SDRAM.
I am looking at the other @hoglet implementations such as the Beeb, Atom and Z80 CP/M, all of which would need the SDRAM. They need a bit more work, and would be easier to use with support in the firmware for writing ROMs to flash memory.