Now I understand the graphics-ram - it starts at $0010.
Do you like my dino-head ? ;)
The board decodes the CS to the CRTC with a 74LS42:
- E880 and E881 enable the 6545 like in an ordinary 8032
- E882 writes the lo-byte of the graphics address
- E888 writes the hi-byte
- E88A writes 8 bits graphics the the RAM (screen-start at $0010).
The write to E88A is combined with R/W and with the 8MHz clock from QA of UD3.
The board plugs only in the 6545 socket and connect all pins except CS directly to the CRTC.
It adapts the charrom with all pins except CS.
There are two wires to BA1, BA3 to decode the graphics registers.
Also there are wires to UD3 QA (8MHz) and to RDY of the CPU.
16K SRAM board: