Very big XMas news for every fan of my LM80C Z80-based homebrew computer! After some months of development, today I finally released the firmware and schematics of a new version of my computer, the LM80C 64K Color Computer. As you can imagine, the main improvement is the RAM, grown from 32 to 64KB. After the BASIC has been loaded, about 43K are free for user programs. If you want to work with machine language, the whole amount of RAM is available to the user. Another improvement is the ability to switch between 2 VRAM banks, to keep at the same moment 2 complete video buffers ready to be used. 

Also, there are several improvements on the software side:

• improved mechanism to manage the serial buffer overrun, when the remote device sends data too quickly;
• new key auto-repeat to help typing;
• added support for INSERT key, to insert empty spaces into the text lines to add new chars w/o overwriting the rest;
• improved LIST command: now, if the user asks to list until a line that it's not present into memory, now the listing is halted at the line immediately before the missing one;
• added support to BASIC for serial channel B;
• code revision to comply with the Z8DK assembler;
• preliminary support for an external mass storage device (Compact Flash);
• mechanism to enable/disable the I/O buffer of the DOS, to recover 512 bytes.

Source code, precompiled firmware, and schematics are available at my Github repo.

[caption id="attachment_1903" align="aligncenter" width="300"] LM80C 64K Color Computer: prototype on breadboard[/caption]