4x3. Keyboard characters only (plus a very few extras). the @ symbol is a solid 4x3 block, which actually works fairly well. all lowercase letters, including p,g,q, (but not including the tall ones: t,i,d,f,h,j,k,l,b) are 3x3; and all are well-distinguished from upper-case. I don't think it's possible to make characters smaller than this... well, without limiting oneself to just uppercase or lowercase.
This is a cloneCapital letters here: https://fontstruct.com/fontstructions/show/1356385/fs-pixel-multilingual-1
See more:
http://velvetyne.fr/fonts/terminal-grotesque/
This is a clone of fs conscript_02I've been wanting to do this kind of font for ages, think of it as a soft square or a hard circle. Since it's been so long, I can't really remember the exact source of inspiration, but I do remember it had something to do with kix and his work.
The ability to kern now has obviously made the spacing better than it would have been otherwise. Thanks, Rob.