And one more printer buffer based on the z80 that I found info on is PBUFF by Don McKenzie.

The code and schematics are no longer on the website at but can be found on wayback.

from a forum post:

I designed a Z80 product for operation with 4Meg of Dram which used only 
a 74LS00 and 74LS04 for interfacing to the Drams.

Without additional hardware support, it was possible to go to 64Meg, but 
I never tried it.

This was in a commercial product called PBUFF, which was a centronics 
port driven printer buffer.

The Z80 was getting a bit long in the tooth, and the need for large 
buffers, was overcome by manufacturers building more memory into their 
printers, so the product was dropped eventually.

Sold 1000's of units world wide, well before the internet days.
Also featured in Australian Electronics magazines, such as Silicon Chip. 
Around 1989 I think it was.

schematics and source code at:

Please don't contact me for additional support. I am somewhere between 
old age and death these days, so I have trouble remembering it all, but 
you are very welcome to make use of the information on the pages and 
files. :-)

Cheers Don...

Don McKenzie