(This is crossposted to comp.sys.sinclair and comp.os.cpm. Traffic is
pretty low so I didn't set a Followup-To.)
p3c80 is an output-only device driver for Locomotive's CP/M Plus for
the Sinclair Spectrum +3. It gives a true 85x24 terminal display (with
80-column and 64-column options also available) using an extremely
cramped font, just 3 pixels wide with no space between characters.
It's not ideal, but it's generally readable. More or less.
I realise that as the text can be hard to read, this isn't necessarily
something you'd want to use all the time - and you don't have to!
Using CP/M's "device" command, you can turn it on or off from the
command-line whenever you want.
The web page is here:
p3c80 itself is a FID file (a device driver loaded when booting), but
it comes with a simple TAP installer so it's not too hard to get it
working. You do obviously need a bootable +3 CP/M disk for the
installer to write the files to. As far as I know, this specific
version of CP/M unlike others is NOT freely downloadable anywhere,
though I noticed that someone possibly-legit does seem to be selling
disk images still.