CUBE		Control Universal took over Acorn's rackmount/Euroboard systems in about 1982. They produced a 6809 CPU card for their CUBE system and the BeebFlex system allowed them to be used as 6809 second processors. The BeebFlex is reviewed in Acorn User Issue 32 (March 1985). The ROM code shows that it does not use a Tube ULA or implement the Tube API.
Toal		Graham Toal's 6809 prototype second processor. Graham briefly described this on usenet and refered to Brian Jones making a breadbarded 6809 copro. The hardware uses the Tube ULA and the client code implements the full Tube API.
Client.src	26K	Have been inspired to finish the 6809 Tube client code I started writing in 1989. All main code written. Implements the full Tube API and communicates via a Tube ULA (or hardware that looks like a Tube ULA).
Dragon.doc  Dragon.txt	(MSWord) 650K (Text) 26K	"A Dragon In The Tube" An article by Huw Jones in Electronics and Computing Monthly, August and September 1985 describing an interface to use a Dragon 64 (or Dragon 32 with 64K memory) as a 6809 copro. This uses a single 8255 PIA as a single communication path instead of the Tube ULA. It does not implement the Tube API and uses the same interface API as Microsystems coprocessor.
msys13-6.doc msys13-6.txt	(MSWord) 1.6M (Text) 25K	"Designing a 6809 coprocessor for the BBC microcomputer". An article by Huw Jones in Microprocessors and Microsystems, Vol 13 No 6 July/August 1989 describing a 6809 copro. This uses two back-to-back 6821 PIAs as a single communication path instead of the Tube ULA and does not implement the Tube API.
Dis68 Mon68 MkSrc68	4K 11K 7K	BBC BASIC 6809 disassembler module, disassembler and source generator.