Came across these in a chess machine context, in a mostly German-language wiki

DC65 - 12.5MHz (or 10MHz?) 6502 emulator Apple ][ card from 1984, maybe DM3000 (follow link for advertisement text)

TK20 - 18MHz 6502 emulator (bitslice? 100 chips?) box from 1987, connected by umbilical to the cpu socket of a 6502-based chess machine, DM1600

Inventors were Heinz Schaetzle and Herbert Bsteh, said to be patented but I can't find the patent.

At least the TK20 would seem to be an in-circuit emulator which includes enough RAM to upload and emulate the whole system, which presumably stays off the bus while computing and slows down to perform I/O on the mother system.

Edit: Heinz, not Norbert.

As a side effect of our 65F02 accelerator project, it seems that my chess-computer-savvy friend Roland and I will get our hands on a Schaetzle & Bsteh TK20 for a while. (On loan, to have a loong, curious look and ideally help to make it operational again.)

I am really curious what technology is inside, and will report here! Conceptually, it is said to be quite close to the 65F02 -- fast RAM on board to upload the host computer's ROM upon each startup.

That's excellent - hope you get a chance to get some nice clear photos of the board(s)!

Will do!

To get an idea what to expect, I Googled for photos. Nothing to be found on the insides of the TK20, and while your link to the DC65 brings up a relevant discussion thread, that unfortunately has a broken link to the advert. But I found the advert and some photos of the DC65:

http://www.ralf-kiefer.de/A2/DC65/DC65_Inserat.png
http://www.ralf-kiefer.de/A2/DC65/DC65_Add_BS_sm.JPG
http://www.ralf-kiefer.de/A2/DC65/DC65_Base_BS_sm.JPG
http://www.ralf-kiefer.de/A2/DC65/6502- ... -oben.jpeg

Lots of 74Fxx TTL, fast PROMs, fast RAM, and plenty of PALs... Let's hope the PALs or PROMs are not what is acting up in the TK20; retrieving any lost program/configuration data would be a long shot. I'll bank on my "It's probably something mechanical" troubleshooting mantra...

You wouldn't have "binged" too much This board is mine, the web site too.

My question until now is if this is the last and only board?