Titokone is a simulator for the TTK-91 machine, developed at the University of Helsinki, Department of Computer Science as a part of a software development project course in 2004 by group Koski. The software has been published under the LGPL license, and you can get it at the "Computer Organization" course homepage.
Developers so far: Olli Alm, Seppo Hätönen, Sini Ruohomaa, Antti Takalahti, Sampo Yrjänäinen Arto Åkerlund, Tom Bertell, Johan Brunberg, Lauri Liuhto, Eeva Nevalainen, Harri Tuomikoski ja Jari Suominen.