[HECnet] TOPS20 on simh

Are there any HECnet'ers running TOPS20 on simh? Have you gotten the idle detection to work? I set up a TOPS20 system with simh (simh v3.8.1 on Ubuntu, TOPS20 v4.1 clean install). The installation went fine with no problems, but I cannot get the idle detection feature in simh to work. I say - pdp10 sim> att rp0 tops20-4.1.rp06 sim> set cpu tops20 sim> set cpu idle tops20 sim> show cpu CPU, idle enabled, stability wait = 20s, 1048KW, TOPS-20 sim> b rp .... Everything boots and runs fine, but simh uses about 98% of the host CPU and never goes down. In an hour of wall clock time the pdp10 process uses about 58+ minutes of CPU time. Clearly the idle detection isn't working for me. I did try posting this question on the simh list, but got no comments so I guess nobody there is using TOPS20. And yes, I could use KLH10, but AFAIK KLH10 has no idle detection feature at all. Thanks, Bob