[rescue] Slightly OT: Problems with simh and macbook

John Francini francini at mac.com
Mon Nov 13 11:21:07 CST 2006

The real problem is that most of the emulated OSes don't know that  
they're not running on the real hardware, so they are always doing  
something, even if it's the "null process" or "null job".

I have the same problem with KLH10, a DEC KL-10 emulator that allows  
me to run either TOPS-10 or TOPS-20.  That emulator adds a special  
'hardware' data movement instruction that, when called, simply puts  
the emulated CPU into suspension until a simulated hardware interrupt  
occurs (such as I/O completion or a clock interrupt). When that  
happens, the emulated CPU is continued.

By poking a call to this instruction into the TOPS-10 or TOPS-20 null  
job loop, the emulator's CPU usage drops from 100% of my Mac to less  
than 6% if the emulated system is idle.

I haven't played very much with SIMH, so I don't know if it supports  
that feature or one like it.


On 13 Nov 2006, at 9:53, Dan Williams wrote:

> I have been runing simh on a Macbook. I am having problems with the
> amount of processor time it takes up.  Anyone know of any Unix utils
> that can limit a program l ike this (I tried nice).
> I also remember reading a thread here about usb serial adaptors anyone
> have any recommendations for connecting to Sun/Vaxen machines. I am
> not that familiar with Macs.
> Thanks
> Dan
> _______________________________________________
> rescue list - http://www.sunhelp.org/mailman/listinfo/rescue

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