[Simh] Problem with MT_ASTLVL on the VAX-11/780

[Paul Koning]

> On May 17, 2017, at 8:00 PM, Matt Burke <matt at 9track.net> wrote:
> 
> On 18/05/2017 00:18, Johnny Billquist wrote:
>> 
>> Hum. Do I remember wrong? I seem to remember that when you MOVB to a
>> register, the value should be sign extended. So not just the low byte
>> should have been modified.
>> 
>>    Johnny
>> 
> 
> I think you may be thinking of MOVZBL (and MOVZWL for words).

Or the PDP11, where indeed MOVB sign extends.

Is MT_ASTLVL defined as a register where only the low byte has meaning?  
	paul