[Info-vax] Whither VMS?

[Bill Gunshannon]

In article <7iv384F31nq9iU23 at mid.individual.net>,
	Bob Eager <rde42 at spamcop.net> writes:
> On Mon, 05 Oct 2009 20:15:13 +0000, glen herrmannsfeldt wrote:
> 
>> Bob Eager <rde42 at spamcop.net> wrote:
>> < On Mon, 05 Oct 2009 15:00:20 -0400, Richard B. Gilbert wrote:
>>  
>> <> It's not SUPPOSED to happen but Murphy says if it can it will!
>> 
>> A good rule for computing hardware in general.
>>  
>> < Yes...in that case, the manufacturer insisted there was no fault. < So
>> I wrote a microprogram patch....!
>> 
>> Reminds me of the story of one IBM computer sometime before S/360.
>> 
>> For S/360, the EX (execute) instruction is not allowed to execute
>> another EX.  An earlier machine allowed it with a loop so tight that
>> power cycling the machine wouldn't get out of it. (Core memory including
>> the address of the next instruction.) The only way out involved magnets
>> and opening the memory box.
> 
> I heard that on the Honeywell 516, a very tight loop (single instruction) 
> would burn out core. Never tried it though!
>> 
>> I know the PDP-10 has XCT, and I thought VAX would have one, but I don't
>> see it in the book.
> 
> No, I don't see it, and I think I would have remembered it since I pretty 
> well immersed myself in the VAX instruction set when writing a compiler...
 
Sounds like the HCF instruction reported to exist in some (in particular
Motorolla) microprocessors in the dim dark past.

bill 
 
 

-- 
Bill Gunshannon          |  de-moc-ra-cy (di mok' ra see) n.  Three wolves
billg999 at cs.scranton.edu |  and a sheep voting on what's for dinner.
University of Scranton   |
Scranton, Pennsylvania   |         #include <std.disclaimer.h>