[Info-vax] Vaxes shutting off this week

[Stanley F. Quayle]

On 12 Mar 2009 at 15:14, Bill Gunshannon wrote:
> See my comments on the Strobedata Osprey.  The need for custom hardware
> was primarily because of the custom bus but that is reaally easy to get
> around.  Oh yeh, and for those not familiar with the Osprey, even though
> it is ISA or PCI it can access devices on UNIBUS or QBUS using an adapter
> that connects them to the PC.  

Hardware solutions can be required because they can replicate the exact timing of 
individual instructions.  This happens when code uses a delay loop instead of a timer.  
It can also happen with "magic" chunks of code that are sensitive to the CPU clock.  I 
know of one site where they use a variable-frequency clock to get the VAX to just the 
"right" speed.

Software solutions (like CHARON-VAX) attempt to run as fast as possible.  They can be 
slowed down, but don't have instruction-level granularity.

--Stan Quayle
Quayle Consulting Inc.

----------
Stanley F. Quayle, P.E. N8SQ  Toll free: 1-888-I-LUV-VAX
8572 North Spring Ct., Pickerington, OH  43147  USA
stan-at-stanq-dot-com   http://www.stanq.com/charon-vax.html
"OpenVMS, when downtime is not an option"