gauging interest in VAX 6000-530

From: Carlos Murillo <cem14_at_cornell.edu>
Date: Mon Oct 25 01:25:18 1999

At 07:56 PM 10/24/99 -0700, you wrote:
>Excuse me? Could you please back up this assertion with data? After all,
>at -some- point, all these busses have to get their data into/out of the CPU,
>right? And -that- is a "bottleneck" for sure... (Sure, you can have
>channel-to-channel I/O, but most aps are not just shuffling bits.)

Well ... I have some experience with high-speed switches and crossbars
in parallel supercomputers (as a user). The fallacy in your thinking is
that you believe that moving data around is not "processing". You still
think that the real processing takes place only at the cpu. Matter of fact
is that, in the real world, as data goes through each driver/buffer and
process in the OS on its way to the process that will actually do something
with it (i.e., actual "integer-op-related" cpu time) there are usually several
large block transfers. If all of this can happen without hogging the cpu
(and you need hardware to do it) you can bet that the corresponding machine
will be many times faster than a machine with a PCI bus.

I once read that the average number of moves for net data (after it is in
 memory) for data from input through tcp/ip stack through OS through
application is on the order of 4.x ... I think in some Sun literature...
Received on Mon Oct 25 1999 - 01:25:18 BST