🚀 go-pugleaf

Our news feed missed the beginning of this thread, so I never saw the original
posting.  But, I'll toss out some numbers to kick around.

Our current high-end machine is an 8-CPU shared memory symmetric
multiprocessor.  The FCS cycle time was 6.5ns, but I don't know what we are
currently shipping them at.  The CPU pipeline is capable of issuing an 
RX-format instruction every cycle, which is equivalent to a load immediately
followed by an ALU operation.  The machine holds 2GB of 25ns main storage, 
and 8GB of 80ns extended storage.  It supports 4 I/O processors, each of
which can handle up to 128 channels.  Both high-speed fiber-optic and older
parallel 370 channels are supported.

I won't argue a lot about CPU performance, because our metrics are different
from those used by the non-IBM compatible markets. 

As far as memory and I/O are concerned, PC's in general still can't support
more than 16MB of RAM.  A SCSI controller with DMA support provides about 
the same functionality as a mainframe I/O channel.  In theory, you can put
more than one in a PC, but the bus can't really support it at that point.

So, divide 10GB by 16MB and you get something in the range of 640 PC's to
match a mainframe on memory.  If you're concerned about I/O, it'll take 
about 512 PC's to match the mainframe.  I could also dig up the numbers on
weight and power consumption, but those are too scary to think about.

On a side note, someone mentioned interrupt handling capability.  The IBM
390 architecture has complex facilities for batching up multiple interrupt
events and distributing them across multiple CPUs.  This is a major win
when it comes to running thousands of I/O devices at the same time.

-- 
John Sullivan, Engineer/CPU Development  |  "Fools!  I'll destroy them all..."
Amdahl Corporation, Sunnyvale CA         |  jjs40@cd.amdahl.com, (408)746-4688