🚀 go-pugleaf

In article <128R02pn34lx01@JUTS.ccc.amdahl.com> jjs40@cd.amdahl.com (John Sullivan) writes:
> 
> 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.

Hmmm...  We regularly sell pc's with 32MB of memory, and an EISA bus
can certainly handle a couple of 32bit SCSI cards.  Many motherboards
now a days support 64MB of memory, and local bus SCSI boards are going
to up the performance a lot.  FDDI and such are making connecting
hundreds of pc's together more practical.  I would say that your
numbers are already off by a factor of 2-4 and they number of PC's
needed to "match" a mainframe is closing by a factor of 1.5 per year.


This is really a battle of "economy of scale" vs "economy of
locality".  It used to be much cheaper to by one 400MB disk than ten
40MB disks, but now with disk sizes exceeding 2GB and with the
incredible volume of PC's the cheapest way to by a 40GB disk is to buy
20 2GB disks and put them in a RAID.  Likewise with CPUs.  The IBM
370/158's were around 200 times faster than an apple II, but now the
fastest mainframe cpu is barely a factor of 2 or 3 faster than the
high end RISC chips and _much_ more expensive.  (CPU power as
measured by integer or floating point code, not memory bandwidth,
multiprocessing/interrupt stuff, etc.)  The easiest way to get lots of
MIPS nowadays its to use multiple CPUs, and many of the fastest
computers are going toward using pretty much standard PC CPUs.


By the year 2000, what people call a "mainframe" and the things they
will do with a "mainframe" won't look very much like what a
"mainframe" was when the term was coined.  Mainframes aren't dead, but
they are having to fight really hard to just to stay sort of alive.



-wayne