🚀 go-pugleaf

>From article <33B8C6...@pce.net>, by Micheal Peters <mich...@pce.net>:
> Rashid J Al-Ali wrote:
>> 
>> I am wondering, why people would use Mainframe computers.?
>> What are the major reasons for using mainframes.?
>> And what are the type of applications that mainframe would be used for?
> 
> Well up untill recently Mainframes could crunch large formuls and
> numbers faster and more percice (gerr.. Missing my spell checker). 

Nah.  A DEC Alpha is still the fastest single CPU on the market, and
mainframe CPU speed hasn't had much of an edge on microprocessor CPU
speed since the mid 1980's.

Where mainframes really win is in massive I/O bandwidth.  If you want
multimedia servers, with huge disk farms and massive network bandwidth,
a mainframe may serve you better than the competition.  Even here,
though the super-micros built by folks like SGI and HP are chewing
away at the edge once held by mainframes.

If you're stuck cramming your I/O through a SCSI bus, you'll never match
the performance of a system with multiple independent main memory busses
and multiple DMA channels that can move data at memory speed without
noticably slowing down the CPU.  Of course, even in this arena,
minicomputers of the 1970's began to nibble at the mainframe market
(the Modcomp IV computer, a 32-bit mini delivered in 1974, had 4 memory
busses, 2 for I/O and 2 used by the CPU, one for instruction fetch and
one for operands).

If you've got a legacy of ancient COBOL code, some of which was last
compiled 30 years ago and the source code itself is lost, you're likely
to want a mainframe!  IBM and UNISYS still make good money selling
mainframes to folks in that bind, where performance isn't the issue
but compatability is everything.

					Doug Jones
					jo...@cs.uiowa.edu