🚀 go-pugleaf

In article <32580026@hpcuhe.cup.hp.com>, edwardm@hpcuhe.cup.hp.com (Edward McClanahan) writes:
> peter da silva writes:
> 
> > The NeXT and the Amiga 3000UX have the same problem here: they're 68000
> > based, so you won't expect any outstanding improvements in the next few
> > years. Even if NeXT and Commodore make like Sun and switch to RISC processors
> > your existing machine is likely to be left behind. Though the asynchronous
> > bus on the Amiga means that a RISC coprocessor board would be quite a
> > workable compromise. The NeXT bus is much slower, more designed as a
> > peripheral bus instead of a general backplane like the Amiga's.
> 
> Is this true?  I understand that NeXT uses a 25MHz NuBus (2.5 times the NuBus
> used in the Mac II series).  Besides, a RISC coprocessor board would primarily
> access on(its)board memory and not be limited by bus speed.
> 

I have seen this statement over and over again "they're 68000 based, so you 
won't expect any outstanding improvements in the next few years"

This upsets me since the relative performance of the 68040 over the 68030
was over a 100% improvement in speed at the same CPU speed, according to
some of the journals I read about 1 year back. Motorola expects another
100% speed increase with the release of the next 68K CPU. This may be another
year away, but I think it is worth the wait.

A 25 MHz backplane is a quick backplane, definitely not slow! The analog bus,
while superior in many ways, doesn't mean that it is any slower. I syncronous
25 MHz bus and asyncronous 25 MHz bus should be about the same speed, but
the analog bus should be slightly slower due to the handshaking needed which
is not required for the syncronous bus. Am I off target here?

The main advantage of an analog bus is the ability of the other cards over
the bus to run at a slower speeds. All the cards on the bus who are using
the bus (master and slave card during the communication) operate as fast
as the slowest card can communicate. With a syncronous bus, all cards must
operate at the same clock rate, which means problems when you start 
increasing the clockrate of the CPU on the bus, in general. Thus, the
reason why most high performance systems out there are on VME bus for the
Motorola CPU. How accurate is this assessment?

							Dave Halko
-- 
   _________________________________________________________________________
  / "The use of COBOL cripples the mind; its teaching should, therefore, be \
 /  regarded as a criminal offence."           E.W.Dijkstra, 18th June 1975. \
+-----------------------------------------------------------------------------+
 \  "Have you purchased a multi-   halkoD@moravian.edu  Have you booted your /
  \ media machine from IMS yet?"   David J. Halko       OS-9 computer today?/
   \_______________________________________________________________________/