🚀 go-pugleaf

In article <347B0F29.2A8803D6@bigfoot.com>,
Lawrence <flowerpots@bigfoot.com> wrote:

> Tom Berriman wrote:
> > 
> > Rumour has it that a 9600/350 with RealPC runs at the same speed as a
> > Pentium <<One>> with MMX.
> 
> I'm glad this hasn't died!   All the
> reviews I read about VPC and the like
> suggest that on most applications,
> there is little noticeable speed difference
> between Mac/VPC and Pentium, and if
> any it's about 10-20pc slower!
> 
> Therefore 9600/350MHz being about 30pc
> faster than 266MHz should be faster.

I'm currently testing out VPC on a PB1400/166.  It runs at the speed
of a slow-ish Pentium.  Not fast enough to enjoy multimedia or to
seriously use any of Microsoft Office, but good enough for compatibility
testing and running the odd program that has no Macintosh version.  If
it runs that fast on a 166MHz processor in a PowerBook, it should be
pretty good on a 266MHz processor with a decent bus speed.

> I know the processors work in different ways and certain calculations are
> processed at different speeds etc... but it can't be as far off as some have
> suggested??
> 
> Can anyone tell me what RISC and CISC stands for.

Don't forget ... your Mac isn't emulating a Pentium ... it's running
one program that /simulates/ a Pentium and the rest of a PC motherboard.
There are a large number of differences between the processors, and the
details of how your Mac's processor emulates the Pentium and the rest of
the PC motherboard have complexity far beyond the range I can usefully
describe in this group.

CISC == Complex Instruction Set Computer
RISC == Reduced Instruction Set Computer

Processors (68000, 80486, Pentium, P603a, whatever) understand different
sets of instructions.  The really early processors (Z80, 6502) had a
small and simple set of instructions which were quite easy to decode and
interpret.  You could do very few complex things like looping and
array-indexing inside any one instruction.

As the chip-makers competed against one-another, the Z80 developed into
the 80486 and the 6502 developed into the 68030.  Both the latter chips
can do hideously complicated things in one instruction: what would have
taken ten or twenty instructions in the original processors can be done
in two or three instructions in the new ones.  Unfortunately, in order
to provide instructions that can do all these things, the chips have to
be CISC-based: cope with a lot of different instructions, each of which
can cause the chip to do many complex things.  This tends to make the
chip very large and complicated, and to increase the amount of time it
takes to figure-out exactly what the chip should do at any time.

Eventually, it becomes simpler to slim the processor back down, give it
a reduced (smaller) instruction set of very simple instructions, but
make the thing run like greased-lightning.  This RISC-based processor
can't do very much in any one instruction, but it can run a series of
ten instructions in the time that a CISC processor can run two.  Since
there are fewer instructions, the processor wastes less time trying to
figure-out exactly what it should be doing.  Since it doesn't have to
be as complicated, it can be smaller, use less power, etc..

Simon.
-- 
Simon Slavin -- Computer Contractor. | Excessive quoting from Shakespeare:
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