Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!uccba!uceng!dmocsny
From: dmocsny@uceng.UC.EDU (daniel mocsny)
Newsgroups: comp.arch
Subject: Re: Memory utilization & inter-process contention
Summary: Special purpose vs. general purpose; fragmentation
Message-ID: <2108@uceng.UC.EDU>
Date: 7 Sep 89 21:19:40 GMT
References: <1114@aber-cs.UUCP> <278@baird.cs.strath.ac.uk> <2089@uceng.UC.EDU> <45344@bbn.COM>
Organization: Univ. of Cincinnati, College of Engg.
Lines: 59

In article <45344@bbn.COM>, slackey@bbn.com (Stan Lackey) writes:
> [A] fundamental [law] ... is "special purpose
> is always cheaper than general purpose [to do the same specific job]".
> In other words, if you want the best paging performance on a VAX, you
> get VMS.  Because UNIX is a general purpose tool, ie it was made to
> run on anything, it can't be as good on a specific box as an OS that
> was written and tuned to run on that specific box and nowhere else.

Agreed. But why can't the hardware be tuned to run UNIX? Why build
interesting hardware first, and then almost as an afterthought put
an OS on it that is going to give users a porting nightmare?

Another question is this: is *every* difference between VMS and UNIX
essential to the superior paging performance of VMS on VAX? In other
words, *how much* UNIX do we have to give up to get that paging
performance, compared to how much we are giving up?

> Giving up something is required for generality; no general purpose
> machine is going to run FFT's as fast as an FFT box that costs the
> same.

Ah, but not all incompatibilities provide any clear-cut benefit.
Indeed, I think the opposite situation is more common. Consider the
proprietary minicomputer market. Can any truly disinterested observer
claim that all the fragmentation there leads to any significant
functional differences? I'm certain some exist, but in the real world
can they really justify the massive loss to users caused by reduced
software availability, porting problems, heterogeneous network
nightmares, and so on?

In another newsgroup, I proposed the notion of horizontal vs.
vertical fragmentation. Certainly as technology advances, we cannot
expect to indefinitely remain compatible with obsoleting hardware,
protocols, etc. The incompatibility resulting from advancing
technology I call vertical fragmentation. This is an essential
cost of progress, which the gains of progress offset.

On the other hand, when several vendors follow arbitrary and
incompatible paths to yield systems of roughly equivalent performance,
they have horizontally fragmented the market. One does not need great
imagination to list hundreds of examples of this. Just look around any
multi-vendor shop. Horizontal fragmentation yields possible
short-term competitive advantages to some vendors at the cost of
greatly increased artificial complexity to the user. This reduces the
amount of wealth the user can generate, ultimately reducing the size
of the overall market for all vendors.

Finally, computers are, after all, general-purpose devices. Unless you
are building embedded controllers or selling to users with high
technical sophistication and stable plans, you face another
fundamental law: Most people have no real idea of all the things a
computer can do for them until they actually try them. If a computer
doesn't act as a window into the wider work of the programming
community, the user will simply fail to learn about all the unforeseen
benefits available out there. Again, this translates into lost wealth
to the user, leading to a smaller market for the vendors.

Dan Mocsny
dmocsny@uceng.uc.edu