From: lex@cc.gatech.edu
Jonathan Griffitts writes:
> You ask "what field . . . where constraints are so tight?" I'd say that
> almost every project has many hard, fixed constraints.
The argument is getting more and more about terminology, but please
recall that someone said something like "you cannot just increase
power -- it's a spec". There's a difference between a hard spec, and
a design attribute which is more important than usual.
> - If you're designing a disk drive, the outside dimensions are
> standardized and fixed. You DON'T get any extra space or power. It
> won't be a viable product if it busts outside the "form factor".
I'll give you the space, but not the power. People routinely buy
larger power supplies in response to power-hungry components.
> - If you're designing anything portable and battery powered, the
> dimensions are almost always part of the basic product requirements. In
> this case you also won't get any extra space or power. Think about the
> constraints on a digital hearing-aid or pacemaker (I've worked on both
> of those!), or even a cell phone.
Ah, you have worked on medical devices. Yes, I could see the space
constraints here.
I don't think you can generalize so far, however. For a walkman or a
laptop, you really can tradeoff battery life versus cost of
manufacture, or battery life versus number of features, or battery
life versus speed.
> - If you're working on office equipment, there's always pressure to make
> things smaller. Ease of maintenance also puts constraints on size and
> shape of internal modules.
I don't see space here being constraining; most office equipment seems
to be mostly empty space inside. The usual size spec is that it is
the big enough, not that it is small enough.
> - If you're doing consumer products, cost of manufacturing probably
> dominates every design decision. Often size is squeezed, too.
Yes, but these are not hard specs. You can, for example, decide to
make it smaller while using more expensive components. You can
increase the battery size to get rid of another component entirely.
> - If you're designing flight electronics for aerospace, you're often
> required to fit into an odd shape and size (whatever room was left over
> after the aerodynamics, mission payload, propulsion, fuel, crew, etc.
> are accounted for). You can't get extra space for electronics if it
> would be at the expense of aerodynamic shape, etc. The thermal and
> power constraints will be defined by the rest of the system.
> Maintainability and access will be an issue, too.
I grant this one. This one is interesting, though: you are making a
small part of a bigger system. At some level, a level that is long
past by the time you come on the scene, there was a decision made
about what the appropriate spaces will be, and at that point the
decision could have been made differently.
If you are making NASA's next experiment, then of course they will do
it from scratch. :) This example is more like making a new gyro for
Hubble, than for making Hubble itself.
> Just like in space probes, if you ignore efficiency and use up extra
> space and power, something will have to trade off for it. It may not be
> possible to make that tradeoff and still have a viable product.
Right. I never said otherwise. The question is, what is a good
trade?
> The "bloatware" philosophy works for PC and workstation software because
> of the peculiar economics of this time. It's easy to cite cases where
> this is going overboard and resources are flagrantly wasted, because the
> designers are accustomed to think the CPU power and memory are free and
> nearly infinite. When the advance of CPU and storage technology starts
> to level out, this mindset will probably have to change.
Call it peculiar if you like, but CPU cycles and RAM really are cheap,
and not just for PC's. Designers should recognize this.
Lex Spoon
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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