1. Memory isn't just slow because they went for capacity not performance (except vacuously), it's slow because of the laws of physics. c.f. L3 memory is made of the same stuff as registers but takes about 30 times longer to access.
2. No, adding lots of dumb cores makes no sense.
3. GPUs are useful because many tasks are embarrassingly parallel. Many more are not.
4. 'If we wrote better software' adding many more cores increases the difficulty of reasoning about software hugely. Many tasks are not easily performed in parallel, or the speedup is not impressive enough. Most operating systems (my guess is that OS X is included) will choke if you give them too many threads - performance drops hugely, or many threads are left totally idle. This is due to lock contention etc.
5. Of course no-one 'needs' that Haswell logic - but it's sure nice having my computer do stuff quickly. My top-of-line phone struggles to play through its animations properly, and loading websites frequently takes a while. Good-enough is not really a good place to be. Furthermore, greater performance motivates more demanding applications.
6. We dedicate everything to offsetting slow memory because it's the only way to get good performance from the majority of tasks. Sure if your task can be handled by a GPU, by all means run it on a GPU. For those that cannot, we have a CPU.
There's a reason why the iPhone and iPad only have two cores - it's not worth their while adding more but does add lots of cost and complexity.
> Memory isn't just slow because they went for capacity
> not performance (except vacuously), it's slow because
> of the laws of physics.
Yes. The farther away RAM is from the CPU code, the more stuff needs to happen before it can get into those precious, precious registers. Even if data from main memory didn't have to travel over a bus/switch/etc between the DIMM and the CPU, it's not physically possible (in any practical sense) to have main memory running at anything close to the speed of the CPU once we're talking about multi-GHZ CPUs. DIMMs and the CPU are running on separate clocks, you have the sheer distance and the speed of electrons through the metal to consider, etc.
> There's a reason why the iPhone and iPad only have two
> cores - it's not worth their while adding more but does
> add lots of cost and complexity.
Yes! There's a reason why the A7 in my iPhone 5S blows away the quad-core ARM chip in my 2012 Nexus 7. That reason is because "adding more dumb cores" is not the answer to anything, aside from marketing goals.
