Hypervisor dreams - or what you can do with 64 bits

Long ago, in a processor far away, there were two parallel sets of registers.  By the magic of EXX, you could hide the current register set in a safe place, and work using another set.
I haven't looked at an ARM instruction set recently, but I expect there's something similar.  Probably working by switching the high and low 32 bits of a register around.  So each 64 bit register becomes a set of two, 32-bit registers.
So what could be achieved by doing this?
In the old days you could do interrupt processing.  When an interrupt happens, the current working registers are switched out, the interrupt is processed, and the registers switched back.
Or you could run two 32-bit apps at once by switching between 32-bit register "sets".
Or the OS could use one register set, and the app another.  Now that would be useful.  Is this what Apple are doing in iOS7?
These are variations on a hypervisor theme.
They are deep mysteries, the answers to which even iOS developers are not privy.

Why the Commodore 64 was 64

Many years ago, I used to program 8-bit computers.  The first thing to know about them is that they were 16-bit computers.  Sort of.  The Z80 inside the ZX Spectrum had 16-bit registers (the things that actually do the work inside the processor), and a 16-bit address bus.  A 16-bit address bus means you can specify any one of  65536 RAM (memory) locations to store or retrieve a number.  65536 is commonly approximated and abbreviated to 64K.  Hence the name of the Commodore 64.
Similarly, 16 bit registers mean you can work with numbers (integers) in the range 0-65535.  This is a very useful range of numbers for most things you'd want to count.
But then along came 32-bit processors, allowing a number range of up to 4 billion.  Not many calculations need to use numbers that big.  (And anyway, FPUs came in about the same time allowing you to do calculations with non-integers for things like calculating the national debt down to the last penny.) 32 bit processors can access 4 billion memory locations, today known as 4 Gigabytes. Smartphones like the iPhone5S currently have less than 4GBytes of RAM anyway, so 64-bit addressing is irrelevant.
But people have more memory than that in desktop computers, so the next step up was to go with 64 bits. Which is really overkill for almost everything.  (48 bits would have done the trick for real-world amounts of RAM.)
As far as the registers in the processor go, there's not a lot you can do with 64 bits that you couldn't do with 32.  Unless you can swap the high and low ends around.  Which effectively gives you more registers. This is a good thing because the more registers in the CPU, the less you have to access memory.  Memory access is slow, which is bad.
So Apples's new A7 processor basically has twice the CPU internal memory of the A6.  Which makes it faster.  If it's used.  Which it probably won't be.  Unless...

Must stop thinking about Apples

Can't help thinking that Apple have really messed up with the iPhone 5C. It would have made sense had it been about $100 cheaper than it is. But pricing it only about two monthly payments short of the S is just dumb. Wall Street seems to think so too. I really hope it's not just plain greed.

And what are those 'croc' cases? Jony spends a whole video explaining how nice the plastic is. Then they decide to cover it up? And the holes aren't even in the right places! Apples logo hole? iPhone wording hole? No.

It all smacks of "committee" to me.

I hope the 6 will come in bright plastic colours, with the fingerprint sensor too. And NFC. And a bigger screen.
Sad to think Apple may have totally lost it by this time next year. They really need some innovation this October.

Après apple September 10

Hmmm. Pleasantly unsurprised at the new fingerprint scanner. But that's all they had to show. Doesn't really add up to a years's worth of innovation. More bits in the processor is nice but who will notice a difference on a screen that small?
I'll just have to hope the motion processor has something to do with a forthcoming iwatch.
Somehow I don't think I'll be paying the £250 fee (to upgrade my iPhone5 a year early) just for that fingerprint sensor.

2013 September 10 apple event

It's three days before Apple hold an event to announce what they've been up to. Innovating, hopefully. But the signs aren't good. Despite Samsung and others releasing smartwatches, they probably haven't got round to that yet. So what will they announce?
A couple of new "colours" for iPhone 5s. Boring.
Fingerprint scanner? I'd be pleasantly surprised. iPhone 4S introduced Siri so they'll have to do something like this. Obviously, some spec numbers will also increase but no one really cares.
iPhone C model - C for colour/China/Cheaper. A plastic back in actual colours sounds good to me. I had much better signal from my 3 with a plastic back than either my 4 or 5 with all the metal. But no one is talking about what other differences there'd be in a cheaper iPhone. Internally it's likely to follow the iPad2 precedent and be an iPhone4. But no one wants that teeny little 3.5" screen.

And one more thing.

Would be nice. But I can't see what. Upgraded Apple TV etc. And iOS 7 date. About time. Yawn. Sad thing is, that's actually what I'm most looking forward to.