CPU/SoC considerations


ccssnet

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this is my first forum post. i was looking at the ziilabs.com cpu named zms-40 looks quite powerfull, i didnt dig into all aspects of analysis such as how its licensed but it sure looks powerfull.


please use this thread to collect other canidates and we can compare them.
 
Welcome to Pandoria!


Given that the will be no P2 for a couple of years yet, won't anything we find now be superseded by the time parts are being chosen for real?
 
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Power pc is as inefficient as x86. Arm ftw.
OK...1) Inefficient? I think that game system designers have a reason to always go with PowerPC in home consoles, and ARM in the handhelds. Why not try packing some power into a handheld? 2) What does ftw stand for? I checked Wikipedia and the only plausible association was "F**k the World."
 
For The Win ^^.


The Cell is great, but it seems it requires a lot of programming effort to get a really optimized code.


As an assembly fan, i'm fine with it, but it's probably a pain for coders.


Time is money.
 
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Power pc is as inefficient as x86. Arm ftw.
OK...1) Inefficient? I think that game system designers have a reason to always go with PowerPC in home consoles, and ARM in the handhelds. Why not try packing some power into a handheld?
The reason is that PowerPC is ineffecient and will therefore run hot and require a fan (ARM devices do not even need fans and most often don't need dedicated heatsinks, either) and will get you much less battery-life as a result of its power-wastage and requirement for active cooling, and that ARM is plenty powerful for what's required in a portable device. More importantly, ARM SoCs ("System-on-a-Chip", of which there are many - these are the basis of many, many portable devices, and also some computers too) usually have very good GPUs - my understanding is that there are fewer PPC SoCs, and that they don't have GPUs that are as good. For example,

https://www.youtube.com/embed/te8jt-jUkm8?feature=oembed&start=117 - the machine has a somewhat old ARM11 (ARMv6) CPU, but it's coupled with a GPU that allows for a lot.

The other point is that in a home-console, there's room to put the CPU and other components to handle other things, and there isn't a requirement not to drain a battery. There isn't room for this on a portable device, which is why SoCs are used in the first place. Since this is the only way to do things, why would you choose a less-powerful, less-flexible PPC SoC, when you could use an ARM one?
 
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OK, well thanks for the pointers. Makes much more sense now! :) Hmmm. How'bout AMD! Don't they make SoCs?
 
X86 will never be as powerefficient as arm. Put an amd or intel soc into a pandora and you will get a much worse batterylife, maybe not even 1/4 of what it has now. Intel and amd are using cpus like the atom for low power devices, but they are years behind arm.
 
OK, well thanks for the pointers. Makes much more sense now! :) Hmmm. How'bout AMD! Don't they make SoCs?
Brazos has around a 9 Watt TDP which is supposed to be brought down to around 5 Watt in more integrated solutions ala Z-series APUs. This is too much heat to be reasonably handled within the Pandora's form factor. You'd need to increase the size to where it wouldn't really be pocketable in the normal sense of the word as a result.

ARM SoCs are designed in order to fit within an appropriate thermal envelope, and tend to consume less then 2 Watts. If I'm not misremembering things the current Pandora SoC is rated at around 0.1 Watts. They benefit from considerable engineering effort dedicated specifically to squeezing the most performance out of a small thermal envelope which makes them particularly appropriate to handheld devices. This doesn't mean they have raw power comparable to CPUs that consume more power, but they do give a good accounting of themselves relative to power used.


The real issue though is you want reasonable thermals particularly with a large piece of polymer impregnated battery sitting in your hands that can do very bad things if it gets too hot.
 
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OK. ARM just isn't really compatible with the OSes I like, but I can make do.
 
Perhaps sometime in the future... (far far future?)


But for now, the OSes you like are simply not an option in the Pandora form factor (or anything on this scale).


I wouldn't hold your breath waiting for it to happen either. Besides, with factoring in exponential growth, the trend towards miniturization, portability and power efficiency... my money's on ARM all the way.
 
If I'm not misremembering things the current Pandora SoC is rated at around 0.1 Watts.

That'd be pretty nice wouldn't it ;p You can see the maximum power consumption in the datasheet (p122) and the big two power domains are 994mA and 439mA respectively w/Smart Reflex on. Smart Reflex dynamically adjusts the voltage so it's difficult to say what wattage that corresponds to, but it's probably well over 1V typically given the nominal values w/Smart Reflex off. There's also another few hundred mA for the other domains which are going to be around 1.8V or 3V - a lot of these are I/Os and many of them will usually not be active, but if you have something like TV out going you could be running the video DACs constantly, for instance.


This is worst case for temperature (90C) and everything firing. In practice it'll be a lot lower, especially since the DSP and SGX are usually doing nothing or close to nothing in Pandora. To get 10 hours battery life it won't be drawing more than about 1.5W, and the LCD only uses a few hundred of those, so I expect the SoC + RAM probably use around 0.5 to 1W while under a decent active load.
 
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OMAP5 looks like the obvious choice. But a SoC with more powerful GPU like the 'Rogue' series would be very nice, like ST-Ericsson's A9600. I'm guessing it could handle PCSX2 if it gets ported ARM architecture.
 
I think the next omap after omap5 will be the soc of choice maybe with the cortex a15 quad or octacore and at least quadcore gpu


Lets skip one revision ;)
 
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