Qualcomm Says Eight-Core Processors Are Dumb

itwbennett writes "Following rival MediaTek's announcement of plans to release an eight-core processor in the fourth quarter, Qualcomm has declared eight-core processors 'dumb'. 'You can't take eight lawnmower engines, put them together and now claim you have an eight-cylinder Ferrari. It just doesn't make sense,' Qualcomm's senior vice president Anand Chandrasekher said, according to a transcript of his comments to Taiwan media provided on Friday. Asked whether Qualcomm would one day launch its own octa-core processor, Chandrasekher said, 'We don't do dumb things.'"

Comments

Re:qualcomm is right

[Samantha Wright]

I'm somewhat inclined to agree, actually! Samsung's S4 uses different cores running at different clock speeds for different tasks, and is obviously about improving power utilization. Given that, it really just looks like Qualcomm is trying to spin their business decision (to not do eight-core chips, probably because they don't think they can compete) to their investors as cost-saving for their customers. I didn't get the impression that power consumption was the bigger concern. But, hey, maybe that's their niche.

I'll say it

[fyngyrz]

You know what multiple cores are great for, that a very large segment of the population does? Image processing. A very large subset of things you can do to images responds very well to slicing an image into [#ofCores] slices, and then whacking away at them in [#ofCores] parallel.

I write SDR software, that kind of programming can really benefit from multicore hardware too. At least, the way I write it, it does.

Anyway, I think ol Qualcomm is lacking a certain basic understanding of what multicore architecture brings to the table. Er, phone. Desktop. Tablet. Whatever.

But that's ok. Manufacturers that remain mired in the past fall to their competitors and so self-select themselves out of the game.

Re:I'll say it

[tlhIngan]

Anyway, I think ol Qualcomm is lacking a certain basic understanding of what multicore architecture brings to the table. Er, phone. Desktop. Tablet. Whatever.

But that's ok. Manufacturers that remain mired in the past fall to their competitors and so self-select themselves out of the game.

Except Qualcomm has a point.

An 8 core SoC has 4 powerful A15-ish cores, and 4 power efficient A7-ish cores. Now, ARM's big.LITTLE allows for OS awareness of all 8 cores and their asymmetry, or you can treat it as a 4-core system and perform a direct switch.

The reason for this is the A15 is a power hog. It's fast, but it turns energy into heat very quickly. The A7 is slower, but turns less energy into heat. When you're gaming, you want the big beefy cores to give you maximum FPS goodness or whatever, then when you're back to listening ot MP3s, switch it for the power sippers.

Now, Qualcomm has skin in the game in that their 4 core Kraits are able to do DVFS on each individual core (so each core runs as fast as it needs to be, and no faster), which means it doesn't need a secondary batch of slower processors because it can run the main ones slower and more power efficiently..

Of course, what 8-core purveyors DON'T mention is you cannot run all 4 A15 cores for more than a few minutes at a time - you'll destroy the SoC because it overheats. That's how bad the A15s are. If you can use 2 A15s and keep the other 2 idle, for the most pare, you can do this forever. But put some load in and you'll need to throttle the A15s - 100-100-50-50% at first, and if temperatures still aren't cooling, start throttling the slower ones even more, turning them off if need be.

And in phones there's no space for the heatsink and fan, and often there's a PoP memory on top, so you can't even stick a heatsink on if you wanted.

Thermal management is extremely important on these octacores. especially as the system can't be cooled traditionally.

Until Qualcomm makes a server chip, they do have a point - what's the point of quad or octacore if you're not able to keep them running at full load because the hardware is limiting the speed?

Of course, anyone will know that benchmarks only run for a few minutes at a time. Aggressive core management also helps (switching to A7s as much as possible to keep the chip cooler).

Re:The Onion said it best

[Anonymous Coward]

On the other hand, Qualcomm is probably saying 8-cores is stupid, because they don't have one on the market. Wait to hear what they say when they come up with one.

No, they're saying they're stupid because they really are stupid. There is little demand for more than 2 cores in today's (or tomorrow's) mobile software. 2 cores is the sweet spot, 4 is questionable, 8 is brazenly pandering to people who have no clue.

The other thing is that the Samsung chip isn't even a genuine 8-core device. To be sure, there are a total of eight physical ARM cores present, but by design you're only intended to use four at a time. There are two clusters of four cores. One is a Cortex-A15 cluster (fast, high power, occupies lots of die area), the other is Cortex-A7 (slow, low power, small). This is a concept that ARM Holdings markets as "big.LITTLE". They don't have any core designs with a sufficiently wide dynamic range of power/performance operating points, so they're compensating by telling customers (like Samsung) that they should design in a redundant set of cores of a different design which can reach the desired power consumption targets. Firmware running below the OS decides which cluster should be active at any given time, and manages handoffs and powerdown of the inactive cluster. It's a very inelegant kludge, especially since the handoffs cause performance hits.

Qualcomm and Apple both have high performance homegrown ARM core designs which scale down to lower power states better than A15, though they're not quite as fast as A15 on the top end. Hence, both of them are offering dual-core parts, since as long as your individual cores are fast two, is pretty much enough for the vast majority of mobile software. Apple is particularly focused on maximizing performance to power ratio, since they focus exclusively on building small (no 5" screens), thin, and light phones, yet they still want to be close to the top in real world performance and also among the best in battery life.

Both of them could be shipping 4+ cores right now if they thought it was worth it. Once you've gone to two cores, adding more is fairly simple, since all the mechanisms for maintaining cache coherency between multiple cores have already been worked out. But they don't think it's worth it so they haven't done it.

Samsung, on the other hand, needs something to hang their hat on. Unlike Qualcomm they can't integrate radios into their SoCs (yet, but they're working on it), which is a huge disadvantage. And they don't (yet, but they're working on it) have their own custom ARM core design. So they're trying to differentiate their current products using the hand they've been dealt, which presently means using ARM's big.LITTLE concept to offer absurd core counts that aren't actually useful to end users, and a bunch of other questionable things.