Comment by johnklos | Hacker News Reader

Comment by johnklos | Hacker News Reader

"The processor on Ingenuity is 100 times more powerful than everything JPL has sent into deep space, combined."

I think that's a bit exaggerated. The RAD750, which has been used for all sorts of devices, runs from 110 to 200 MHz, typically. A Snapdragon 801 is a quad core 32 bit CPU that can run up to 2.36 GHz. Even if the Snapdragon's IPC is twice that of the PowerPC, even if the Snapdragon is run at its full clock speed (which it certainly is not), and even if the comparison was with the slowest 110 MHz clock of the RAD750, that'd be a factor of 172 times faster.

I think that the person saying this is comparing the floating point throughput of the RAD750 and other CPUs sent in to space with the floating point throughput of the Adreno GPU built in to the Snapdragon 801. That's both misleading and not how things work. But I suppose it makes for catchy headlines, even if it's not factually correct.

Snapdragon also has SIMD instructions (NEON) which can bring 2x-16x performance improvement depending on the algorithm.

I'm no expert, but I think more than these things go into it (and I suspect way more than a 2x IPC bump, but that's guesswork). Also more cache and I'm sure more and faster memory.

The point I was making is that even if one assumes the worst about the PowerPC and the best about the Snapdragon, the comparison doesn't make any sense.

Even if the IPC were FOUR times that of the PowerPC and we accepted the other assumptions in favor of the Snapdragon, that'd make one quad core Snapdragon 344 times faster than the slowest RAD750, so if four or more RAD750s have ever been sent to space, then that'd make the Snapdragon LESS than 100 times faster than just four RAD750s. That's not taking in to account all of the other CPUs used in space missions.

Larger caches and faster memory are necessary to just maintain the IPC - they don't mean that the Snapdragon is faster per clock by virtue of those alone.

I have a 600 MHz PowerPC 750 system (original iMac with Sonnet accelerator) and a Cortex-A15 system (the Cortex-A15 is a 32 bit ARM from around the same time as the Snapdragon 801, and which has better IPC than the Snapdragon), and I can say that the IPC of the Cortex-A15 is much closer to 1.5 times than 2 times that of the PowerPC.

Reply on news.ycombinator.com