Does anyone get 8 CPUs listed?

yahoo2016 · December 19, 2015, 6:43pm

I tried “more /proc/cpuinfo” but got only 4 CPUs listed:

ubuntu@tegra-ubuntu:~$ more /proc/cpuinfo
Processor	: Cortex A57 Processor rev 1 (aarch64)
processor	: 0
processor	: 1
processor	: 2
processor	: 3
Features	: fp asimd aes pmull sha1 sha2 crc32 wp half thumb fastmult vfp 
edsp neon vfpv3 tlsi vfpv4 idiva idivt 
CPU implementer	: 0x41
CPU architecture: 8
CPU variant	: 0x1
CPU part	: 0xd07
CPU revision	: 1

linuxdev · December 19, 2015, 6:55pm

This is all that should be listed. You’ve probably read about the A53 cores, but this is part of the low power mode.

The ARM CPUs tend to advertise the term “big.LITTLE”…which is a way to have both low power and high power without running out of battery. In essense, the A57 cores each have a “shadow” core…the shadow cores are extremely low power and great for detecting activity and then switching back to the A57 cores. The hardware in some computer architectures would require the operating system to glue these CPU cores together…big.LITTLE does this in hardware. Those “LITTLE” cores directly connect to some of the internals of the “big” cores, and do not have issues with software requirements to go back and forth between cores without programming support. Thus, they are invisible, and participate as something of a back end for the fast cores, while the fast cores are the front end. You can’t stop processing to save power…if you did, then you can’t wake up and do things like monitor for an incoming telephone call…A53 can do this with virtually no battery consumption.

There is also an ARM Cortex A9 in TX1, it is a dedicated audio processing core, and will not show up as a CPU.

yahoo2016 · December 19, 2015, 7:35pm

This is all that should be listed. You’ve probably read about the A53 cores, but this is part of the low power mode.

The ARM CPUs tend to advertise the term “big.LITTLE”…which is a way to have both low power and high power without running out of battery. In essense, the A57 cores each have a “shadow” core…the shadow cores are extremely low power and great for detecting activity and then switching back to the A57 cores. The hardware in some computer architectures would require the operating system to glue these CPU cores together…big.LITTLE does this in hardware. Those “LITTLE” cores directly connect to some of the internals of the “big” cores, and do not have issues with software requirements to go back and forth between cores without programming support. Thus, they are invisible, and participate as something of a back end for the fast cores, while the fast cores are the front end. You can’t stop processing to save power…if you did, then you can’t wake up and do things like monitor for an incoming telephone call…A53 can do this with virtually no battery consumption.

There is also an ARM Cortex A9 in TX1, it is a dedicated audio processing core, and will not show up as a CPU.

Thanks for clarification.

crnkoj · December 20, 2015, 10:33am

This is all that should be listed. You’ve probably read about the A53 cores, but this is part of the low power mode.

The ARM CPUs tend to advertise the term “big.LITTLE”…which is a way to have both low power and high power without running out of battery. In essense, the A57 cores each have a “shadow” core…the shadow cores are extremely low power and great for detecting activity and then switching back to the A57 cores. The hardware in some computer architectures would require the operating system to glue these CPU cores together…big.LITTLE does this in hardware. Those “LITTLE” cores directly connect to some of the internals of the “big” cores, and do not have issues with software requirements to go back and forth between cores without programming support. Thus, they are invisible, and participate as something of a back end for the fast cores, while the fast cores are the front end. You can’t stop processing to save power…if you did, then you can’t wake up and do things like monitor for an incoming telephone call…A53 can do this with virtually no battery consumption.

There is also an ARM Cortex A9 in TX1, it is a dedicated audio processing core, and will not show up as a CPU.

I was under the impression that it used heterogeneous multiprocessing, hence that all 8 (4x a53, 4 a57) cores are accessible and usable by the kernel/os at the same time.

dusty_nv · December 20, 2015, 2:30pm

To try and avoid confusion, we advertised Jetson TX1 as featuring “quad-core ARM A57”. To my knowledge NVIDIA didn’t list as 8-core, sorry :(
To confirm, here are a few spec listings:

https://developer.nvidia.com/embedded/buy/jetson-tx1-devkit
http://developer.nvidia.com/embedded/dlc/jetson-tx1-module-data-sheet
http://devblogs.nvidia.com/parallelforall/nvidia-jetson-tx1-supercomputer-on-module-drives-next-wave-of-autonomous-machines/

yahoo2016 · December 20, 2015, 11:41pm

Do Jetson TX1s use the same Tegra X1 chips listed in the following link:

http://www.nvidia.com/object/tegra-x1-processor.html

or they use different version of X1 with only 4 CPUs?

linuxdev · December 21, 2015, 1:08am

Keep in mind that CPU listing in the O/S is only for general purpose CPU. I believe your 8-CPU link is correct, and so is the 4-CPU listing…it’s a case of categorizing. A53 cores shadow the main cores; there is also an A9 core in the audio processor. There are registers for power consumption settings, the O/S itself does not need to bind the A53 and A57 cores together. Perhaps there is a way to access those cores separately, but the general tendency for ARM designs over the last several years has been to make it easy to deal with low power modes without having to take into account each detail of going into or out of low power mode.

yahoo2016 · December 21, 2015, 3:43pm

Do Jetson TX1s use the same Tegra X1 chips listed in the following link:

Embedded Systems Developer Kits & Modules from NVIDIA Jetson

or they use different version of X1 with only 4 CPUs?

Keep in mind that CPU listing in the O/S is only for general purpose CPU. I believe your 8-CPU link is correct, and so is the 4-CPU listing…it’s a case of categorizing. A53 cores shadow the main cores; there is also an A9 core in the audio processor. There are registers for power consumption settings, the O/S itself does not need to bind the A53 and A57 cores together. Perhaps there is a way to access those cores separately, but the general tendency for ARM designs over the last several years has been to make it easy to deal with low power modes without having to take into account each detail of going into or out of low power mode.

As long as the X1 chips on TX1 modules are the same as in Embedded Systems Developer Kits & Modules from NVIDIA Jetson

we can worry about software later.

I hope there is a way to tell how many CPU cores in X1 chip.

dusty_nv · December 21, 2015, 9:11pm

There are 4 CPU cores that you can use simultaneously