alberich2k5
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Arm and SOC

Mon Dec 30, 2013 10:41 am

Hello!

I know this may sound naive question, but this came out to my mind some days ago while looking for information about arm soc model at my rpi. I couldn't find anything related to the chip, but from this forums.
I was thinking this was kind of similar to PC world, where you can buy the chip (in this case the soc already built, we are talking about the rpi but we can extend it to general arm soc I think). If I want to buy an arm soc,an already designed one as I don't know how to do it, where can I buy/order it? or in other words, are all arm socs custom designed/integrated? How does this works?

thanks in advance,
Alberich

Ravenous
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Re: Arm and SOC

Mon Dec 30, 2013 10:51 am

You can't get them separately, you could probably get them if you had a business use in mind and went to the maker with plans for, perhaps, 100,000 units!

Apparently the SoC was designed for a particular device in mind, and later the raspi was based on the same chip because it was cheap and happened to have most of what the raspi designers wanted.

There have been a few interesting business discussions on the forum (doubt we'll be able to find them now) about how many of these chips are designed with just one or two phones in mind. It's been said that in this case the SoC is really a graphics chip and just happens to have an ARM device that was built in, almost as an afterthought!

jdb
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Re: Arm and SOC

Mon Dec 30, 2013 11:06 am

ARM processors are not sold separately (in every sense of the word).

ARM holdings, the company that owns the IP for all ARM processors, licences the designs out to companies for a fee. The companies with a licence can then put the various processors into chips, usually designed-in to a system-on-chip which will have various peripherals, buses, interconnects specific for the application. The usual arrangement is to have an entire chip made specific for that application, which means you can buy in quantities of >100,000.

The ARM cpu core inside BCM2835 is the ARM1176JZF-S. As another example, I have a DNS-320L at home which has a Marvell Kirkwood SoC inside. That chip has 2 DMA engines with XOR capability (for hardware RAID), 2 SATA 3GBPS interfaces, a DDR2 controller, a basic i2c and GPIO block, 1-port USB2.0 (EHCI) interface and an onboard gigabit ethernet interface. The CPU itself is a fairly weedy (modified) ARMv5TE.This is because the SoC was specifically designed as a NAS chip.
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alberich2k5
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Re: Arm and SOC

Mon Dec 30, 2013 11:56 am

Let's say i want to build a NAS, similar to the d-link you mentioned. There's no way to find public available arm socs? So I can see if they can be suitable for my board or choose the closer one if I want to save the development of the SoC, even if I have to buy >100.000 units for a board.

I'm using the NAS as an example. You can put any other application/board.

Thank you very much

dave j
Posts: 117
Joined: Mon Mar 05, 2012 2:19 pm

Re: Arm and SOC

Mon Dec 30, 2013 2:08 pm

alberich2k5 wrote:Let's say i want to build a NAS, similar to the d-link you mentioned. There's no way to find public available arm socs? So I can see if they can be suitable for my board or choose the closer one if I want to save the development of the SoC, even if I have to buy >100.000 units for a board.

I'm using the NAS as an example. You can put any other application/board.

Thank you very much
You can sometimes find information about ARM SoCs from manufacturers web sites. e.g. You can find details of the Marvell Kirkwood SoC jdb mentioned. Other manufacturers have different levels of information easily available on their web sites.

jamesh
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Re: Arm and SOC

Mon Dec 30, 2013 2:30 pm

alberich2k5 wrote:Let's say i want to build a NAS, similar to the d-link you mentioned. There's no way to find public available arm socs? So I can see if they can be suitable for my board or choose the closer one if I want to save the development of the SoC, even if I have to buy >100.000 units for a board.

I'm using the NAS as an example. You can put any other application/board.

Thank you very much
I'd guess that a custom ARM based chip would be quite a few million $ to develop. So unless you have a high volume product in mind, you are going to need to buy an existing chip. And that's where the problem is - finding an appropriate one. You'll need to trawl the manufacturers of SoC's websites for the different devices available - Wikipedia may have a list of manufacturers.
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jdb
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Re: Arm and SOC

Mon Dec 30, 2013 4:47 pm

While that may have been true until a few years ago, Cortex M-series processors are now making their way into semi-affordable microcontroller-type applications. They are specifically microcontroller-based though - limited instruction set, 3-stage pipeline which limits the computational power to not a lot.

http://www.ti.com/lsds/ti/arm/arm_corte ... rview.page
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jamesh
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Re: Arm and SOC

Mon Dec 30, 2013 5:06 pm

jdb wrote:While that may have been true until a few years ago, Cortex M-series processors are now making their way into semi-affordable microcontroller-type applications. They are specifically microcontroller-based though - limited instruction set, 3-stage pipeline which limits the computational power to not a lot.

http://www.ti.com/lsds/ti/arm/arm_corte ... rview.page
Good point.
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Heater
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Re: Arm and SOC

Mon Dec 30, 2013 5:54 pm

Depends what you want in you SoC.

Digi-key have about 350 different SoCs in their catalog.

alberich2k5
Posts: 11
Joined: Wed Jun 27, 2012 9:42 am

Re: Arm and SOC

Tue Dec 31, 2013 8:47 am

Now I see.
Thank you very much for your replies.

Heater, I don't want to build anything. Just curious about how things work on arm world. Also, I'm from computer science so I don't trust myself to build boards, only to program them :D

Thank you very much guys for the replies,
happy new year

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