5 ms·

That's really a surprise. Broadcom is cemented in my mind as one of the hardest companies to get even basic datasheets out of. I know the saying is "don't look

That's really a surprise. Broadcom is cemented in my mind as one of the hardest companies to get even basic datasheets out of. I know the saying is "don't look a gift horse in the mouth", but could it be that their graphics cores are not competitive in pure technical capabilities, so they've decided to compete on open-ness? I'm not really involved in that area of hardware/software.

ebenupton 13y ago
Nope (though note, I'm biased for several reasons). In terms of performance per unit area and performance per Watt, VideoCore IV is about as good as you're going to get. There are chips with higher performance GPUs out there, but they get there by brute force: throwing area (and therefore cost) and/or power at the problem.
- stingraycharles 13y ago
  This is confirmed by the recent move of AMD towards extremely hot GPUs. You already see that in the most recent 290x, but they're talking about making hardware that is comfortable running at >100C. I'm not sure how relevant that is with regards to performance per watt, but I do know that heat is one of the most expensive (by-)products of electricity.
  - wtallis 13y ago
    That's not really relevant. Broadcom's VideoCore competes against the likes of PowerVR, ARM's Mali, and Qualcomm's Adreno. Those GPUs are all designed for mobile use, and cannot easily scale up to compete with desktop/workstation-class GPUs due to architectural differences and fab process differences. AMD's chips aren't egregiously power-hungry, they just sell into a market where the product segments are defined by the thermal and electrical limitations of the PCIe expansion card form factor. It will always be the case that the top of the line card draws as much power as can be delivered through the slot and two extra connectors, and as much as can be dissipated through a two-slot cooling system. If AMD can safely operate their chips at a higher temperature, then their cooling system will be a bit more efficient, so their thermal envelope expands a bit and they can increase performance by a few percent. Early indications are that NVidia's upcoming Maxwell architecture achieves significant efficiency improvements due to being designed with mobile use in mind, but it hasn't yet been demonstrated in a large enough configuration to compare against high-end desktop graphics chips.
    - stingraycharles 13y ago
      I stand corrected.
  - csense 13y ago
    Isn't there some theorem of thermodynamics that says your device gets more efficient as the temperature difference between the hot and cold parts of the device increases? AFAIK the only reasons devices aren't run at arbitrarily high temperatures is that material properties change unfavorably, or you risk fires.
    - wtallis 13y ago
      The efficiency thing is more about heat engines. When we're just dissipating heat, the relevant relationship is that the rate of heat transfer is proportional to the temperature difference. This is why a hot object that isn't producing heat will cool exponentially. In the case of a steady-state source of heat, the temperature difference will be inversely proportional to the thermal conductivity of the connection between hot and cold reservoirs. Heatsinks and fans are used to increase that thermal conductivity so that the temperature difference stays small enough that the absolute temperature is safe. If you can double the tolerable temperature difference, then you can cut your fan speeds by more than half, or even get by with passive convection. Or, approaching things differently, if you're only going to keep your graphics card for two or three years, there's no reason to let the fans spin up to an audible level until the chip reaches at least 80 degrees C. Addressing a common misconception: fan speed/noise is not directly related to how much the graphics card is heating up the room by. Whether you run the fans at full tilt or you let the chip almost melt, the heat output will depend only on the workload.
    - tryp 13y ago
      The thermodynamics you are remembering mostly refers to Carnot engines which convert temperature differences to work.
  - Perdition 13y ago
    I just switched my GPU to an nVidia GTX 750 for precisely this reason. I have been near exclusively using Radeons for ten years, but the last few generations just run too hot and loud.
- AceJohnny2 13y ago
  Two years ago (or whenever the BCM2835 itself came out on the market), sure, but surely things have improved since? We've at least jumped a technology node, and hasn't nVidia improved?
  - ebenupton 13y ago
    Less than you'd think. Other vendors have improved somewhat, but from often from pretty poor starting points. Jumping a process node is a "brute force" approach: we can all do that. I'm more interested in apples-to-apples comparisons on a given node.
    - AceJohnny2 13y ago
      Had you worked on it directly, or were working on other parts of the chip while at Broadcom? I've always been hoping to see some hard benchmarks. I had worked on a video codec IP for a competing (but defunct) chip, hence my curiosity :) I'm curious about the technological history of the VideoCore. The wikipedia page [1] and Broadcom marketing page [2] don't give a lot of information to distinguish it from competing cores (such as ARM's own Mali or nVidia's Tegra line). In fact, the information I see makes it seems pretty run-of-the-mill tech of 5 years ago. I guess I could RTFM now that it's available :D Edit/afterthought: none of this really matters actually, as there is no other chip on the market with the BCM2835's capabilities and that is more open-sourced. [1] http://en.wikipedia.org/wiki/VideoCore http://en.wikipedia.org/wiki/VideoCore [2] http://www.broadcom.com/products/technology/mobmm_videocore.php http://www.broadcom.com/products/technology/mobmm_videocore....
      - ebenupton 13y ago
        I did work on it directly. James (now working solely for Pi as HW director), Gordon (now working solely for Pi as SW director) and I (still working for Broadcom, and for Pi) were members of the VideoCore IV design team. James and I were responsible for the QPU (quad processor unit) design and implementation in the V3D block. There's no one thing about V3D which makes it superior to other cores. Just lots of attention to detail at the design, RTL implementation and layout stages.
- xamlhacker 13y ago
  Waiting for the VideoCore V :) I noticed that the Broadcom LTE offerings such as the M320 do not use VideoCore and instead use PowerVR 5XT. Is it because they were originally Renesas designs? Hoping to see more VideoCore action in the future :)
  - ebenupton 13y ago
    :)
akiselev 13y ago
Looking at the long term future of the market, Broadcom's move isn't surprising at all. Broadcom (and Qualcomm for that matter) is feeling a lot of pressure from Intel and NVidia, both of whom have a lot of new stuff that are scaring competitors (which is fucking great for us). They're scared not from just a technological or capital/market perspective, but also from a community exposure one. They're both firing on all cylinders right now improving their technology and trying to get as many engineers to use it as possible. While firmware engineers tend to be older, there is a constant cycle and the industry is starting to see the importance of open source, especially as die complexity grows and more and more testing is required for each silicon design. Intel: 2.5W TDP quad core Atoms with Intel's x86 instruction pipeline and memory management unit have been released as well as a low cost SDR that should be able to dynamically switch between unlicensed, GSM, CDMA, and LTE spectrum. Intel's graphics work is also quickly catching up and will soon start trickling into their low power embedded chips. Intel has also made clear moves with Galileo to open up their technology to the hobbyist engineers. NVIDIA: The Tegra K1 is out to NVIDIA's partners (supposedly it beats VideoCore and even low end integrated desktop graphics) and they are currently being worked into tablets. NVIDIA also has recently released the i500, their own software defined radio to compete with Intel, and both companies have the resources to end the lock-in that Qualcomm and Broadcom have had in their respective baseband markets. If you're already buying radios from them, it makes sense to get your processor from them too and Broadcom may be trying to hedge against that. NVIDIA (and maybe Intel) aren't known to be pioneers of open source but they're better than most other Silicon companies and everyone else is really starting to feel the pressure. The problem of supporting many different device configurations is an old one on desktop systems and that problem is only magnified 10x for embedded engineers because of the opacity. With Intel and NVIDIAs expertise on the desktop as they're running full steam ahead into embedded (and kicking ass along the way), they're scary to the old guard.
- zanny 13y ago
  > NVIDIA (and maybe Intel) Intel has a huge workforce dedicated to open source. They fund huge chunks of kernel, Wayland, X and Mesa development, and I'm sure they have engineers on projects throughout the foss stack. Yeah, their hardware is pretty systemically evil patent drivel black box nonsense, and their chipsets are some of the most obscure bullshit ever, but everything past the firmware they do a good job on. Nvidia on the other hand consistently blows whole stack. Their foss Tegra drivers are always, at most, 2d accelerated, and all their recent contributions to Nouveau (all two of them) are just to make SoCs bootable on novueau so you can install their blob driver. Meanwhile, technologies like CUDA, GSYNC, PHYSX, etc are all proprietary platform locked messes that hurt open tech in general. So I'd definitely rank them way below Intel on a comparison of openness.
pjc50 13y ago
This is almost certainly driven entirely by Eben Upton, who is the link between Broadcom and Raspberry Pi. He's probably been bundling up the huge list of demands for OSS video drivers and dumping them on the desk of the right person, while wearing down the objectors. It's something that Raspberry Pi have wanted for ages. Edit: ah, Eben has turned up here himself :)

ebenupton 13y ago

Nope (though note, I'm biased for several reasons). In terms of performance per unit area and performance per Watt, VideoCore IV is about as good as you're going to get. There are chips with higher performance GPUs out there, but they get there by brute force: throwing area (and therefore cost) and/or power at the problem.

stingraycharles 13y ago
This is confirmed by the recent move of AMD towards extremely hot GPUs. You already see that in the most recent 290x, but they're talking about making hardware that is comfortable running at >100C. I'm not sure how relevant that is with regards to performance per watt, but I do know that heat is one of the most expensive (by-)products of electricity.
- wtallis 13y ago
  That's not really relevant. Broadcom's VideoCore competes against the likes of PowerVR, ARM's Mali, and Qualcomm's Adreno. Those GPUs are all designed for mobile use, and cannot easily scale up to compete with desktop/workstation-class GPUs due to architectural differences and fab process differences. AMD's chips aren't egregiously power-hungry, they just sell into a market where the product segments are defined by the thermal and electrical limitations of the PCIe expansion card form factor. It will always be the case that the top of the line card draws as much power as can be delivered through the slot and two extra connectors, and as much as can be dissipated through a two-slot cooling system. If AMD can safely operate their chips at a higher temperature, then their cooling system will be a bit more efficient, so their thermal envelope expands a bit and they can increase performance by a few percent. Early indications are that NVidia's upcoming Maxwell architecture achieves significant efficiency improvements due to being designed with mobile use in mind, but it hasn't yet been demonstrated in a large enough configuration to compare against high-end desktop graphics chips.
  - stingraycharles 13y ago
    I stand corrected.
- csense 13y ago
  Isn't there some theorem of thermodynamics that says your device gets more efficient as the temperature difference between the hot and cold parts of the device increases? AFAIK the only reasons devices aren't run at arbitrarily high temperatures is that material properties change unfavorably, or you risk fires.
  - wtallis 13y ago
    The efficiency thing is more about heat engines. When we're just dissipating heat, the relevant relationship is that the rate of heat transfer is proportional to the temperature difference. This is why a hot object that isn't producing heat will cool exponentially. In the case of a steady-state source of heat, the temperature difference will be inversely proportional to the thermal conductivity of the connection between hot and cold reservoirs. Heatsinks and fans are used to increase that thermal conductivity so that the temperature difference stays small enough that the absolute temperature is safe. If you can double the tolerable temperature difference, then you can cut your fan speeds by more than half, or even get by with passive convection. Or, approaching things differently, if you're only going to keep your graphics card for two or three years, there's no reason to let the fans spin up to an audible level until the chip reaches at least 80 degrees C. Addressing a common misconception: fan speed/noise is not directly related to how much the graphics card is heating up the room by. Whether you run the fans at full tilt or you let the chip almost melt, the heat output will depend only on the workload.
  - tryp 13y ago
    The thermodynamics you are remembering mostly refers to Carnot engines which convert temperature differences to work.
- Perdition 13y ago
  I just switched my GPU to an nVidia GTX 750 for precisely this reason. I have been near exclusively using Radeons for ten years, but the last few generations just run too hot and loud.
AceJohnny2 13y ago
Two years ago (or whenever the BCM2835 itself came out on the market), sure, but surely things have improved since? We've at least jumped a technology node, and hasn't nVidia improved?
- ebenupton 13y ago
  Less than you'd think. Other vendors have improved somewhat, but from often from pretty poor starting points. Jumping a process node is a "brute force" approach: we can all do that. I'm more interested in apples-to-apples comparisons on a given node.
  - AceJohnny2 13y ago
    Had you worked on it directly, or were working on other parts of the chip while at Broadcom? I've always been hoping to see some hard benchmarks. I had worked on a video codec IP for a competing (but defunct) chip, hence my curiosity :) I'm curious about the technological history of the VideoCore. The wikipedia page [1] and Broadcom marketing page [2] don't give a lot of information to distinguish it from competing cores (such as ARM's own Mali or nVidia's Tegra line). In fact, the information I see makes it seems pretty run-of-the-mill tech of 5 years ago. I guess I could RTFM now that it's available :D Edit/afterthought: none of this really matters actually, as there is no other chip on the market with the BCM2835's capabilities and that is more open-sourced. [1] http://en.wikipedia.org/wiki/VideoCore http://en.wikipedia.org/wiki/VideoCore [2] http://www.broadcom.com/products/technology/mobmm_videocore.php http://www.broadcom.com/products/technology/mobmm_videocore....
    - ebenupton 13y ago
      I did work on it directly. James (now working solely for Pi as HW director), Gordon (now working solely for Pi as SW director) and I (still working for Broadcom, and for Pi) were members of the VideoCore IV design team. James and I were responsible for the QPU (quad processor unit) design and implementation in the V3D block. There's no one thing about V3D which makes it superior to other cores. Just lots of attention to detail at the design, RTL implementation and layout stages.
xamlhacker 13y ago
Waiting for the VideoCore V :) I noticed that the Broadcom LTE offerings such as the M320 do not use VideoCore and instead use PowerVR 5XT. Is it because they were originally Renesas designs? Hoping to see more VideoCore action in the future :)
- ebenupton 13y ago
  :)

akiselev 13y ago

Looking at the long term future of the market, Broadcom's move isn't surprising at all. Broadcom (and Qualcomm for that matter) is feeling a lot of pressure from Intel and NVidia, both of whom have a lot of new stuff that are scaring competitors (which is fucking great for us). They're scared not from just a technological or capital/market perspective, but also from a community exposure one. They're both firing on all cylinders right now improving their technology and trying to get as many engineers to use it as possible. While firmware engineers tend to be older, there is a constant cycle and the industry is starting to see the importance of open source, especially as die complexity grows and more and more testing is required for each silicon design. Intel: 2.5W TDP quad core Atoms with Intel's x86 instruction pipeline and memory management unit have been released as well as a low cost SDR that should be able to dynamically switch between unlicensed, GSM, CDMA, and LTE spectrum. Intel's graphics work is also quickly catching up and will soon start trickling into their low power embedded chips. Intel has also made clear moves with Galileo to open up their technology to the hobbyist engineers. NVIDIA: The Tegra K1 is out to NVIDIA's partners (supposedly it beats VideoCore and even low end integrated desktop graphics) and they are currently being worked into tablets. NVIDIA also has recently released the i500, their own software defined radio to compete with Intel, and both companies have the resources to end the lock-in that Qualcomm and Broadcom have had in their respective baseband markets. If you're already buying radios from them, it makes sense to get your processor from them too and Broadcom may be trying to hedge against that. NVIDIA (and maybe Intel) aren't known to be pioneers of open source but they're better than most other Silicon companies and everyone else is really starting to feel the pressure. The problem of supporting many different device configurations is an old one on desktop systems and that problem is only magnified 10x for embedded engineers because of the opacity. With Intel and NVIDIAs expertise on the desktop as they're running full steam ahead into embedded (and kicking ass along the way), they're scary to the old guard.

zanny 13y ago
> NVIDIA (and maybe Intel) Intel has a huge workforce dedicated to open source. They fund huge chunks of kernel, Wayland, X and Mesa development, and I'm sure they have engineers on projects throughout the foss stack. Yeah, their hardware is pretty systemically evil patent drivel black box nonsense, and their chipsets are some of the most obscure bullshit ever, but everything past the firmware they do a good job on. Nvidia on the other hand consistently blows whole stack. Their foss Tegra drivers are always, at most, 2d accelerated, and all their recent contributions to Nouveau (all two of them) are just to make SoCs bootable on novueau so you can install their blob driver. Meanwhile, technologies like CUDA, GSYNC, PHYSX, etc are all proprietary platform locked messes that hurt open tech in general. So I'd definitely rank them way below Intel on a comparison of openness.

pjc50 13y ago

This is almost certainly driven entirely by Eben Upton, who is the link between Broadcom and Raspberry Pi. He's probably been bundling up the huge list of demands for OSS video drivers and dumping them on the desk of the right person, while wearing down the objectors. It's something that Raspberry Pi have wanted for ages. Edit: ah, Eben has turned up here himself :)