MaVo159
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Future gpu upgrades

Wed Mar 02, 2016 1:21 pm

Dear RasPi team,

Parts of the community had hopes for a gpu upgrade prior to the launch the RasPi3. If I remember correctly the availability of an open driver has been cited as an important motivator to stick with VC4 (which is limited to ancient OpenGl ES 2).
I very much appreciate the preference of openness over graphics performance, as it allows us to run a software stack without all the trouble introduced by binary blobs.

However, the freedreno mesa driver for Adreno 3xx and 4xx gpus has made tremendous progress lately and has long surpassed the capabilities of VC4. It has reached OpenGl ES 3.0 compatibility (only exception atm is MSAA) and is getting closer to supporting OpenGl 3.1 as well. Even OpenGl ES 3.1 features are planned for at least 4xx.

Are you interested in supporting a modern graphics APIs in future iterations?
Given that VC seems to receive no updates... can you imagine using Snapdragon chips with Adreno gpus in future iterations?
Do you have any hope that broadcom can deliver chips that support modern OpenGl with an open driver in the near future?
Last edited by MaVo159 on Wed Mar 02, 2016 3:11 pm, edited 2 times in total.

jamesh
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Re: Future gpu upgrades

Wed Mar 02, 2016 1:49 pm

Firstly, the Foundation future plans are never made public.

My thoughts.

FInding a chip that does everything required, and has a newer up to date GPU, plus is backwards compatible.....difficult if not impossible. The VC4 dev team is disbanded (Broadcom closed down the division making us all redundant) so movement that way is limited. Moving to a new core is a very very very expensive proposition. Going to be interesting to see what the Foundation comes up with.
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MaVo159
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Re: Future gpu upgrades

Wed Mar 02, 2016 3:45 pm

If backwards compatibility is that difficult to achieve with a different chip and Broadcom has no plans for VC, does that mean the foundation is running out of options?

Or is it imaginable that future Raspis will just stick with VC while continuing to upgrade the other components.
I am not very clear on how tightly coupled the individual functional parts are and how interesting/difficult it is for Broadcom to support that.

Anyway, I assume Broadcom wants to move on to modern gpus for other products. Is there any info on what they are going to use (or are using already)? Mali?

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Re: Future gpu upgrades

Wed Mar 02, 2016 3:51 pm

MaVo159 wrote:If backwards compatibility is that difficult to achieve with a different chip and Broadcom has no plans for VC, does that mean the foundation is running out of options?

Or is it imaginable that future Raspis will just stick with VC while continuing to upgrade the other components.
I am not very clear on how tightly coupled the individual functional parts are and how interesting/difficult it is for Broadcom to support that.

Anyway, I assume Broadcom wants to move on to modern gpus for other products. Is there any info on what they are going to use (or are using already)? Mali?
The Raspberry Pi is a VPU with a CPU attached. Most other SoCs available are standard ARM CPU with a GPU.

So as stated ad-infinitum it would take $$$$$$ to undertake a radical change and mean re-writing a shed load of documentation.

RPT will not divulge any future plans.

So bottom line this is no different to the 100's of other posts which end up going nowhere :o
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Re: Future gpu upgrades

Wed Mar 02, 2016 4:00 pm

*secretly hopes for a VC5*
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Re: Future gpu upgrades

Wed Mar 02, 2016 4:12 pm

What about Qualcomm? Most of their SoCs are pretty versatile and they seem to be one of the more open manufacturers. Plus there are Open Source GPU drivers available already.

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Re: Future gpu upgrades

Wed Mar 02, 2016 4:21 pm

ric96 wrote:*secretly hopes for a VC5*
..seems the logical forward path if the "NEW" Broadcom https://en.wikipedia.org/wiki/Broadcom_Limited can be persuaded, though I am sure RPT, as always, have a future plan and will surprise everyone ;)
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Re: Future gpu upgrades

Wed Mar 02, 2016 4:33 pm

fruitoftheloom wrote:
ric96 wrote:*secretly hopes for a VC5*
..seems the logical forward path if the "NEW" Broadcom https://en.wikipedia.org/wiki/Broadcom_Limited can be persuaded, though I am sure RPT, as always, have a future plan and will surprise everyone ;)
Not sure how you persuade all the now Ex-Brcm people who know how to make the VC5 to come back. Lots of the softies now working for some pretty high up companies now (Amazon, Google, Roku etc) with associated pay increases!

Right now I believe the new Broadcom are shedding staff like no tomorrow.
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Re: Future gpu upgrades

Wed Mar 02, 2016 5:07 pm

With Broadcom pulling the plug on development of an essential part of the Raspi I'm voting on a future Raspi being a RSIC V processor. Perhaps that Low RISC being built in Cambridge.

Perhaps with graphics based on the open source MIAOW GPU http://miaowgpu.org/

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Re: Future gpu upgrades

Wed Mar 02, 2016 5:48 pm

jamesh wrote:Not sure how you persuade all the now Ex-Brcm people who know how to make the VC5 to come back.
These aren't the VC5s you're looking for. . . Does any upgrade to the GPU have to be that upgrade? Couldn't there be an incremental upgrade where it is still a VC4 but the things that actually matter for the Pi get improved/shrunk/increased in number? (I am not a hardware engineer but it is an interesting topic).

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Re: Future gpu upgrades

Wed Mar 02, 2016 5:54 pm

Broadcom still retain various members of the old V3D team (both HW & SW) (though I wouldn't care to speculate exactly what it is they're working on).

The real problem is all of the stuff on top of V3D that makes up VideoCore, e.g. the camera stuff. If Broadcom make a new chip with an updated V3D it almost certainly won't include the rest of VideoCore.

Perhaps currently VideoCore + new V3D is an option, but who knows?

Ultimately the pi will want a GPU upgrade at some point. They'll want to retain backwards compatability and avoid major software changes which points towards retaining VideoCore but with improvements. However this requires Broadcom to produce the appropriate chip.

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Re: Future gpu upgrades

Wed Mar 02, 2016 5:57 pm

The problem is the VC4 has been pretty much extended to its maximum capability. One of the big issues that still remain is the 1GB RAM barrier.

My guess:
The Foundation will invest in either getting that VC5 core up and running or hacking up the VC4 architecture to add additional QPUs along with extending the memory barrier. So instead of doing 2 years of new chips like with the 2836 and 2837 (thats a lot of $$$) they will save the money and do the minimum required to extend the life of the current architecture by doing the necessary design and validation for that.

They also have the option of going for a smaller manufacturing process and increasing clock speeds of both CPU and GPU, which I think makes the most sense and is the cheapest option for the time being. Right now the 2837 is a very hot chip in need of some power saving measures and a 40nm to 20nm reduction would be handy for that. Maybe steal some onboard ethernet from other broadcom chipsets while you are at it...

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Re: Future gpu upgrades

Wed Mar 02, 2016 8:34 pm

There are a number of options, all expensive (going to 28nm would be very very expensive). Adding gig ethernet, improving the memory controller, adding USB 3, adding quads (not necessarily an improvement interestingly) etc. All possible, al expensive.

I'm sure Eben is on the case!
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Re: Future gpu upgrades

Wed Mar 02, 2016 8:52 pm

jamesh wrote:There are a number of options, all expensive (going to 28nm would be very very expensive). Adding gig ethernet, improving the memory controller, adding USB 3, adding quads (not necessarily an improvement interestingly) etc. All possible, al expensive.
I am curious though, how on earth did you guys manage to get the 2837 out so quickly? The initial cost of the 2836 was already incredible. If 3 million Pi 2s were sold, each unit would basically have to contribute around a dollar or so just to pay off the R&D on that chip. You guys seem to have bigger margins than I expected, or was Broadcom happy to help out?
jamesh wrote: I'm sure Eben is on the case!
Let me guess, the bcm2838 is currently being validated and soon to be shipped to TSMC :lol:

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Re: Future gpu upgrades

Wed Mar 02, 2016 9:30 pm

bstrobl wrote:
jamesh wrote:There are a number of options, all expensive (going to 28nm would be very very expensive). Adding gig ethernet, improving the memory controller, adding USB 3, adding quads (not necessarily an improvement interestingly) etc. All possible, al expensive.
I am curious though, how on earth did you guys manage to get the 2837 out so quickly? The initial cost of the 2836 was already incredible. If 3 million Pi 2s were sold, each unit would basically have to contribute around a dollar or so just to pay off the R&D on that chip. You guys seem to have bigger margins than I expected, or was Broadcom happy to help out?
jamesh wrote: I'm sure Eben is on the case!
Let me guess, the bcm2838 is currently being validated and soon to be shipped to TSMC :lol:
Let me first say a couple of things
1) I have no knowledge whatsoever about hardware design, rpi foundation plans, graphics gpus.
2) I think this thread should be locked or erased immediately!

Having said that my guesses are as follows:

I think vc4 has long been rather behind as from what I vaguely remember the data bus on vc4 is 128bit and I think mali is 256 and has been for some time, so bandwidth is going to be lacking for a lot of future stuff.

A new chip is unlikely, though people that I believe might know have said the vc5 gpu was complete before the project was dumped, but all the video codec stuff what stalled due to standards and licencing problems with h265.

I have no idea what that means.

I think adding new ARM cores onto the vc4 die is relatively easy thats why broadcom churns them out so quick.

Things that take time would be scaling to a smaller silicone die feature size, redesigning the data bus, adding pipelines for more qpu gpu processors, redsigning the dma system which is very important part of moving large amounts of data around, etc etc etc...

I have no idea about all that, it is way too complex for anyone on this forum and thinking about it will change nothing.

So what I hope is, Broadcom invests in some amazing flexible I/O hardware dma gpio system that can handle shifting out extreamly high speed 10GHz serial data on any and all gpio pins allowing usb 3.1/SDXC UHS2/SDIO on any and every external connection with loads of clock options etc.

Then they need to bump the data bus to 512bits wide stack on 16x more qpu that in the VC4, reduce the die feature size to 14nm and multiply the clock speed by 4, then implement Vulkan and h266 drivers.

Finally when the rpi foundation design the board they need to add a multiprocessing cluster chip stacking interconnect, SD card raid bus for 8 ultra uSD cards, mcu IO coprocessor with multi channel ADC and DAC and shared memory, 32Gb pop memory, and liquid cooling quick connectors.

Now please lock the thread!

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Re: Future gpu upgrades

Wed Mar 02, 2016 9:33 pm

....and a Shetland Pony as an incentive :shock:
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Re: Future gpu upgrades

Wed Mar 02, 2016 9:37 pm

fruitoftheloom wrote:....and a Shetland Pony as an incentive :shock:
You better let Mr. Hands know! :oops:

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Re: Future gpu upgrades

Wed Mar 02, 2016 9:40 pm

mung wrote:I think vc4 has long been rather behind as from what I vaguely remember the data bus on vc4 is 128bit and I think mali is 256 and has been for some time, so bandwidth is going to be lacking for a lot of future stuff.
Yeah, but have you seen how fast VC4 is when overclocked to 500MHz? Nearly all of them will do it now. The yields must be really good after all this practice they've had at making them. :D
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Re: Future gpu upgrades

Wed Mar 02, 2016 9:47 pm

GTR2Fan wrote:
mung wrote:I think vc4 has long been rather behind as from what I vaguely remember the data bus on vc4 is 128bit and I think mali is 256 and has been for some time, so bandwidth is going to be lacking for a lot of future stuff.
Yeah, but have you seen how fast VC4 is when overclocked to 500MHz? Nearly all of them will do it now. The yields must be really good after all this practice they've had at making them. :D
I have been running my pi zero at 1200/600/600 since I got it with no problems except it ruined my SD card :(

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Re: Future gpu upgrades

Thu Mar 03, 2016 9:14 am

bstrobl wrote:
jamesh wrote:There are a number of options, all expensive (going to 28nm would be very very expensive). Adding gig ethernet, improving the memory controller, adding USB 3, adding quads (not necessarily an improvement interestingly) etc. All possible, al expensive.
I am curious though, how on earth did you guys manage to get the 2837 out so quickly? The initial cost of the 2836 was already incredible. If 3 million Pi 2s were sold, each unit would basically have to contribute around a dollar or so just to pay off the R&D on that chip. You guys seem to have bigger margins than I expected, or was Broadcom happy to help out?
jamesh wrote: I'm sure Eben is on the case!
Let me guess, the bcm2838 is currently being validated and soon to be shipped to TSMC :lol:
Changing the ARM cores is the 'easy' part, so can be done pretty quickly, and the Foundation supplied an engineer to help (James IIRC, or was that 2836?).

I've not heard of a 2838. But I don't work for the Foundation or BRCM.
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Re: Future gpu upgrades

Thu Mar 03, 2016 9:28 am

You'd `ve thought there'd be a chip in the Broadcom set-top box portfolio (thinking ultra HD) that may offer an upgrade on the GPU side, though not sure about the CPUs they offer.

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Re: Future gpu upgrades

Thu Mar 03, 2016 9:42 am

There may well be, however such a chip wouldn't include VideoCore (other than the V3D part).

Obviously it'd have video decode/display, but it'd be totally different technology to the Pi decode/display, so major SW changes required. Doubtful it would have any kind of camera functionality too.

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Re: Future gpu upgrades

Thu Mar 03, 2016 9:58 am

Ah yes I'd forgotten about the camera & display ports, rules that out then.

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Re: Future gpu upgrades

Thu Mar 03, 2016 10:53 am

couldn't they just use a completely new SOC and put the old one onto the board too for backward compatibility? :) that would be cool. :)

isn't this what they did with the playstation 2? it contained the complete playstation 1 hardware.

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Re: Future gpu upgrades

Thu Mar 03, 2016 10:59 am

MaVo159 wrote:Or is it imaginable that future Raspis will just stick with VC while continuing to upgrade the other components.
It is to me, but it equally wouldn't surprise me if the Foundation pulled something out of the bag.

For a platform designed to teach coding and computer science there is little requirement for ultra high performance graphics, but the Pi has become much more than just that, and it will need to remain competitive against newcomers to continue generating revenue to fund the Foundation's missions.

The Pi may ( probably will ) lose ground to some alternatives in the future but it should still be able to hold its own in the market it is targeted at, and particularly as its success is about much more than just hardware.

Put bluntly; the Pi doesn't have to be the lead horse. There's noting wrong, and no shame, in being a bicycle manufacturer in a sea of car and super car manufacturers.

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