gtechn
Posts: 156
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GPU Questions for More RAM

Sat Dec 17, 2016 7:17 pm

I have read many a technical explanation for the GPU's 1GB Memory limit, how VideoCore V was cancelled, et cetera. I have some questions on possible methods for adding more RAM and want to know why they would/would not work. I don't find the 1GB RAM limit too bothersome, but I find it interesting and want to learn more about the VideoCore IV GPU on this topic.

1. Why did Broadcom choose to dump VideoCore V in the first place?
2. Does the 1GB RAM limit affect every device (besides the Raspberry Pi) that has a VideoCore IV GPU?
3. Why is Broadcom dumping so many products, it seems, these days?
4. Does Broadcom make processors with Mali bolted on, or not?
5. Would it be cost-effective to modify the VideoCore IV to support more than 1GB RAM? Furthermore, is it possible that Broadcom would fund this themselves because it benefits them?
6. Is there a chance Broadcom would pick up VideoCore V in the future again, or have they closed VideoCore development completely?
7. Instead of having the GPU boot the ARM cores and run the basic setup instructions (thus the 1GB limitation), is it possible to make a processor which has the CPU do the startup instructions instead of the GPU? Would this remove the 1GB roof?
8. VideoCore V was incomplete, with only some hardware done. How hard would it be to bolt on the codecs and such from the previous version that were not done yet, to have a VideoCore V/VideoCore IV hybrid chip?
9. How many years out is 28nm at Broadcom?
10. Does Broadcom license out VideoCore IV to other companies, like ARM to Mali? I am curious, because there has been word that Intel would make a limited selection of ARM processors at 14nm. Could VideoCore IV be manufactured at other firms, like Allwinner, MediaTek, Intel, or Qualcomm and get their improved manufacturing processes?
Update: 11. I know Mr. Anholt is writing an OpenGL driver. Does anyone know why the code on GitHub says it has hardly been changed in months?

fruitoftheloom
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Re: GPU Questions for More RAM

Sat Dec 17, 2016 7:31 pm

Broadcom who developed the VideoCore is not the same company as Broadcom today:

https://en.wikipedia.org/wiki/Broadcom
Retired disgracefully.....

jamesh
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Re: GPU Questions for More RAM

Sat Dec 17, 2016 9:59 pm

gtechn wrote:I have read many a technical explanation for the GPU's 1GB Memory limit, how VideoCore V was cancelled, et cetera. I have some questions on possible methods for adding more RAM and want to know why they would/would not work. I don't find the 1GB RAM limit too bothersome, but I find it interesting and want to learn more about the VideoCore IV GPU on this topic.

1. Why did Broadcom choose to dump VideoCore V in the first place?
2. Does the 1GB RAM limit affect every device (besides the Raspberry Pi) that has a VideoCore IV GPU?
3. Why is Broadcom dumping so many products, it seems, these days?
4. Does Broadcom make processors with Mali bolted on, or not?
5. Would it be cost-effective to modify the VideoCore IV to support more than 1GB RAM? Furthermore, is it possible that Broadcom would fund this themselves because it benefits them?
6. Is there a chance Broadcom would pick up VideoCore V in the future again, or have they closed VideoCore development completely?
7. Instead of having the GPU boot the ARM cores and run the basic setup instructions (thus the 1GB limitation), is it possible to make a processor which has the CPU do the startup instructions instead of the GPU? Would this remove the 1GB roof?
8. VideoCore V was incomplete, with only some hardware done. How hard would it be to bolt on the codecs and such from the previous version that were not done yet, to have a VideoCore V/VideoCore IV hybrid chip?
9. How many years out is 28nm at Broadcom?
10. Does Broadcom license out VideoCore IV to other companies, like ARM to Mali? I am curious, because there has been word that Intel would make a limited selection of ARM processors at 14nm. Could VideoCore IV be manufactured at other firms, like Allwinner, MediaTek, Intel, or Qualcomm and get their improved manufacturing processes?
Update: 11. I know Mr. Anholt is writing an OpenGL driver. Does anyone know why the code on GitHub says it has hardly been changed in months?
Answered the parts I am allowed to answer, or I know answers to.

1. They shut down the mobile division, VC development was part of that.
2. I believe so. But remember the VC4 can be used as a co-processor (and was in the Nokia 808), with it's own SDRAM so its not necessarily a limitation in certain circumstance.
4. Don't think so, but haven't worked there since the mobile division was shut down. They may well do now. VC3/4 was better than Mali when it was first released.
5. Cost effective? Who knows, would need some very serious investigation.
9. Who knows, that would be a trade secret. They already have 28nm parts for other parts of the business, but it's a big job moving to another process node.
10. I'm not aware of VC being licensed to other companies, but that is a Broadcom decision, and would be pretty private, so may or may not have happened.
11. Not sure, there is constant development (see the bug reports), maybe the work is done privately, and only pushed to github for major releases.
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fruitoftheloom
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Joined: Tue Mar 25, 2014 12:40 pm
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Re: GPU Questions for More RAM

Sat Dec 17, 2016 10:07 pm

gtechn wrote:11. I know Mr. Anholt is writing an OpenGL driver. Does anyone know why the code on GitHub says it has hardly been changed in months?
http://anholt.livejournal.com
Retired disgracefully.....

6by9
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Re: GPU Questions for More RAM

Sat Dec 17, 2016 10:59 pm

2- Yes and no. There was a chip which had memory controllers for the Arm and vc. The arm could address more memory than vc, so you did have to play a few special games to make sure any shared resources were in the bit vc could see. Memory says one phone did ship with 1.5GB of ram.
7- done in several other chips. It doesn't inherently change memory addressing.
9- it's more a question of converting all the hardware blocks to use 28nm libraries, verifying timing on all of them, and then laying out a chip. Broadcom have produced chips on 28nm, so there's nothing mythical there.
11- check the various branches he has up there. Development is still ongoing. You've already been given a link to his livejournal blog.
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