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rpdom
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Re: Should I wait for the next revision of the pi 4

Fri Jul 05, 2019 8:19 pm

DougieLawson wrote:
Fri Jul 05, 2019 8:16 pm
Who says you couldn't stack the BCM2837 on top of the RAM? Rather than the conventional arrangement on the Mk1 Raspberries.
So all the pins from the SoC would have to be passed through the RAM chip to get to the PCB?

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DougieLawson
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Re: Should I wait for the next revision of the pi 4

Fri Jul 05, 2019 8:20 pm

rpdom wrote:
Fri Jul 05, 2019 8:19 pm
DougieLawson wrote:
Fri Jul 05, 2019 8:16 pm
Who says you couldn't stack the BCM2837 on top of the RAM? Rather than the conventional arrangement on the Mk1 Raspberries.
So all the pins from the SoC would have to be passed through the RAM chip to get to the PCB?
RPi Zero doesn't use all the pins.
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Re: Should I wait for the next revision of the pi 4

Fri Jul 05, 2019 8:24 pm

DougieLawson wrote:
Fri Jul 05, 2019 8:20 pm
rpdom wrote:
Fri Jul 05, 2019 8:19 pm
DougieLawson wrote:
Fri Jul 05, 2019 8:16 pm
Who says you couldn't stack the BCM2837 on top of the RAM? Rather than the conventional arrangement on the Mk1 Raspberries.
So all the pins from the SoC would have to be passed through the RAM chip to get to the PCB?
RPi Zero doesn't use all the pins.
It uses enough. All the first bank of GPIOs, the USB, HDMI and CSI ports, plus power pins. A serious custom PUP (Package Under Package) RAM chip would be needed.

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Re: Should I wait for the next revision of the pi 4

Fri Jul 05, 2019 8:34 pm

DougieLawson wrote:
Fri Jul 05, 2019 8:16 pm
W. H. Heydt wrote:
Fri Jul 05, 2019 8:02 pm

Despite the package size, the BCM2837 (and the, basically discontinued, BCM2836) can't use PoP RAM because the actual chip inside is too big to provide space for the top connections. And PoP RAM is required for the Pi0/Pi0W because there simply isn't space on the board to put a separate RAM package--and you can't put it on the bottom because part of the cost savings in manufacturing is only soldering on one side. So until you can catch an ARMv7 or ARMv8 SoC that includes at least a VC4 AND is small enough to use PoP RAM an upgrade to the Pi0/Pi0W just isn't going to happen.
Who says you couldn't stack the BCM2837 on top of the RAM? Rather than the conventional arrangement on the Mk1 Raspberries.
rpdom and myself. That's two and counting.

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Re: Should I wait for the next revision of the pi 4

Fri Jul 05, 2019 10:40 pm

W.H Heydt, I'm not a computer hardware or software expert, that is not my real job either, based on the situation involving the RPI0/RPI0W, supposedly you can't migrate the RPI2/RPI3 CPU to the RPI0 form factor, because there is not enough room for the ram/GPU, with the RPI3 the ram is located on the underside of the board, you said the cost of production or something is in excess to the actual cost of the computer, well here are 2 pictures comparing RPI computers:

Raspberry Pi 3 - Model B+:
Image

Raspberry Pi Zero:
Image

On the RPI3, the CPU, GPU are visible, the ram is on the other side of the board, the RPI0, you only see the system on a chip, there are no components on the other side, this is the reason why the RPI0 has such a small form factor, all of the computer components are contained with the CPU chip, for the RPI0 lineup to continue being developed, the people at Broadcom or wherever would need to know how to include more ram within the SOC design used on the RPI0 or the RPI A series computer.

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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 12:35 am

Moonmarch wrote:
Fri Jul 05, 2019 10:40 pm
W.H Heydt, I'm not a computer hardware or software expert, that is not my real job either, based on the situation involving the RPI0/RPI0W, supposedly you can't migrate the RPI2/RPI3 CPU to the RPI0 form factor, because there is not enough room for the ram/GPU, with the RPI3 the ram is located on the underside of the board, you said the cost of production or something is in excess to the actual cost of the computer, well here are 2 pictures comparing RPI computers:

...

On the RPI3, the CPU, GPU are visible, the ram is on the other side of the board, the RPI0, you only see the system on a chip, there are no components on the other side, this is the reason why the RPI0 has such a small form factor, all of the computer components are contained with the CPU chip, for the RPI0 lineup to continue being developed, the people at Broadcom or wherever would need to know how to include more ram within the SOC design used on the RPI0 or the RPI A series computer.
It might be possible to cram all, or most of a Pi3B onto a Pi0 form factor, though a better model would be try to figure out how to reduce the size of Pi3A+, since that way you're starting without a lot of the stuff that differentiates the Pi0W. It's going to cost quite a bit more than $5 (or $10 with WiFi) though, and that's the point. The Pi0 is intended to be REALLY, REALLY cheap and making a cut down Pi3A+ isn't going to be cheap.

In your last paragraph you clearly show that you haven't been paying attention to what at least 3 of us have been telling you. Broadcom doesn't put DRAM in the SoC. It's a separate chip in a separate package (and made by other companies, at that). If you look carefully--at a real Pi0 if you can't see it in the picture you posted (I can, but I know where to look)--you can see that there are actually two chip packages there. One on top of the other. The bottom one is the SoC. The top one is the RAM. That's the "package on package" (aka PoP) that we've been talking about. The need to do it that way--because soldering *anything* on the bottom of the board raises manufacturing cost and there simply isn't *room* to put it on the top of the board by itself--is one of the significant constraints to upgrading the Pi0. Unless you want a significantly more expensive board, the SoC *must* support PoP RAM...and the other SoCs (BCM2836, BCM2837) used up through the Pi3+ boards can't do that because the actual silicon chip is TOO BIG to do PoP RAM. With the Pi4 SoC, the BCM2711, you have the issue that it uses a completely different RAM type, LPDDR4 vs. (the older) LPDDR2. But the issue is *still*...gotta be able to use PoP RAM.

And for the history of all, the Model B, B+, Model A, A+, CM...in fact ALL Pis that use(d) the BCM2835 use(d) PoP RAM.

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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 12:36 am

drgeoff wrote:
Fri Jul 05, 2019 8:34 pm
DougieLawson wrote:
Fri Jul 05, 2019 8:16 pm
W. H. Heydt wrote:
Fri Jul 05, 2019 8:02 pm

Despite the package size, the BCM2837 (and the, basically discontinued, BCM2836) can't use PoP RAM because the actual chip inside is too big to provide space for the top connections. And PoP RAM is required for the Pi0/Pi0W because there simply isn't space on the board to put a separate RAM package--and you can't put it on the bottom because part of the cost savings in manufacturing is only soldering on one side. So until you can catch an ARMv7 or ARMv8 SoC that includes at least a VC4 AND is small enough to use PoP RAM an upgrade to the Pi0/Pi0W just isn't going to happen.
Who says you couldn't stack the BCM2837 on top of the RAM? Rather than the conventional arrangement on the Mk1 Raspberries.
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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 1:09 am

If the next RPI0 is not possible that is only, because the current components available for RPI computers are not compatible with the SOC design that is all that you are telling everyone, perhaps the RPI0 will be redesigned from scratch instead of using the original design who knows, I didn't say there is a RPI0 being developed I was only talking about different RPI computer models, I didn't say save up your money for the next RPI release, no my original post in this topic was I said a new RPI computer model is released every year on average, people decide when to purchase a RPI computer for their own reasons, this conversation is completely not necessary at all, talking about all of these various tech specs most people would not understand.

I didn't notice until now you will see the Elpida logo on the RPI0 CPU chip, not Broadcom, searching Google, Elpida Memory Inc. is a memory company that sells DRAM, and was bought out by Micron Technology in 2013.

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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 1:36 am

The Elpida logo isn't on the CPU (actually an SOC), it's on the RAM chip, which is mounted on top of the SOC.

The earlier post about the Pi3 CPU and GPU being visible, one of those is an SOC which has both CPU and GPU in it. The other big black chip near the USB is not a GPU, but a USB/ethernet hub chip.

I don't doubt somebody could make a better Pi0, after all there are full x86 computers the size of a full size SD card.
The issue however, would be producing it and selling for a profit at the current price.
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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 2:51 am

Imperf3kt wrote:
Sat Jul 06, 2019 1:36 am
The issue however, would be producing it and selling for a profit at the current price.
Yup, that's really what it all comes down to. The Pi Zero is the $5 Raspberry Pi (the only computer given away on magazine covers).

No way you're gonna hit that price point with the Pi3 SoC, even if you could squeeze it into the same form-factor (highly doubtful). So what you'd end up with is a larger and more expensive board. Hmm... what should we call it... perhaps the Pi 3A+ :?: How does that sound?

And what does any of this have to do with the topic question, Should I wait for the next revision of the pi 4 ? :?
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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 3:31 am

I don't doubt somebody could make a better Pi0, after all there are full x86 computers the size of a full size SD card.
The issue however, would be producing it and selling for a profit at the current price.
Well the BCM2708 is made in 40nm, eventually the fab will stop making them?
A dual core A32 or A35 in 28nm or 16nm would have smaller dies sizes so should be cheaper.
But the VC4 is a big part of the silicon, who would want to make a spin of that and hope it scales?

However we now have a VC6 in 28nm that works in the BCM2711 on the Pi4.
Zero+ with dual core A3x and VC6, same footprint just USB-C and dual micro HDMI?
Could it be made for the same price? $5 Desktop replacement :o 8-) :lol:
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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 7:26 am

Gavinmc42 wrote:
Sat Jul 06, 2019 3:31 am
Well the BCM2708 is made in 40nm, eventually the fab will stop making them?
A dual core A32 or A35 in 28nm or 16nm would have smaller dies sizes so should be cheaper.
But the VC4 is a big part of the silicon, who would want to make a spin of that and hope it scales?
Fabs are still making 65, 90, and 180nm silicon as it is very reliable as a process, and has some benefits with reliability and ESD resilience.
You're still limited on the ball out of the package - you can fit more gates in, but struggle on adding additional external functionality.
And the ARM cores are becoming bigger than Videcore these days.
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Re: Should I wait for the next revision of the pi 4

Sat Jul 06, 2019 9:02 am

And the ARM cores are becoming bigger than Videcore these days.
So next shrink to 16nm and we get two VC6s?
In 28nm the VC6 is smaller than the VC4 = faster?

How big is the L2 cache?
Is it the biggest part of the die?

To make the 100Millions of BCM2711 to fill sales need lots of dies per wafer, not going to use large transistors for that.
What is the wafer size and how big is the BCM2811 die?
Nerds like me who used to be in the semi business like to know that stuff.
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Re: Should I wait for the next revision of the pi 4

Sun Jul 07, 2019 5:13 am

Well I would not be surprised if they separated CC1 and CC2 and added another 5k pulldown resistor.
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Re: Should I wait for the next revision of the pi 4

Sun Jul 07, 2019 5:22 am

Gavinmc42 wrote:
Sat Jul 06, 2019 9:02 am
And the ARM cores are becoming bigger than Videcore these days.
So next shrink to 16nm and we get two VC6s?
In 28nm the VC6 is smaller than the VC4 = faster?

How big is the L2 cache?
Is it the biggest part of the die?

To make the 100Millions of BCM2711 to fill sales need lots of dies per wafer, not going to use large transistors for that.
What is the wafer size and how big is the BCM2811 die?
Nerds like me who used to be in the semi business like to know that stuff.
Last I heard, the standard wafer size was 300mm, but that was a while ago. I'm not sure if the economies scale to larger wafers.

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Re: Should I wait for the next revision of the pi 4

Sun Jul 07, 2019 8:56 am

I saw those xrays pics but silicon seemed transparent, hard to detect the die sizes.
Going form 28nm to 16nm will triple the number of die on a 300mm wafer.
If the Pi4 is so successful that more chips are needed we may get a revision.

I have no idea of the capacity of a modern 300mm 28nm FAB.
But 28nm is not really "modern" compared to what the big guys use.
Anyway I was just wondering if the caches were big enough to fit a microkernel.
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