styrmand
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Re: Amount of RAM

Sun Mar 11, 2012 11:15 am

I am sure the amount of RAM on RPI has been discussed before (if it is to much or to small), so that's not the issue, with this question.

Instead i am wondering in more general terms, why there very often seems to small amounts of ram on different devices -what is determining the size of the RAM.

As an other example i have been using a Synology 107 NAS server for several years. It has only 64MB of ram. It has the potential to be used as a small web-server, but the smalla amount og RAM, seems to limit this.

The RPI has 256 MB, but why not 1 GB?

As i see it there can be several causes, but i can't figure out which are most important.

1) RAM cost money. The price of RAM is very low, so it could probably make a difference in a few dollars 5-10$ or so.

2) More RAM more power needed?

3) More RAM a much more expensive product. That is the reason for many proprietary solutions, but absolutely not an argument for RPI.

4) Other technical hurdles? Is it the CPU, that cant address big amount of RAM quickly enough or…?

Does anyone have an idea about why RAM always seems to be dimensioned as "just  enough", instead of "just plenty"?

What has been the criterias from RPI designers perspective?

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scep
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Re: Amount of RAM

Sun Mar 11, 2012 11:20 am

In the Pi's case – cost.

Even a few dollars is a big percentage rise at this price point. And the selling price was a critical factor for the Foundation.

styrmand
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Re: Amount of RAM

Sun Mar 11, 2012 11:23 am

So if it was not for the money, it wouldn’t create new problems making RPIs with 1GB or 8GB?

jamesh
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Re: Amount of RAM

Sun Mar 11, 2012 11:24 am

From the Raspi perspective, the jump from 256 to 512 was too great, making a BIG difference  to the price. 512 PoP ram is very expensive. As to other mem size, they are no not made in the larger sizes in the right PoP format. The CPU can address 1GB I think, maybe more.

In other products, it's also about cost. Why put more <whatever> you need in a device? It make the product cost more for no added benefit. You example, the product works fine on 64MB. Why put more in? Just makes the end user price more expensive, or makes your profit margin lower.
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Gert van Loo
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Re: Amount of RAM

Sun Mar 11, 2012 11:29 am

Well.. not only money.

The ram interface is a based on the JDEC PoP 168 LPDDR2 standard. That limits you to certain types of memory: 32 bits wide 1 or 2 chip selects and max ?? address lines (Sorry can't remember the exact number) . That particular part of the standard goes up to max 2Gbyte. Also the Raspberry Pi SDRAM interface has only one Chip-Select, thus we can use only half of that: 1Gbyte. Next you have to find a manufacturer who has a single 1Gbyte (8Gbit) LPDDR2 die in that specific package. Which at the moment is none.

So no 1Gbyte for the Pi for a while. As the LPDDR2 standard is getting older there is less chance that memory vendors will come up with a new bigger product for it.

richard77
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Re: Amount of RAM

Sun Mar 11, 2012 11:31 am

The ram used is PoP type (i.e. the chip soldered on the board and the ram is soldered on the chip)

This special type or RAM package is available only on 128 and 256 MB (at least for reasonable price).

styrmand
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Re: Amount of RAM

Sun Mar 11, 2012 11:48 am

From my perspective - I know very little about electronics - i just see the prices of RAM drop down to almost nothing. But now I understand about the more special PoP-RAM.

The reason I ask about this RAM issue, is because I have a plan of using (at least trying to use) my RPI as a development LAMP server. 256  MB is absolutely okay. On the other hand a server can use all the RAM it can get - but it is just visions in my head for now.

I am really looking forward to experiment with the unit, when I get my hands on one (Still waiting to hear more from the shop - and just as exited as everybody else. )

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Gert van Loo
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Re: Amount of RAM

Sun Mar 11, 2012 11:58 am

There is a 512Mbyte PoP available which is compatible with the Raspberry-Pi. It is rather new so I expect the price to be high for a while.

Then there is the time and effort required to bring out derivatives of a product**. As that is now done by Farnell & RS I expect that to be a much lesser issue then if the Foundation had to do it. Another advantage for outsourcing!

** For a derivative product there is a lot more work beyond 'just' swapping of memories on a feeder tray of a pick-and-place machine.

Beta-guy
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Re: Amount of RAM

Sun Mar 11, 2012 12:15 pm

is it possible to make a Raspberry pi without ram, just a ram slot for a DDR/DDR2/DDR3 SODIMM module?

drgeoff
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Re: Amount of RAM

Sun Mar 11, 2012 12:25 pm

Anything is "possible" but don't hold your breath waiting.  Just the board space for all the tracks and the socket will increase the price.  Sockets are not cheap either.

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Gert van Loo
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Re: Amount of RAM

Sun Mar 11, 2012 2:17 pm

Beta-guy said:


is it possible to make a Raspberry pi without ram, just a ram slot for a DDR/DDR2/DDR3 SODIMM module?



Impossible! You need LPDDR2 not DDR2 or DDR3. There are no modules for that. Also it is PoP Package-On-Package. This means there are BGA landing pads at the top of the BMC2835. BGA means you have to solder a chip on there. There is no way to connect modules to it or make anything pluggable.

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Re: Amount of RAM

Sun Mar 11, 2012 2:58 pm

I have in my mind's eye a typical desktop PC running Windows 7 - and my claim that it is a souped up Raspberry Pi.  I just replaced the ARM chip in the Pi with whatever the latest from Intel is.  I replaced the memory with standard DDR3 memory (and bumped it up to 8G).  I added a screen.  I replaced the power supply.  I replaced the motherboard...

etc, etc.  Now I've got the kind of Pi that the OP wants.  And I'll sell it to him cheap.  Not as cheap as the Foundation sells Pis for, but you know, mine is so much better.  A steal at 20 times the cost of the original Pi.  So much betterer.  So much more to his liking.  It even has VGA native output.
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axiomprime
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Re: Amount of RAM

Sun Mar 11, 2012 3:18 pm

Theres a beagle board for about double the price thats got more muscle and RAM.

axiomprime
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Re: Amount of RAM

Sun Mar 11, 2012 3:24 pm

Actually, the one I was on about is more like four times the price. I got a dual core 1.6ghz atom mini atx board with 2gb RAM, 120gb hard drive and DVD rewriter for a tenner more than that.

slacer
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Re: Amount of RAM

Sun Mar 11, 2012 5:06 pm

axiomprime said:


Theres a beagle board for about double the price thats got more muscle and RAM.



Sorry, but I cannot find a beagle board for that price.

summers
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Re: Amount of RAM

Wed Mar 14, 2012 10:53 am

Probably thinking of the beaglebone e.g. here:

http://uk.mouser.com/ProductDe.....A%252bMEAl

Phil Spiegel
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Re: Amount of RAM

Wed Mar 14, 2012 11:25 am

Perhaps the next, more advanced Pi should have less RAM - for advanced programmers who recall efficient programming, in pre-bloatware days, or how long it took to key in a boostrap program on a PDP8.

Was it Acorn or Micro User which had the monthly competition for a program in a single line of code?

How much code can a pupil write in 1 lesson, or even a term-long project?

Does anyone here remember the balsa-wood and bits home-made computer in Meccano Magazine?

Encouraging the economical use of resources !

jamesh
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Re: Amount of RAM

Wed Mar 14, 2012 11:55 am

summers said:


Probably thinking of the beaglebone e.g. here:

http://uk.mouser.com/ProductDe.....A%252bMEAl


Just read the lead time on the beaglebone from mouser. 24 weeks. Ouch. Makers our delays look, well, a bit trifling. (touch wood)
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Kernel
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Re: Amount of RAM

Wed Mar 14, 2012 1:46 pm

Phil Spiegel said:


Perhaps the next, more advanced Pi should have less RAM - for advanced programmers who recall efficient programming, in pre-bloatware days, or how long it took to key in a boostrap program on a PDP8.

Was it Acorn or Micro User which had the monthly competition for a program in a single line of code?

How much code can a pupil write in 1 lesson, or even a term-long project?

Does anyone here remember the balsa-wood and bits home-made computer in Meccano Magazine?

Encouraging the economical use of resources !



You could artificially limit the amount of ram available to the OS I guess

summers
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Re: Amount of RAM

Wed Mar 14, 2012 2:11 pm

JamesH said:


summers said:


Probably thinking of the beaglebone e.g. here:

http://uk.mouser.com/ProductDe.....A%252bMEAl


Just read the lead time on the beaglebone from mouser. 24 weeks. Ouch. Makers our delays look, well, a bit trifling. (touch wood)



Well yes, but they do have 461 in stock that they can dispatch now.

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Jongoleur
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Re: Amount of RAM

Wed Mar 14, 2012 2:14 pm

Phil Spiegel said:

Does anyone here remember the balsa-wood and bits home-made computer in Meccano Magazine?


No, but I DO know that Cambridge University Mathematics Lab had a computer made out of meccano in the late 1930s. http://en.wikipedia.org/wiki/D.....l_analyser

And that some clever-clogs has made a Babbage Difference Engine from meccano too.

http://www.meccano.us/differen.....nes/rde_1/



(there's at least one made from lego too...)



The Raspberry Pi seems quite sensible.......
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rmm200
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Re: Amount of RAM

Wed Mar 14, 2012 7:06 pm

Remember too you don't really get 256MB. The greedy GPU will take 1/4 to 3/4 of that,depending on how it is configured. So be thinking about 128MB.

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mahjongg
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Re: Amount of RAM

Wed Mar 14, 2012 11:58 pm

Actually its 1/8th to 1/2 of the available RAM!

The minimum of RAM allocated to video is just 32MB, (leaving 224MB for the CPU) and that is enough for a 1080p framebuffer for Linux.

The default allocation is 64MB, (192MB for the CPU) and that  It should be sufficent for standalone 1080p video decoding, or simple 3D (but probably not both together at the same time).

Dedicating half the RAM (128MB) for video is only needed for heavy 3D, possibly also with video decoding (e.g. XBMC) That is the reason that XMBC and such special applications run on a special "Light linux distro" such as OpenELEC.

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