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rpdom
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Re: extra RAM

Mon Sep 03, 2012 7:00 am

mikerr wrote:Model A is a different pcb with all the extra manufacturing / testing time that that requires.
As I understand it, the model A uses exactly the same board as the B, just with a few less components and a couple of links to take the single USB direct from the SoC to the USB socket, rather than the LAN/USB chip which isn't present on the A.

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Re: extra RAM

Mon Sep 03, 2012 7:09 am

Jim JKla wrote:It felt odd to me that the difference between the "A"&"B" included lower memory as well as dropping the Ethernet and twin USB we may even get the "C" or is it the "B+" or the "B512" before the "A" ;)

I would probably get one of the memory expanded ones but like the "A" I can see it being a wait. :)
Model A is meant to have the same amount of RAM as stated when the model B first came on sale back in March. Model A has 256mb RAM.

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Re: extra RAM

Mon Sep 03, 2012 7:18 am

Look here under General

http://www.raspberrypi.org/faqs

I had not seen any anouncement of the change from 128Mb to 256Mb for the "A" and it was searching for this information that I found the strikethtough 128Mb.

This is a remark on my observation skills rater than any omision of an anouncement. ;)

I obviously stand corrected. ;)
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Re: extra RAM

Mon Sep 03, 2012 7:26 am

The A Model is the same PCB (board) as the B Model, but does not have the LAN9512 chip installed. They jumper through the area of the LAN9512 to a single USB connector. There is no Ethernet connector. SoC and Memory are the same. It could also be made with the 512MB DDR400 memory package.

Parts changed on A model:
LAN9512 "chip", gone
Ethernet connector, gone
Single 140ma polyfuse (now single 0ohm resistor).
Single USB connector in place of double USB connector.

Everything else should be the same. ;)
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Re: extra RAM

Mon Sep 03, 2012 7:29 am

So theoretically the "A" could go 512Mb at the same time as a remodeled "B" Y/N?
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Re: extra RAM

Mon Sep 03, 2012 7:38 am

Jim JKla wrote:So theoretically the "A" could go 512Mb at the same time as a remodeled "B" Y/N?
Yes: It uses exactly the same parts as the Raspberry Pi B Model, just a few less parts. Memory is just sourcing a different component and putting it into the manufacturing line. there will be no difference in the Operating Systems. Settings in the OS may differ.

The only real changes I see would be that some different Start.elf files would be needed.
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Re: extra RAM

Mon Sep 03, 2012 8:01 am

Lob0426 wrote:480/32 (would not even bother with this one)
I'd consider leaving this in for completeness and future proofing there's no telling what will pop up.

To be fair I think you have covered the bases. ;)
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Re: extra RAM

Mon Sep 03, 2012 8:02 am

Lob0426 wrote:The A Model is the same PCB (board) as the B Model, but does not have the LAN9512 chip installed. They jumper through the area of the LAN9512 to a single USB connector.
Hmm, how hard would it be to hack an existing model B into an A ?
The LAN9512 is quite power hungry (relatively) - I know you can power it down in software,
but has anyone done that and then wired out the single Broadcom USB ?
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Re: extra RAM

Mon Sep 03, 2012 8:03 am

Lob0426 wrote:480/32 (would not even bother with this one)
I'd consider leaving this in for completeness and future proofing there's no telling what will pop up.

To be fair I think you have covered the bases. ;)
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Re: extra RAM

Mon Sep 03, 2012 9:24 am

mikerr wrote:
Lob0426 wrote:The A Model is the same PCB (board) as the B Model, but does not have the LAN9512 chip installed. They jumper through the area of the LAN9512 to a single USB connector.
Hmm, how hard would it be to hack an existing model B into an A ?
The LAN9512 is quite power hungry (relatively) - I know you can power it down in software,
but has anyone done that and then wired out the single Broadcom USB ?
There have been one or two posts indicating that some people have doone this.

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Re: extra RAM

Mon Sep 03, 2012 9:39 am

Why does this feel like someone hacking of their own limbs to take part in the paralympics.

It does rather look like a lack of patience.

I would dearly love to have a model "A" to work with but I don't feel the need to sacrifice a working model "B" to do it, that is along the lines of jumping out of a servicable aircraft to test a parachute (someting else I will not be doing). ;)
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Re: extra RAM

Mon Sep 03, 2012 9:58 am

Dig dig dig...

Ah yes, a few have done it already:

http://www.raspberrypi.org/phpBB3/viewt ... 2&p=131332

http://www.raspberrypi.org/phpBB3/viewt ... 36#p118042
(remove LAN9512 and solder usb to R36 and R37)

I can see doing it for power saving purposes as well as the voltage regulator replacement (together they probably save 40%).
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Re: extra RAM

Mon Sep 03, 2012 10:03 am

How much time they have saved rather depends on how long it takes for us to get production model "A's"
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Re: extra RAM

Mon Sep 03, 2012 1:34 pm

I've deleted a couple of posts of speculation here which were sparked off by a comment from one of our suppliers in order that we do not end up Osbourne Computer Companying ourselves - we are NOT releasing a $50 512MB model. I've just to shout down a phone about it; that supplier has read that it's a frequently requested thing, and had put a placeholder on their site in case because they wanted to talk to us about whether we wanted to do it.

We don't, and you will notice that there is no longer a placeholder on their site!

We do encourage speculation and discussion of what future Pis might be like - but we will ANNOUNCE them when they happen. Promise.
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Re: extra RAM

Mon Sep 03, 2012 1:48 pm

I am still trying to get one without an Ethernet connection and what appears to have been an error on my part less RAM :D

The prommise of an "A" could be stopping buying another "B" if it wasn not for the fact I'd have to scrape the barrel to get the "A" in the first place.

I wonder how much I could get for my Osbourne? :)
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Re: extra RAM

Mon Sep 03, 2012 5:14 pm

Don't worry - the A's are still on the way, certainly by end of year, and hopefully much sooner than that.
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Re: extra RAM

Mon Sep 03, 2012 8:31 pm

liz wrote:I've deleted a couple of posts of speculation here which were sparked off by a comment from one of our suppliers in order that we do not end up Osbourne Computer Companying ourselves - we are NOT releasing a $50 512MB model. I've just to shout down a phone about it; that supplier has read that it's a frequently requested thing, and had put a placeholder on their site in case because they wanted to talk to us about whether we wanted to do it.

We don't, and you will notice that there is no longer a placeholder on their site!

We do encourage speculation and discussion of what future Pis might be like - but we will ANNOUNCE them when they happen. Promise.
I will admit that I was a trifle startled to see the listing this soon (in another year, there would be no surprise at all), and the listed price was interesting, to say the least. Especially in light of posts that alluded to much higher part prices for the larger RAM module were claimed to be.

However, I also noted that there was no indication of just *when* such an upgraded version would be available. Given the problems both major suppliers are having getting enough Pis to get rid of order backlogs, much as a 512MB model (even at $50) is interesting, it is rather too soon.

On the other hand, it does show that what several of us have speculated about--512MB RAM units coming far enough down in price to make a 512MB Pi feasible in the near future (just not *this* near)--is not nearly as far fetched as some would have it.

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Re: extra RAM

Mon Sep 03, 2012 9:43 pm

The real problem is that there is still a backlog of B Models. Allowing a 512MB B Model to hit the market right now could cause problems. Many people would sit and wait for the 512MB. The real goal of the Foundation has been the A Model, the $25 Linux Box! They are not going to want anything coming out that might delay it getting to market. Oh, and that new backlog is cleared up. As with the B Model, you can expect the A Model to be very popular.

The Foundation really stuck to the 128MB until it was a matter of the cost being well within the $25 price range with the 256MB. The Foundation believed the 128MB met their goals, as well as the single USB and no Ethernet.

So basically I am waiting for the A Model to get out. Then I think we may just see 512MB models of both A & B. Next spring maybe! I think we will see a PCB revision about then also, that incorporates some changes. Like eliminating the USB polyfuses, disconnecting the 1v8 rail and now the removal of C14(HDMI?). Some of these things will reduce the component cost, but more importantly increase stability and overall flexibility.

Edit: not C14. It's D14!

I think my biggest question right now is;
Will the A Model require a new emissions certification?
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Re: extra RAM

Tue Sep 04, 2012 3:07 am

Lob0426 wrote:Then I think we may just see 512MB models of both A & B. Next spring maybe! I think we will see a PCB revision about then also, that incorporates some changes. Like eliminating the USB polyfuses, disconnecting the 1v8 rail and now the removal of C14(HDMI?). Some of these things will reduce the component cost, but more importantly increase stability and overall flexibility.

Edit: not C14. It's D14!

I think my biggest question right now is;
Will the A Model require a new emissions certification?
Liz has already mentioned the intention to bridge the F1 and F2 polyfuses (the 0 ohm resistors being an interim step) and people are already seeing boards without D14.

*IF* there is an actual board revision in your time frame, it would probably be to fix the fight between the voltage regulator on the board and the one in the USB/Ethernet chip--isolating those two from each other.

As for when we'll see 512MB Pis....I would guess *at* *least* six months and probably more. If the distributors get a go ahead to make more expensive unit, we'll see them sooner. If the Foundaion insists on "no special versions, and all versions must adhere the specified price point"...then I'd guess more like a year. Could be longer, could be shorter. It all depends on what the price of RAM PoPs does.

I say "at least six months" because I don't expect the A+B backlog to away any faster than that. The only things that would cause me to revise that would be either a truly drastic reduction in memory (if the 512MB gets cheaper than the 256MB is now, there would be no point in waiting). I mean a reduction like the one when IBM in one step dropped the price of mainframe memory from $75,000 per megabyte to $15,000 per megabyte (yeah...it was a while ago). Or a massive increase in production capability...going from the current 4K per day to something like 10K to 20K per day.

In the mean time, Liz is probably leaning back in her chair and laughing at me...

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Re: extra RAM

Tue Sep 04, 2012 6:43 am

Liz doesn't laugh - she cackles and Bwwahahahahaha's

You all just have to wait! As with anything Raspi related! Small team + much work = longish timescales.
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Re: extra RAM

Thu Sep 06, 2012 7:59 pm

I'm in the "keep the resource reasonable and code efficient" camp. i.e. no 512MB model yet. I'm sure the foundation will resist it as long as possible, but it will come.
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Re: extra RAM

Thu Sep 06, 2012 9:12 pm

arm2 wrote:I'm in the "keep the resource reasonable and code efficient" camp. i.e. no 512MB model yet. I'm sure the foundation will resist it as long as possible, but it will come.
The first machine code I wrote was a View Printer Driver for the BBC B I had a whole 128 bytes to play with! I was very proud with what I achieved.
Well... The IBM 1401 (released in 1959, first really widespread business computer that IBM made) had a minimum memory config of 1.4K characters. The IBM 1620 (released in 1957, a "scientic and engineering" machine) was considered pretty good sized at 20K *digits* for the base system and expandable to 100K digits. The System/360 family had a theoretical max memory of 16MB (what you could install varied by model...the Model 30, for instance was limited to 64K bytes).

I think it just goes to show that what is "small" or "large" amounts of memory depends on where and when you sit.

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Re: extra RAM

Thu Sep 06, 2012 11:30 pm

Where extra RAM would help is in the projects. Probably not needed for education. I saw one member who is portingg EMC2, a controller program for CNC milling and machining. He really could use the extra RAM. Another is trying to set up a RasPI based MMO. I would guess he could use it also. The people that are running RasPii as media center will use it too. They can give the GPU 128Mb and still have 384MB for the processor. More RAM left than is in the current model. I am sure there will be other uses such as Servers where it will mean less or no reliance on swap (virtual memory). You will be able to run your server and that motion control program plus the home automation on one little RasPi Server.

If you do not think that you can code ineffiently in 256MB then you need to think again. There will always be that temptation to just push a little in to a swap file. Or save data on an 8GB stick because you don't want to optimize the code or settings. Efficiency is taught or learned, not constrained!
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Re: extra RAM

Fri Sep 07, 2012 2:21 am

Lob0426 wrote:Efficiency is taught or learned, not constrained!
As I learned when an Engineering student many years ago...

"Efficiency" depends on what you are trying to effic.

As for programming... In most programming, optimiztion is left up to the compiler because when done by hand, it usually results in code that no one--not even the original author--can enhance or fix. Sometimes, when code is too clever by half (read up on the original troff), when you *do* have to change it, the original author is *dead* and no one living can figure out how it works in less time than it takes to write a new version from scratch (read up on ditroff).

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Re: extra RAM

Fri Sep 07, 2012 6:55 am

Surely W.H.Heydt the troff ditroff story is as much a fable in support of adequate support documentation than over efficient code.

There will be students who produce elegant tight code to run in and within the restraints of the RPi but it is unlikely that student code produced on the RPi will enter the main stream as is, but lessons in optimisation at the expense of adequate documentation will be lessons learned well in the RPi environment.

There were screams of derision at the spaghetticode produced in Basic on BBC and Spectrum but this spaghetticode was just as good at teaching the student the basic structures of loops etc. well documented or not these structures were later lessons incorporated into a relatively more structured environment like Pascal C++.

If there is any lesson that will come from a memory constrained RPi be that 256 or 512 it will be that bloat is not the answer.

However constrained it will never be as constrained as a 16k Spectrum. I remember being forced by necessity to upgrade my 16k to 48k by inserting ram as dip chips terrified I was going to blow away my first and only computer at the time.

There will always be a section of the community that will desire a faster bigger model the only way to achieve this in those heady days of my youth was to change programming language to relatively obscure subsets of the genre like Forth and the mind numbing vagaries of reverse polish notation. (It was mind numbing at the time) the ultimate step for me being pure Assembler.

Lessons that sat in the back of my mind all those years ago did become useful when in later years when I ran headlong into assembler for a second time studying computing for industry as a mature student at university.

It would have been better if the course had used z80 assembler but I was confronted by a package that used the 68000 series chip. You can't have everything. ;)
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