Hello, a late in the day design query or two here....!
I wondered why an sd card slot was provided on the pi at all, since thumb drives cost peanuts these days and can be booted from. Wouldn't it make more sense and save costs for both manufacturer and consumer to have usb only? If sd card were really needed then an sdcard-to-usb adapter could be made use of.
As a secondarym related question: would it have been technically possible to have designed it so that the usb could be booted if no sd card was present. It seems a little cumbersome to be forced to make use of an sdcard, (particularly when there is no clear benefit of having one at all).
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Re: Naive question: Why have an sd card slot at all?
Because the Raspberry Pi can only boot from an SD-card. You can run one from a USB memory stick, but you still need an SD-card to kick things off.
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Re: Naive question: Why have an sd card slot at all?
The PI cannot boot from USB because there isn't any code in the boot process to utilise the USB ports only code for loading from an SD Card slot. - https://github.com/dwelch67/raspberrypi
Richard S.
Richard S.
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Re: Naive question: Why have an sd card slot at all?
Why from a design point of view? 'There isn't any code'... or 'just because' doesnt address the question.
Why design it that way?
Why design it that way?
Re: Naive question: Why have an sd card slot at all?
The System on a Chip (SoC) that powers the Raspberry Pi is, to my understanding, designed for mobile phones and the like. Therefore it's probably only been designed at the hardware level to boot from an SD card and nothing else.fundamental wrote:Why from a design point of view? 'There isn't any code'... or 'just because' doesnt address the question.
Why design it that way?
Re: Naive question: Why have an sd card slot at all?
This is a purely speculative guess but I would image the code required to support SD card booting was a lot simpler than the code for supporting USB flash drive bootable media.
Why it's that way?? I don't know maybe too hard or not enough memory space for code to exist inside the PI.
Richard S.
Why it's that way?? I don't know maybe too hard or not enough memory space for code to exist inside the PI.
Richard S.
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Re: Naive question: Why have an sd card slot at all?
Could have made it a micro SD though - wouldnt stick out so much.
Looks like the board is blowing a raspberry - at all of us.
Looks like the board is blowing a raspberry - at all of us.
Re: Naive question: Why have an sd card slot at all?
Cost. Fully sized SDcards are cheap all over.pygmy_giant wrote:Could have made it a micro SD though - wouldnt stick out so much.
Looks like the board is blowing a raspberry - at all of us.
Availability. Same with Full Sized SDcards... Easy to obtain just about anywhere.
Size. Imagine in a school environment. Very small easy to lose.
You could use a SDCard adapter (a short one at that) and use a MicroSDHC card (I do), but I would imagine in a class type environment it might be a real problem.
Dweeber A.K.A. Kevin...
My RPI Info Pages including Current Setup - http://rpi.tnet.com
My RPI Info Pages including Current Setup - http://rpi.tnet.com
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Re: Naive question: Why have an sd card slot at all?
Not convinced.
1) In a class environment I would want the SD card locked away inside the case where naughty kids cant tamper with it or accidentally wrench it.
2) Micro SD's are no longer more expensive than chunky ones.
so those are actually 2 reasons for micro SD
1) In a class environment I would want the SD card locked away inside the case where naughty kids cant tamper with it or accidentally wrench it.
2) Micro SD's are no longer more expensive than chunky ones.
so those are actually 2 reasons for micro SD
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Re: Naive question: Why have an sd card slot at all?
Actually, In a class environment, i would want an SD card. That way each student could have their own card with their projects saved on it, saving writes to the SD card which has a limited number of writes, having many students using the same card could cause you to go through more cards than it is worth. They can then plug the card into any PI and use their own computer essentially making the larger harder to lose SD card superior.
Pi with ArchLinux running a minidlna/samba home server
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Re: Naive question: Why have an sd card slot at all?
Dont think the sd card sockets would last long with that sort of punishment.
Better off giving the students flash drives to plug in a hub.
Better off giving the students flash drives to plug in a hub.
Re: Naive question: Why have an sd card slot at all?
If you doubt SD socket can take it then why are you advocating micro SD?
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Re: Naive question: Why have an sd card slot at all?
Because it can be bolted shut inside the case so that nobody can remove it.
Re: Naive question: Why have an sd card slot at all?
I wouldn't mind soldering a Micro-SD holder instead of the SD card holder but I can't find any sold via eBay.
Could anyone recommend a site that sells them (preferably the spring loaded type)??
Richard S.
Could anyone recommend a site that sells them (preferably the spring loaded type)??
Richard S.
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Re: Naive question: Why have an sd card slot at all?
Found some:
http://www.ebay.co.uk/itm/10-PCS-TransF ... 3a7a79acde
you might also need one of these:

http://www.ebay.co.uk/itm/10-PCS-TransF ... 3a7a79acde
you might also need one of these:
Re: Naive question: Why have an sd card slot at all?
adafruit has an awesome "short" adapter so the card doesn't stick out. Their idea is super simple and works great.redhawk wrote:I wouldn't mind soldering a Micro-SD holder instead of the SD card holder but I can't find any sold via eBay.
Could anyone recommend a site that sells them (preferably the spring loaded type)??
Richard S.
https://www.adafruit.com/products/966
Re: Naive question: Why have an sd card slot at all?
ModMyPi also do one which I use and I am buying more for all my pis:cnt wrote:adafruit has an awesome "short" adapter so the card doesn't stick out. Their idea is super simple and works great.redhawk wrote:I wouldn't mind soldering a Micro-SD holder instead of the SD card holder but I can't find any sold via eBay.
Could anyone recommend a site that sells them (preferably the spring loaded type)??
Richard S.
https://www.adafruit.com/products/966
https://www.modmypi.com/shop/sd-cards-a ... rd-adaptor
- tedhale
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Re: Naive question: Why have an sd card slot at all?
I got one to try out, since it seemed like a good idea. The uSD adapter is soldered on top of an SD card connector (as apposed to being built inside of it.)cnt wrote:adafruit has an awesome "short" adapter so the card doesn't stick out. Their idea is super simple and works great.redhawk wrote:I wouldn't mind soldering a Micro-SD holder instead of the SD card holder but I can't find any sold via eBay.
Could anyone recommend a site that sells them (preferably the spring loaded type)??
Richard S.
https://www.adafruit.com/products/966
This makes the adapter too fat to fit in any of my cases. The slot is only big enough for a normal SD card to fit through.
Just a warning, since it didn't "work great" for me. This also won't work for a lot of other people.
- Ted B. Hale
http://raspberrypihobbyist.blogspot.com
http://raspberrypihobbyist.blogspot.com
Re: Naive question: Why have an sd card slot at all?
The SoC requires an SD card to boot from.
uSD sockets are much more fragile that normal SD sockets, the cards are smaller and easier to use, and at the time of design, were relatively uncommon. Also you can get adapters to SD from uSD, but not the other way round, for obvious reasons! My personal preference is for SD, I find the uSD's just too easy to drop and lose.
uSD sockets are much more fragile that normal SD sockets, the cards are smaller and easier to use, and at the time of design, were relatively uncommon. Also you can get adapters to SD from uSD, but not the other way round, for obvious reasons! My personal preference is for SD, I find the uSD's just too easy to drop and lose.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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Contrary to popular belief, humorous signatures are allowed.
I've been saying "Mucho" to my Spanish friend a lot more lately. It means a lot to him.
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Re: Naive question: Why have an sd card slot at all?
I agree, but I worry about these easy to remove cards in a classroom setting. Any teacher would need to have a strong discipline regime in place to make sure that they didn't end up in little johnny's MP3 player or swiped out of the Pi being used by the freckly girl with braces who everyone picks on as a joke.
I think the ability to tuck the card inside a case out of temptation's way could reduce distraction in lessons and teacher's stress levels, which could make the Pi more appealing to the educational market.
Perhaps that is more an argument for an educational case/adapter combo than changing the board.
I think the ability to tuck the card inside a case out of temptation's way could reduce distraction in lessons and teacher's stress levels, which could make the Pi more appealing to the educational market.
Perhaps that is more an argument for an educational case/adapter combo than changing the board.
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Re: Naive question: Why have an sd card slot at all?
Somebody told me micro SD cards are not allowed in schools or need special precautions because of their size.
Probably because they fall in the category of 'everything small enough that it can be swallowed and obstruct the airway'.
By the way: The BCM2835 CAN boot from USB but NOT trough the LAN chip. Only from a USB directly connected (e.g. model A).
The chips on the Raspberry-Pi are just not programmed to do that.
Probably because they fall in the category of 'everything small enough that it can be swallowed and obstruct the airway'.
By the way: The BCM2835 CAN boot from USB but NOT trough the LAN chip. Only from a USB directly connected (e.g. model A).
The chips on the Raspberry-Pi are just not programmed to do that.
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Re: Naive question: Why have an sd card slot at all?
That's very interesting. You are saying that the Model A could boot from USB - but only if the USB drive is directly connected to the (one and only) USB port on the board.Gert van Loo wrote:By the way: The BCM2835 CAN boot from USB but NOT trough the LAN chip. Only from a USB directly connected (e.g. model A).
The chips on the Raspberry-Pi are just not programmed to do that.
So, no keyboard or mouse...
And some folks need to stop being fanboys and see the forest behind the trees.
(One of the best lines I've seen on this board lately)
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Re: Naive question: Why have an sd card slot at all?
As I understand he means the BCM2835 has USB bootable capability but it's not coded into the PI to do so.
Even if USB booting was possible there's no way to connect a keyboard, mouse and LAN port since this would require a hub and as already stated you cannot perform USB booting via a hub.
Unless the PI has 2 USB controllers (which will never happen) USB booting is simply not possible.
Richard S.
Even if USB booting was possible there's no way to connect a keyboard, mouse and LAN port since this would require a hub and as already stated you cannot perform USB booting via a hub.
Unless the PI has 2 USB controllers (which will never happen) USB booting is simply not possible.
Richard S.
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Re: Naive question: Why have an sd card slot at all?
Regarding classrooms, if little Johnny deletes the OS from his card, and Susan comes in to the next class, she's using her own SD card, so Johnny hasn't caused her any problems. Cue discussion about the lack of IT support in schools to rebuild PC hard drives between lessons...
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Re: Naive question: Why have an sd card slot at all?
I think the "SoC can only boot from an SD card" is slightly wrong.
The SoC can only boot from flash memory connected to its bus that is built for that purpose. In a phone (or a set-top box), that would almost certainly be on-board flash. In the case of the Pi, there is no on-board flash...it's all on the removable card.
There is at least one similar tiny, single board computer (though not identical with respect to SoC) that has enough flash on it's PCB to boot from. For the Pi's intended use, this is less convenient.
(We need a generic term for "Pi like" computers... Pico-computers, perhaps?)
The SoC can only boot from flash memory connected to its bus that is built for that purpose. In a phone (or a set-top box), that would almost certainly be on-board flash. In the case of the Pi, there is no on-board flash...it's all on the removable card.
There is at least one similar tiny, single board computer (though not identical with respect to SoC) that has enough flash on it's PCB to boot from. For the Pi's intended use, this is less convenient.
(We need a generic term for "Pi like" computers... Pico-computers, perhaps?)