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In Reply to: RE: I disagree with you and agree with Sprezza Tura posted by Thorsten on October 18, 2014 at 12:12:18
Oh but it were so simple.. :-) That SD card itself already is a computer, albeit a minimal one. SD cards can be hacked. However, it's definitely a very low power computer and its small size probably makes it a poor radiator.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Follow Ups:
Tony,
SD Cards contain a Microcontroller (usually 8 Bit 8051) for some housekeeping jobs. They operate synchronous with the card operation.
Past that an SD card is just a giant serial flash memory chip. Reading is fully synchronous. All in all an SD Card makes a fine facsimile of a CD in mst areas of operation.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
I'm not familiar with the instruction set of the 8051, but I am familiar with the similar 6502, which was the processor in the Apple II personal computer. I even programmed it to do digital signal processing (LPC compression of telephone quality voice), and this worked after a fashion, but the processing ran at 10 times slower than real time after I speeded up my original Basic code by changing the data encoding, rewriting the math library routines and doing all the processing in assembler. The 64 kb RAM allowed storage of only a few seconds of voice. My friends and I built a sound card out of a free sample 64 kb Motorola CODEC chip. This was around 1980. I also made the Apple II speaker (connected to a programmable flip-flop) play a mix of square waves of two different frequencies by using pulse density modulation.
While the SD card runs in one clock domain, I'd be surprised if the number of clock cycles required per data transfer is fixed. I'm certain that is not the case when it comes to writes, which can become very slow, particularly if the card has a lot of wear from many writes. I use one of these SD cards with my Raspberry Pi, and I have gone through about six cards in 18 months due to wear-out, from doing system updates, etc..
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Tony,Nothing stops you fixing the clock...
I cannot say I had any flash memory fail on me (despite being machine - washed in my trouser pockets), but my normal use of Flash memory is VERY static (I almost use them in WORM mode), except in my Digital Camera, but even there I tend to pile pictures untilnearly full, then I copy them off and after that format the card.
8051 based MCU are the mainstay of primitive embedded systems, think Fridge, CD-Player etc. and I have used them quite a bit. Though for my recent designs I have switched to ARM2 based Freescale Kinetis 32 Bit processors, which are incredibly more flexible and competetive price wise.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
Edits: 10/19/14
Are they, and their receptacles shielded? How good is the power supply to them. How big do they need to be in capacity for a system that is convenient to use? What is the price of a 256G card? How do know know before buying that they work as claimed?
For a 256G SD card, I can buy a much larger ssd; may be 1.8 in although these are a nuisance as well by way of some connectors.
This is indeed fascinating. What are the ways that one could realistically be vulnerable or harmed? I only use SD cards for my portable digital recorder and digital cameras.
The main take-home is that these cards can hold hidden information that can not be discovered by the user using only normal access to their pins. This means:
1. If they contain illicit material or malware, they may retain this unwanted information after you think you have "sterilized" the card. This information may remain accessible to anyone who knows a secret code, but otherwise inaccessible by a normal user.
2. This capability makes it easier for the card to serve as a vector for malware or spy ware, etc...
3. If you do not trust the supply chain for the card or if the card has ever been connected to an untrusted computer then it is not to be trusted, and should not be connected to any computer that you wish to continue to trust.
Of course, this depends on how paranoid you are, what information you have and who might want to know it, if you are a person of interest, etc... Probably not a problem for cards used in computers that are never used for anything but audio, but if you have a file server that holds personal material as well as music then there may be a risk.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Thanks for the information.
I guess we have to define a person of interest.:)
Wow! I'd never really considered that. Stupid I suppose but somehow even knowing about wear leveling and defect detection and correction didn't quite ring the bell that there might be a hackable controller on board.
Obviously time to take the dog for a walk, that seems safe and untechnical. Now where's my cell phone...
Rick
I am more concerned with the fact that many won't work reliably in PCs and some can't even be formatted in ntfs.
They seem to work more reliably in cameras.
I have to heavily junk my inbox against sd card and usb thumb drive promotions as I am now very discerning about what removable media devices I buy.
By coincidence, I discovered that SLC thumb drives work best and fastest.
My Raspberry Pi runs off an 8 GB micro SD card. After too many failures I switched to the more expensive cards. These seem to be somewhat better. Operating system updates and software builds are particularly hard in terms of write overhead. Running my embedded system is not a problem, because it is designed to write very little data to the card, and that only on system shut down.
Based on my track record with smaller cards, I'm not likely to shell out the money for a larger SD card. It probably would work OK for holding a small library of reference tracks, but to use it to shuttle daily listening music seems risky, in addition to inconvenient as you pointed out earlier.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Class 10, Ultra, 45MB/s are just labels. In reality none of these shape up to claims and this is buying from major names and large retailers.
Some cards just don't like PCs and Windows. I actually think that it is the controllers which are not sorted.
There are many cheapish Chinese SD card players but there is no telling what player software is embedded. I may try a few at shops when I visit and see what they can do. It is still unwise to pay for large cards for hires music.
On my modified Korg MR1, I actually chose to use a 1.8 in ssd and not a sd card because of the number of modders who had trouble getting them to work with brands other than Photofast .
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