Replace one SDXC with internal USB3?

[Binky]

First off: This is not about fullSD vs microSD - there are threads full of discussion of that and most people have had their say already.

Suppose the P2 were to have two SDXC slots in a similar way to the P1

Now suppose that it had one SDXC slot and one internal (full-size) USB3 port - in addition to an external one.

USB3 speeds are supposed to be 625MB/s compared to 300MB/s with SDXC (no idea if these speeds will be achieved in practice)

(do note the capital 'B')

USB3 ports are slightly smaller in terms of PCB footprint, but are much taller and (may) need fancy supporting hardware. Space would also nee to be made for the USB device itself, which could be a smallish USB stick.

It could also be all sorts of other cool stuff - perhaps you could use protruding usb dongles with a little clever case design

Perhaps a slightly narrower (right-to-left) battery would make room for a superspeed USB stick

So advantages of swapping an SDXC slot for a second USB3 port:

• much more versatile
• possibly twice as fast (good for booting off)
• Smaller PCB footprint

Disadvantages:

• fiddlier case design
• might make the P2 thicker
• suitable USB devices might be limited

Thoughts?

 

[thatgui]

I wonder how power consumption compares. I would recommend also only using real USB3 devices as using USB2 devices would mean constant cpu load.

 

[hedwards]

I'm not sure I understand the point of this. Most data for the P2 is going to be on SD cards and unless SD cards grow by an unimaginable amount in the next few years, you're not going to save any time by going USB3 over USB2.

Now, if the P2 had a large internal HDD, then it might make sense.

 

[Mr_Loon]

You won't be surprised to hear that I completely agree with you (see the price and specs section of the first post here)

Having a USB3 stick instead of the Nand would bring many obvious benefits to customers and make the PCB manufacturing process more simple and less costly.

The negatives would be that it could increase power drain (does a USB3 stick drain more power than a NAND on the PCB?) and could increase the thickness of the case to accommodate the USB3 connector + stick.

IMHO the benefits far outweigh the negative aspects.

My question to you would be : Why replace a SDXC slot for the USB3 'Nand' when you could have 2 X SDXC and the USB3 stick  Nand replacement?

 

[Binky]

I'm not sure I understand the point of this. Most data for the P2 is going to be on SD cards and unless SD cards grow by an unimaginable amount in the next few years, you're not going to save any time by going USB3 over USB2.

Now, if the P2 had a large internal HDD, then it might make sense.

Surely if an internal USB3 stick were twice as fast, some people would use that in preference to SD cards.

--

@ Mr Loon: The P1's NAND is in a POP assembly isn't it? If so rather more board space would be required to fit in a second USB port.

Having said that, making the P2 12mm wider would easily solve the space  problem

Twin SDXC + internal USB3 would be brilliant.

 

[mcobit]

Wouldn't an usb stick need to be powered constantly?

My batteryusage is increased when I have a usbstick plugged into my Pandora.

 

[Askarus]

Wouldn't an usb stick need to be powered constantly?

My batteryusage is increased when I have a usbstick plugged into my Pandora.

Also my estimation.

Enable USB (even without an USB stick inside) and you don't want to have one internal stick that needs to be switched on all the time.

 

[Mr_Loon]

Wouldn't an usb stick need to be powered constantly?

My batteryusage is increased when I have a usbstick plugged into my Pandora.

 Also my estimation.

Enable USB (even without an USB stick inside) and you don't want to have one internal stick that needs to be switched on all the time.

does a USB3 stick drain more power than a NAND on the PCB?

 

[Drammurt]

I'd prefer an internal swapable eMMC-card like the Odroid-X2 has implemented. eMMC is an industry standard for high speed internal memory with built in error correction, wear leveling and bad block management. Unlike SD-cards and USB flash drives eMMC is designed to function as internal memory and because of that more suitable.

The amount of internal space needed for an USB-stick to fit in the case is enormous. To fit the better sticks like Transcend JetFlash you'd need at least 20 cubic cm of "empty" space and still a lot of sticks wouldn't fit or require modifications. Also there are a lot of crap sticks and sd cards out there with "magic up to xxx MB/s "-numbers that are based on large file sequential reads and writes which are quite meaningless when functioning as internal storage.

Making it swappable on a small PCB and by implementing the eMMC-standard ppl could later upgrade to faster and more memory. The (consumer) prices on hardkernel.com are not too shabby 8GB for $21, 16GB for $35 and 64 GB for $75 for a eMMC module that is twice the speed of a class10 SD card.

Samsung introduced new high performance eMMC memory with transfers up to 140/50 MB/s and 3500/1500 IOPS. If you look at the IO performance or small reads and/or writes of the better USB3-sticks you'll see why you don't want an USB stick as main storage.

My 2 cents.

 

[Mr_Loon]

Hey Drammurt, that sounds like a superior solution.

If it uses less power & less space & works faster, I'm going to incorporate that into my P2 concept.   
 

Paying just $10 more than you would for the equivalent USB stick the 16GB version seems like value IMHO.

 

[hedwards]

I'm not sure I understand the point of this. Most data for the P2 is going to be on SD cards and unless SD cards grow by an unimaginable amount in the next few years, you're not going to save any time by going USB3 over USB2.

Now, if the P2 had a large internal HDD, then it might make sense.

Surely if an internal USB3 stick were twice as fast, some people would use that in preference to SD cards.

I don't believe that USB sticks saturate USB2 bandwidth at the present, and would you really want to have a USB drive sticking out of your P2 that often?

I have a hard time thinking of things that you could do with USB3 in this case that USB2 would do just as well. I think video out is probably the only thing I can think of. And unless you drop proper video out for it, even that doesn't make sense.

 

[thatgui]

Wouldn't an usb stick need to be powered constantly?

My batteryusage is increased when I have a usbstick plugged into my Pandora.

The USB2 controller is constantly polling for new messages which leads to a constant cpu load which in turn leads to higher power consumption as neither cpu nor USB2 controller can enter a sleep mode. Afaik a USB3 controller is not pollling anymore and can enter different sleep states to save power (only if you connect real USB3 devices, of course).

But my guess is that a USB3 device + controller will drain a lot more than an sdcard or the nand.

I'd prefer an internal swapable eMMC-card like the Odroid-X2 has implemented. eMMC is an industry standard for high speed internal memory with built in error correction, wear leveling and bad block management. Unlike SD-cards and USB flash drives eMMC is designed to function as internal memory and because of that more suitable.

sounds a lot more reasonable than an internal USB3 port.

Edit: This could also lead to different P2 - models, having maybe a cheaper "low end" 8GB P2 or a "high end" 32/64/x GB P2

 

[3_bit]

That would be a very viable solution. I haven't exactly seen any SSDs small enough to be practical for the OP. I think an internal card slot (MicroSD might work best(I am aware of it's limitations, but real estate is limited)) would be better with an external USB3.

 

[Binky]

I was suggesting both internal and external USB3 - and I can guarantee that USB3 memory sticks will become smaller.

How much smace would have to be allowed? I don't know, but the possibilities for hacking and adding functionality are (potentially) huge.

 

[_wb_]

The problem with internal USB is that it's a power drain if you're constantly using it, and it's a waste of space if you're not constantly using it. So I don't think it's a good idea.

eMMC sounds quite good, are there any (passive?) adapters that let you use an eMMC card in an SD slot? (at lower speed of course)

I can see why eMMC would be a better idea than internal microSD, but the advantage of microSD is that you can easily put it in an SD slot with a passive adapter. It's nice if all storage can be easily interchanged, e.g. suppose I have a 8GB internal storage and upgrade to something bigger, then I can still use the old microSD card, but with eMMC it might be harder (I dunno) to reuse it.

 

[thatgui]

...and I can guarantee that USB3 memory sticks will become smaller.

how / why ?

 

[Binky]

^ USB3 sticks are essentially chips-in-boxes, and chip fabrication keeps on becoming more compact.

 

[overgauss]

Some numbers as I recall:

The fastest usb 3.0 flash drive has a max sequential write of about 170 MB/s

"               " eMMC "                                                                         " 50 MB/s
"               " microSD"                                                                       " 95 MB/s

But this discussion all depends on how fast the SoC can access/transfer to and from disk storage. In short, it may be the SoC's memory controller that is the actual bottleneck and not the memory itself.

Edit: max

 

[thatgui]

^ USB3 sticks are essentially chips-in-boxes, and chip fabrication keeps on becoming more compact.

But that does not necessarily mean that the sticks itself get more compact. Its more likely that you just get more capacity but the size of the stick itself is kept roughly the same - at least thats what I think I have observed over the last ten years.

Some numbers as I recall:

The fastest usb 3.0 flash drive has a sequential write of about 170 MB/s

"                      " eMMC "                                                         "    50 MB/s

"                     " microSD"                                                       "    95 MB/s

But this discussion all depends on how fast the SoC can access/transfer to and from disk storage.  In short, it may be the SoC's memory controller that is the actual bottleneck and not the memory itself.

I think that not only datat ransfer rates should be taken into consideration when its about choosing the "right" storage medium. I would also consider power consumption as of equal importance as transfer rates - I'd rather live with a slower type if it gives me more independence from a wall socket (as at least 75% I would not notice the difference anyway).

 

[ttxman]

eMMC sounds quite good, are there any (passive?) adapters that let you use an eMMC card in an SD slot? (at lower speed of course)

odroid have microSD adapter bundled with their emmc modules

Some numbers as I recall:


 ....

I think that not only datat ransfer rates should be taken into consideration when its about choosing the "right" storage medium. I would also consider power consumption as of equal importance as transfer rates - I'd rather live with a slower type if it gives me more independence from a wall socket (as at least 75% I would not notice the difference anyway).

Problem with MicroSDs with class above 6 is their random read/write perfomance, because they are tuned to act as a storage to the HD video recording cameras(phones) = sequential read and writes

My 8GB microSD class 10 have about 20 random (4k)writes per second

Notebook mechanic HDD have about 90

Samsungs eMMC modules have 2000

UHS-1 microSDs are faster but not by order of two magnitudes

I realy don't see point in writing more than 50MB/s to internal storage (= system disk), but improving system response hundredfold seems awesome..

USB3 disks with high speeds are complete SSD disks with 4-8 modules each with size bigger than 2 microSDs (and thicker), this is no go for pocket device. And if you search the google a little bit you can found numbers like 1W idle /5W active power consumption - And Pandora's battery capacity is +-15Wh with upscaling to 5V fast USB3 flashdrive would drain it in few hours alone.

And out of curiosity - sandisk eMMC datasheet: (old one from 2010 - EMMC with sustained read/write 15/9 MB/s ) 

Automaticaly entered sleep mode 0.001W (3.3V, 350uA)

Typical consumption during sleep (suspended device) 0.0003W (3.3V, 110uA)

Typical consumption during high speed read/write: 0.66W (3.3V, 200mA)

USB3 Internal storage is very very very bad idea