[poll; updated] eMMC vs. uSD; modular eMMC

[vcoleiro1]

Enticing for sure, but the active power requirement of 2.7W is worrying, that seems a lot higher than the active power requirement of eMMC (about .66W from the one I looked up ie 200mA at 3.3V). Someone else might be able to do some more research and shed more light on this. Also the cost would have to be looked up - I'm guessing it's going to be prohibitively expensive, happy to be proven wrong though.


I think at the end of the day nano SSD will be ruled out due to price and or power consumption.


Now that ED has mentioned that there will be 2 USB 2.0 ports and one micro USB 3.0 port ie 5 removable and expandable storage slot options (2 SD + 3 USB flash drives) , it makes even less sense to lose the faster eMMC storage. I think if after all that you still want a uSD slot, lobby to get the SIM/uSD slot option happening.

 

[Natsu]

Flash drives are not an argument.

 

[vcoleiro1]

^ what ?

 

[Natsu]

^ what ?

You can compare flash drives to SD cards and eMMc. These are things that are in the device.Like I said, I'm not carrying a whole another device.

Let me put this way, put all those flash drives on and try to put it in your pocket.

 

[vcoleiro1]

Are you aware of how small flash drives are these days. You can easily get ones that only stick out 3mm from the USB port opening.

 

[bzar]

 

[_wb_]

Enticing for sure, but the active power requirement of 2.7W is worrying, that seems a lot higher than the active power requirement of eMMC (about .66W from the one I looked up ie 200mA at 3.3V). Someone else might be able to do some more research and shed more light on this. Also the cost would have to be looked up - I'm guessing it's going to be prohibitively expensive, happy to be proven wrong though.


I think at the end of the day nano SSD will be ruled out due to price and or power consumption.

If we take the SSD approach, power consumption and board size would be the main things to look for. I don't think price is that much of an issue -- for the same capacity, SSD will be slightly more expensive, but the difference does not seem to be huge.

This one:

http://www.innodisk.com/Product/ProductDetail.aspx?SUQwMT0wMDEmSUQwMj1lZTU5MTNlMC1iYTM5LTRkMDYtYWRmZi0zMzE4ZjVhMTU4YmImSUQwMz0mSUQ9ZTAzZmY3MzgtMGE4MS00MGU1LWFiNTItNDQyMjk1NWEwMTQzJmRmbF9JRD0wMDE%3d

has a max power consumption of 0.99W, can do 480MB/s reads and 175MB/s writes, dimensions are 16x20x2mm, which is more than eMMC (12x16x1.4 for SanDisk iNAND), but still reasonably small.

Something like that would be excellent. 4 or 8GB would probably be enough -- if you need more internal storage, just add a microSD card.

 

[vcoleiro1]

Well, you'll probably find that in the price list below,


http://www.jampel.it/Modules/ListFiles/Files/2013-03-12-02-55-59_IT.pdf

 

[_wb_]

Well, you'll probably find that in the price list below,

http://www.jampel.it/Modules/ListFiles/Files/2013-03-12-02-55-59_IT.pdf

According to that price list, these are the prices for nanoSSD:

nanoSSD 3ME (MLC, 480/90 MB/s sequential R/W):

$33.8 for 8GB (1ch), $47.8 for 16GB (2ch), $69.8 for 32GB (4ch), $133.8 for 64GB (4ch)

nanoSSD 3IE (iSLC, no specs on the innodisk website but probably the same as for SLC):

$63.8 for 8GB (2ch), $104.4 for 16GB (4ch), $179.8 for 32GB (4ch).

nanoSSD 3SE (SLC, 480/175 MB/s sequential R/W):

$33.8 for 1GB (1ch), $46.6 for 2GB (1ch), $81.2 for 4GB (2ch), $140.4 for 8GB (4ch), $254.6 for 16GB (4ch).

So yes, this is more expensive than eMMC, as expected. But it's also significantly faster.

Also note that the prices above are an upper bound -- that list is a few months old, and ED should be able to get a better price if he buys them in bulk and without a middle man.

If I understand the technology correctly, you need one that has 4 channels to get the fast speeds -- so the smallest sizes are not such a good idea. MLC has slower writing and less lifetime, iSLC is almost as good as SLC in terms of speed and lifetime (see http://www.slideshare.net/jessika_remolona/islc-technology), and SLC is the fastest, most reliable, and most expensive option.

So the best option is probably the MLC 32GB one (which costs at most 51 EUR), or the iSLC 16GB one (cost: 76 EUR), depending on how important writing is. I would probably pick the MLC one because that write speed and lifetime is still quite acceptable to me. However, if it is to be used for things like a swap partition, then iSLC or SLC is probably a better idea.

There are other companies that make tiny SSDs, you can probably find much cheaper ones if you don't mind lower speeds (e.g. the speeds you would get with eMMC). Here is an ugly page with maybe useful information: http://www.storagesearch.com/ssd-1p0.html

 

[Natsu]

Are you aware of how small flash drives are these days. You can easily get ones that only stick out 3mm from the USB port opening.

Those small ones can't have good speeds and it still adding size to the device.

 

[TrashyMG]

Are you aware of how small flash drives are these days. You can easily get ones that only stick out 3mm from the USB port opening.

Those small ones can't have good speeds and it still adding size to the device.

They have decent speed.. the real issue I see is keeping the USB host running all the time, it's a huge power drain.

 

[_wb_]

Do we need another poll? eMMC or µSD or µSSD or µSSD+eMMC or µSSD+µSD are the options given that the SoC has one SATA and one eMMC/SD available.

 

[Natsu]

NanoSSD 3ME 16GB seems good to me.

 

[_wb_]

Oops - nanoSSD uses SATA 3.0 (600MB/s interface), while OMAP 5432 only supports SATA 2.0 (300MB/s interface). So at best it is overkill and at worst it doesn't even work.

Having to restrict ourselves to SATA 2.0 means lower read speeds, but probably also cheaper prices. And still potentially 50% faster than the maximum for eMMC.

Here are some SATA 2.0 µSSD's: http://www.greenliant.com/products/?inode=48541

They are a bit slow ("only" 120MB/s reading and 80MB/s writing, there are probably eMMCs that can reach those speeds too), but they're supposed to be very reliable.

 

[Exophase]

_wb_, something you're not taking into consideration with these small SSDs is that they draw most of their power over 1.2V rails. I don't have a datasheet for TWL6037 but the EVM manual describes the power rails pretty adequately: http://www.ti.com/lit/ug/swcu130/swcu130.pdf (section 2.4) and you'll see there's no high power step down converter for 1.2V.

Also, the idle and sleep power numbers of the parts you gave (200mW and 70mW respectively) are pretty poor.

 

[Natsu]

Wait, we can't do eMMC+uSD?

 

[_wb_]

_wb_, something you're not taking into consideration with these small SSDs is that they draw most of their power over 1.2V rails. I don't have a datasheet for TWL6037 but the EVM manual describes the power rails pretty adequately: http://www.ti.com/lit/ug/swcu130/swcu130.pdf (section 2.4) and you'll see there's no high power step down converter for 1.2V.


Also, the idle and sleep power numbers of the parts you gave (200mW and 70mW respectively) are pretty poor.

OK, so let's not take the Greenliant ones.

I assume there are small SSDs that use 3.3V only (like the innodisk nanoSSD?), have lower idle/sleep power consumption, and use SATA 2.0. Maybe RunCore rSSD? (http://www.runcore.co/en/RC-SSDProductShow-245.html)

 

[hns]

Yes, the Greenliant chip look nice in the first step, but it appears to be difficult to source them:

http://octopart.com/partsearch#!?q=GLS85LS1016P

Don't stumble over the prices mentioned there - it appears to be for the EVM.

There is a link to a data sheet:

http://datasheet.octopart.com/GLS85LS1016P-S-I-FZJE-ND101-Greenliant-datasheet-13555848.pdf

Indeed they need a 1.2V supply and a separate 25 MHz xtal. And they are a little spacy (24 x 12 x 1.9mm). That is much more volume than a uSD card...

Finally: "Current product revision will only support SATA Revision 1.x with host transfer rate of up to 1.5 Gb/s (i.e. SATA 1.5 Gb/s). SATA 3.0 Gb/s refers to SATA Revision 2.x and is planned to be supported by our future product revisions."

Generally I like the idea to make the eMMC port available for other purposes (extra uSD) and connect something to the SATA port - but it looks as if it drives us into the dependency of niche suppliers.

 

[_wb_]

Wait, we can't do eMMC+uSD?

No, not both at the same time. Unless you want to sacrifice one of the fullSD slots. That's why I think it makes sense to have a µSSD (using the SATA interface which would otherwise not be used at all) and a µSD slot for optional extra internal storage. I don't think µSSD + eMMC makes sense, no point in having two different kinds of non-upgradeable internal storage.

 

[hns]

Wait, we can't do eMMC+uSD?

The OMAP5 has 4 SD/SDIO/MMC ports. We want to use one for eMMC, two for the standard SD slots and one for SDIO for the WiFi. So there is nothing left over. Connecting WiFi over USB is a potential option - but there are no easily available BT/WiFi combo chips with USB for the WiFi side. They almost always use SDIO. So by solving one end we have just moved the problem to the other
Believe me, designing a device like the Pyra is a quite complex puzzle... And it is impossible to make everyone happy, especially if we also take dimensions, battery life and price into account.

Nevertheless it is really interesting to learn about new options. And we may be lucky to find a better global optimum.