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

[destraht]

I really think the poll should feature a removable eMMC ala hardkernel option, for which there isnt a price premium, since you dont have to populate it and it can be added in by the user later on.

Paying less up front, for having options down the road, and a device less likely to wear out, is what i would vote for. Depends what one would sac for the space needed if it came to it.

I would be satisfied with even 8GB if I could replace it with a faster 32GB one in a few years.  Regardless the Pyra is going to hit my pocket book pretty hard and for me just having one to begin with will be most important.

 

[destraht]

This poll has been showed to be flawed since apparently replaceable eMMC memory is available.  I would love to spend $5 on a eMMC socket to save $30 on cheaper chip, and then to be able to upgrade later.  I don't know about anyone else but spending $100 on an off-purchase year never hurt me that badly.

 

[Klumpen]

Replaceable eMMC memory would be a compromise indeed, if the board design allows it.

 

[Trickyhero]

I vote for the cheapest, considering most people will be using external sd cards also we could use a smaller storage thing inside of the pyra, 8gb should definitely fit the OS.

 

[comradekingu]

The cheapest is none, or unpopulated uSD or removable eMMC. Which if made an option, ideally calls for it to be serviceable without unscrewing anything.

 

[destraht]

The cheapest is none, or unpopulated uSD or removable eMMC. Which if made an option, ideally calls for it to be serviceable without unscrewing anything.

It seems to me that is quite a strict requirement.  I'd hope for something as easy as operating on a Thinkpad.  I'm not hardware genius and I can very easily remove screws to change RAM, HD, keyboard and touchpad.  I think that it would be a mistake to base the design around being able to save 5-10 minutes to change out a SSD once or maybe twice over the life of the device.

 

[_wb_]

At these speeds (well over 50MB/s whatever option is chosen), size, reliability and future-proofness are more important than extra speed. Boot time should be very short anyway -- it's not that bad on my Pandora booting from SD, with a read speed of only ~15MB/s and a way slower SoC. Compared to a spinning HDD, latency / seek times are similar between eMMC and µSD: very good. Once booted, most of the OS is in RAM anyway. I don't think the difference between 80MB/s and 160MB/s would really be noticeable. The difference between and 2x is always quite noticeable though .


 


On the Pandora I sacrifice one SD slot (and don't use the NAND at all) just to have no space limitations. Even if the Pyra comes with a large eMMC, there will be a point in time when that is not going to be enough for someone. Keep in mind that we plan to use a normal GNU/Linux distro and install most of the normal software using the normal package manager of the distro on the internal storage. People may also want to put some game PNDs and data on their internal storage.


 


If we use a fixed-size eMMC, we either have to pay a lot now to make sure that it is as fast and big as possible, or we keep costs down and are stuck with some limitation forever. With µUSB it suffices to ship a cheap 8GB card and leave it up to the user to upgrade it if he needs more speed or size. It would also be easy to ship it with different sizes of cards or even without any card at all.


 


Replaceable internal storage is a really nice feature (even if replacement requires a screwdriver). It means you can use the internal storage for data without having to worry about space or wear levels. A couple of fullHD movies will quickly fill any storage medium. Imagine being able to upgrade your Pyra to 256GB of internal storage in a few years. Now imagine being stuck with 2GB forever (because that is what 8 or 16GB will probably "feel like" in a few years).


 


Dual SD slots already make the Pandora and Pyra future proof. Replaceable internal storage would make the Pyra even more future proof.

 

[Granitehead]

This poll has been showed to be flawed since apparently replaceable eMMC memory is available.  I would love to spend CHF4.65 ($5) on a eMMC socket to save CHF27.87 ($30) on cheaper chip, and then to be able to upgrade later.  I don't know about anyone else but spending CHF92.90 ($100) on an off-purchase year never hurt me that badly.

I was aware of replaceable eMMC when I created the poll. Read the first post again.


It says this (emphasis new):

It's in theory possible to get replaceable eMMC, but I think the consensus of the discussion was that it can't be obtained easily enough and it's supply isn't guaranteed for long enough. That's why I didn't include it. If it was readily available, I think most people would agree it's the best solution unless it adds to the cost a lot. But that's just irrelevant speculation.

Hardkernel alone selling it doesn't mean "readily available".

I think probably ED would need to create his own module. That would certainly raise cost. We don't know how much. Probably not by a huge amount, but we don't know.

But I'm adding another question to the poll, wait.

 

[WizardStan]

I just did some benchmarks on the NAND of my Pandora and was consistently getting around 10MB/s reads. Even if the 95MB/s microsd card can only sustain 64MB/s on the Pyra it's still 6 times better than what we have now. I'm starting to think that eMMC speeds are overkill.

edit: scratch that, it only holds true when I was testing small files. Testing larger files, 40+MB, I'm getting around 250MB/s sequential reads.

Hrm... This seems very wrong.

edit edit: doh, forgot the memory cache. With the memory cache dumped reading large files falls back to 50MB/s.

 

[_wb_]

I just did some benchmarks on the NAND of my Pandora and was consistently getting around 10MB/s reads. Even if the 95MB/s microsd card can only sustain 64MB/s on the Pyra it's still 6 times better than what we have now. I'm starting to think that eMMC speeds are overkill.


edit: scratch that, it only holds true when I was testing small files. Testing larger files, 40+MB, I'm getting around 250MB/s sequential reads.


Hrm... This seems very wrong.


edit edit: doh, forgot the memory cache. With the memory cache dumped reading large files falls back to 50MB/s.

Interesting results. So with a fast microSD card it would still be about twice as fast as the NAND of the Pandora (and about six times as fast as SD cards on the Pandora). With the fastest possible eMMC it could be twice as fast as microSD in theory, but probably not in practice at this point in time (because eMMC that maxes out the theoretical speed is not yet available or too expensive).

Replaceable eMMC has in general the same advantages as replaceable microSD. It has the additional advantage that it can be faster, but it has the disadvantage that it is harder to find a replacement eMMC (you can buy a microSD card anywhere).

 

[Granitehead]

I just did some benchmarks on the NAND of my Pandora and was consistently getting around 10MB/s reads. Even if the 95MB/s microsd card can only sustain 64MB/s on the Pyra it's still 6 times better than what we have now. I'm starting to think that eMMC speeds are overkill.

edit: scratch that, it only holds true when I was testing small files. Testing larger files, 40+MB, I'm getting around 250MB/s sequential reads.

Hrm... This seems very wrong.

edit edit: doh, forgot the memory cache. With the memory cache dumped reading large files falls back to 50MB/s.

 Interesting results. So with a fast microUSB card it would still be about twice as fast as the NAND of the Pandora (and about six times as fast as SD cards on the Pandora). With the fastest possible eMMC it could be twice as fast as microUSB in theory, but probably not in practice at this point in time (because eMMC that maxes out the theoretical speed is not yet available or too expensive).

Replaceable eMMC has in general the same advantages as replaceable microUSB. It has the additional advantage that it can be faster, but it has the disadvantage that it is harder to find a replacement eMMC (you can buy a microUSB card anywhere).

s/USB/SD/g ;-)
I added a poll question, do you think I found the right one to ask? I'm assuming ED would need to produce the modules himself, wouldn't he? There are no (solderless) eMMC modules available?

 

[_wb_]

I just did some benchmarks on the NAND of my Pandora and was consistently getting around 10MB/s reads. Even if the 95MB/s microsd card can only sustain 64MB/s on the Pyra it's still 6 times better than what we have now. I'm starting to think that eMMC speeds are overkill.


edit: scratch that, it only holds true when I was testing small files. Testing larger files, 40+MB, I'm getting around 250MB/s sequential reads.


Hrm... This seems very wrong.


edit edit: doh, forgot the memory cache. With the memory cache dumped reading large files falls back to 50MB/s.

 
Interesting results. So with a fast microUSB card it would still be about twice as fast as the NAND of the Pandora (and about six times as fast as SD cards on the Pandora). With the fastest possible eMMC it could be twice as fast as microUSB in theory, but probably not in practice at this point in time (because eMMC that maxes out the theoretical speed is not yet available or too expensive).


Replaceable eMMC has in general the same advantages as replaceable microUSB. It has the additional advantage that it can be faster, but it has the disadvantage that it is harder to find a replacement eMMC (you can buy a microUSB card anywhere).

s/USB/SD/g ;-)

I added a poll question, do you think I found the right one to ask? I'm assuming ED would need to produce the modules himself, wouldn't he? There are no (solderless) eMMC modules available?

Ugh, I spent too much time in the full-USB vs microUSB thread

I don't know anything about replaceable eMMC. Isn't a replaceable embedded MMC just an MMC again?

 

[Granitehead]

I don't know anything about replaceable eMMC. Isn't a replaceable embedded MMC just an MMC again?

Well, if you ask like this, yes.The difference is that a replaceable MMC chip would be soldered to a small daughter pcb instead of the mainboard. That daughter PCB would have a connector which fits into a connector which is soldered to the mainboard.

 

[hns]

If I remember right, gta04 said, the OMAP5 can only handle one eMMC and one SD slot, a second SD slot has to be added with a separate usb-sided controller. So why should we "loose" one SD port, if we add uSD instead of eMMC? There would be only one SD port anyways if they don't add the controller.

The conversion between eMMC and SD isn't so complicated, so we could use uSD via the eMMC port.

About the possible speed using this kind of system I really don't know much about. But I don't think the max possible speed would decrase a lot (on bus side).

EDIT: In my opinion we should take the uSD slot. User modification would be as easy as possible, and who really minds ~30MB/s more or less if we're already talking about ~100MB/s standart speed? Anyways it would be fast

OMAP5432 mmc ports:
mmc1: 8 bit eMMC capable (can boot)

mmc2: first SD slot (can boot)

mmc3: SDIO for WiFi

mmc4: second SD slot (can't boot)

mmc5: second 8bit eMMC (can't would only available on OMAP5430 package which is not available)

So if we can have either Micro-SD or eMMC on port SD1.

And note: Micro-SD provides only 4 data wires - therefore half the speed of a 8 wire eMMC at the same clock rate.

Well, one option would be to have a Micro-SD on SD1, an eMMC on SD2 and operate the Standard-SD slots through an USB card reader chip.

If there is going to be a 3g module in it - then we'll need end users to be able to access the SIM card. A microSD shouldn't need to be any more difficult.

Yes, we already had discussed that a while in the team.

As far as replacing the microSD, to really be as user friendly as possible it'd probably be best to keep it under the battery just so it guarantees the power is off before they go mucking with their operating system drive but I'd be interested in some counterpoints.

Agreed, that definitely does make the most sense. I'm fine with having it anywhere that's reachable, (side of the device, under the battery) and preferably somewhere where I don't have to use a screwdriver to get to it. But putting it under the battery will be the best way to prevent complaints from idiots about their card getting corrupted, or their system doing strange things, or so forth.

Yes-

Interesting results. So with a fast microSD card it would still be about twice as fast as the NAND of the Pandora (and about six times as fast as SD cards on the Pandora). With the fastest possible eMMC it could be twice as fast as microSD in theory, but probably not in practice at this point in time (because eMMC that maxes out the theoretical speed is not yet available or too expensive).

That matches the experience with the GTA04 (which has the same DM3730+PoP-RAM/NAND as the OpenPandora). NAND booting is slower than from a Class 10 uSD.
BTW: if you look at my logo picture you will see such a combined SIM/SD reader in the upper left area (between the two gold connectors). Or better visible here:

http://www.goldelico.com/images/gta04-0033.png

 

[hns]

I don't know anything about replaceable eMMC. Isn't a replaceable embedded MMC just an MMC again?

Well, if you ask like this, yes.The difference is that a replaceable MMC chip would be soldered to a small daughter pcb instead of the mainboard. That daughter PCB would have a connector which fits into a connector which is soldered to the mainboard.

Well, inside of a SD/uSD card there is also some memory chip soldered onto a small PCB. And finally it is covered by black plastics.
Or in other words: a replaceable eMMC is a SD with slightly different protocol which supports a higher speed.

If I remember correctly the MMC standard was first. Then, SD was invented as an extension. And some clever person in the marketing department of some flash memory manufacturer coined the name eMMC. And then, two almost identical standards and interfaces exist.

 

[Granitehead]

I don't know anything about replaceable eMMC. Isn't a replaceable embedded MMC just an MMC again?

Well, if you ask like this, yes.The difference is that a replaceable MMC chip would be soldered to a small daughter pcb instead of the mainboard. That daughter PCB would have a connector which fits into a connector which is soldered to the mainboard.

Well, inside of a SD/uSD card there is also some memory chip soldered onto a small PCB. And finally it is covered by black plastics.
Or in other words: a replaceable eMMC is a SD with slightly different protocol which supports a higher speed.

If I remember correctly the MMC standard was first. Then, SD was invented as an extension. And some clever person in the marketing department of some flash memory manufacturer coined the name eMMC. And then, two almost identical standards and interfaces exist.

I'm aware of the similarities.But as we might want to take advantage of that higher speed, replaceable eMMC would still be nice.

Do you know how much cost this would add to implement at all and then how much each additional type of repaceable eMMC would add?

Or is it maybe possible to buy replaceable eMMCs? Other than from Hardkernel which probably can't be considered to be enough to guarantee supply?

 

[God Ginrai]

I added a poll question, do you think I found the right one to ask? I'm assuming ED would need to produce the modules himself, wouldn't he? There are no (solderless) eMMC modules available?

I don't seem to have a way to express that I would want replaceable eMMC if we couldn't get microSD, but only in that case.

-God Ginrai

 

[SNESFAN]

^if replaceable emmc uses a microsd cage? kind of defeats the purpose I suppose

 

[Granitehead]

I added a poll question, do you think I found the right one to ask? I'm assuming ED would need to produce the modules himself, wouldn't he? There are no (solderless) eMMC modules available?

I don't seem to have a way to express that I would want replaceable eMMC if we couldn't get microSD, but only in that case.

-God Ginrai

Hmm, this is a flaw in my question, thanks.

^if replaceable emmc uses a microsd cage? kind of defeats the purpose I suppose

It doesn't.
Edit: Or what exactly do you mean with "cage"?

 

[SNESFAN]

^ maybe I'm using incorrect terminology

http://www.molex.com/product/memory/microsd.html