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

[hns]

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"?

I think he means uSD slot, socket, connector, reader etc.
The problem is that uSD uses only 4 data lines while eMMC has 8. So they are not compatible.

 

[Granitehead]

I think he means uSD slot, socket, connector, reader etc.

The problem is that uSD uses only 4 data lines while eMMC has 8. So they are not compatible.

I think so too, and my initial answer "It doesn't." assumed this, too.I'm aware that we would need a different (custom?) connector.

So, my question to you again:

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?

 

[WizardStan]

What about MMC mobile? It's a newer 8 bit bus width standard that's basically eMMC on a replaceable package, I think. Can't find anywhere to buy one though, all of my searches are returning "mobile" devices that use "mmc".

edit: nevermind, MMC mobile has max clock speeds of 52Mhz, we'd gain nothing.

This is why we'd want a replaceable eMMC, to get the 200Mhz speeds of the eMMC in a replaceable package.

 

[Grench]

The 128MB/s number I gave isn't a theoretical anything, that was measured. HardKernel claims 160MB/s. The measured speed can be artificially lower depending on access pattern and filesystem.

 

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.

Guys - the Toshiba microSD at 95MB/s is real.

http://www.tomshardware.com/charts/microsd-cards-2014/-1-Sequential-Read-MB-s,3480.html

96.2MB/sec if you want to get detailed.

If implemented right, that is. SDR 104 mode?

http://www.toshiba-memory.com/cms/en/products/microsd-cards/exceria/exceria-type-hd.html

 

[theredbaron]

Is there no way to get an SD to eMMC adaptor? As that seems to be what would be best. You can just put the emmc socket on the board, with the SD adaptor and a cheap 8gb SD. That way you can get the best of both worlds. You can easily upgrade for speed, or space, your choice.

Now I couldn't find one in a quick search, but as they are pretty close to the same standard, I would think that it wouldn't be hard to do and I just can't find it.

 

[Granitehead]

Is there no way to get an SD to eMMC adaptor? As that seems to be what would be best. You can just put the emmc socket on the board, with the SD adaptor and a cheap 8gb SD. That way you can get the best of both worlds. You can easily upgrade for speed, or space, your choice.

Now I couldn't find one in a quick search, but as they are pretty close to the same standard, I would think that it wouldn't be hard to do and I just can't find it.

I think such an adapter would need to be fabricated just for us. Would be easily electrically but not that easy mechanically. You could put an eMMC socket and an SD slot on the board and connect both to the same processor lines, but probably that would take too much board space. That would still mean you would need to produce custom eMMC modules/boards to make use of the eMMC socket.

 

[WizardStan]

Guys - the Toshiba microSD at 95MB/s is real.

I have no doubts that in a device capable of supporting it it can easily hit the 95MB/s.The OMAP5, however, has a maximum of 95MB/s, it cannot possibly go any faster under any condition. You are expecting that it will be able to reach this maximum speed guaranteed. If you can make that assumption then I'll make the assumption that an eMMC rated at 200MB/s will have no problem reaching the OMAP5's maximum speed of 192MB/s.

Will the port actually perform at max speed (in which case the eMMC should also perform at or near max speed) or will there be some kind of overhead that keeps it from going at full speed? In either case, the eMMC is still performing at about double.

I'll say it again, the 128MB/s for the eMMC is a minimum, reported by tests on the older ODroid, while the 95MB/s for the microSD is a maximum, reported by tests of dedicated SD hardware. The truth is somewhere in the middle, the eMMC will probably operate a little faster than the 128MB and the microSD will probably be a little slower.

You can just put the emmc socket on the board

eMMC isn't a socket, it's a type of chip that is soldered to the board. The eMMC supports an SD interface directly, no "adapter" is required other than the physical slot. The only way to "upgrade" an eMMC is if the chip is soldered onto a different board that will be plugged in, but that's up to ED and gta04.

 

[Granitehead]

You can just put the emmc socket on the board

eMMC isn't a socket, it's a type of chip that is soldered to the board. The eMMC supports an SD interface directly, no "adapter" is required other than the physical slot. The only way to "upgrade" an eMMC is if the chip is soldered onto a different board that will be plugged in, but that's up to ED and gta04.

I just understood it to mean the socket which accepts the plug which is soldered to the board onto which the eMMC chip is soldered. ;-)

 

[GizmoTheGreen]

Personally, if the SoC is capable. I would like eMMC for OS1. internal, hidden µSD slot for OS2(or to not use eMMC anymore)
and two external full size SD slots.

it's nice with bootable external SD but not really necessary, it only limits your "semi permanent" storage options. because honestly, who wants to have a USB stick always connected for storage if running OS from external SD1?

not me. 

It's up to what the SoC can handle, and if we must use SDIO for wifi (usb would be faster wifi throughput?)

 

[comradekingu]

I would rather boot of a usb stick than a uSD card since that is in the real world orders of magnitude better for OS use.

http://www.tomshardware.com/charts/2011-sd-cards/CrystalDiskMark-3.0-x64,2717.html

http://usb.userbenchmark.com/SanDisk-Extreme-USB-30-16GB/Rating/1301&tab=Review

A good usb drive with a real controller _crushes_ a good uSD

And that isnt even the http://www.sandisk.com/products/usb/drives/extremepro3/ which is said to do double digits 4k.

TL;DR If you only want to compare one number, make sure its 4k random read/write.

Edit: the poll is still biased towards modular emmc being the more costly option, just the ability is actually cheaper to implement. It does have some engineering involved, but you arent required to pay upfront for storage.

Use firstpost to explain everything. Delete all the votes and make it:

eMMC modular included storage accessible

eMMC modular included storage

eMMC modular unpopulated accessible

eMMC modular unpopulated (optional, not one for all)

eMMC included storage solderd to the board

(One size fits all vote) 8GB 16GB etc etc

uSD included storage accessible

uSD included storage

uSD unpopulated accessible

uSD unpopulated

Hotpluggable or behind the battery or wherever it is, is an engineering question, so we can do that later, this is just to gauge interest for modular and/or size options

 

[WizardStan]

I would rather boot of a usb stick than a uSD card since that is orders of magnitude better for OS use.

Explain? What makes USB better than microSD?

 

[SNESFAN]

How about a emmc, a microsd cage/connector, and a jumper? add/remove jumper to switch between a 8 pin emmc and 4 pin microsd?

Quick look around seems like the price is between $0.45 - $1.00/pc depending on quantity for the cage, no idea how much some small terminals and jumpers run but it can't be that much. Only issue I'd think would be pcb space for the extra traces and the connector.

http://www.mouser.com/ProductDetail/Molex/47219-2001/?qs=%2fha2pyFadugUlVGVkaKKEYsUTUSar9TNk9esopCDJtE%3d

 

[WizardStan]

A good usb drive with a real controller _crushes_ a good uSD

The microSD card Grench linked had real world rates of 70MB/s in random access reads.Meanwhile USB2.0 has a hard limit of 60MB/s under perfect conditions, conditions which are almost certainly not going to be met.

Grench's microSD card wins at speed by default, the only way for USB to beat the suggested microSD would be to use our one and only USB3.0 port, which means no outward facing USB3.0 and no slave: the products you linked all require USB3.0 in order to get their speeds and are therefore irrelevant.

edit: also please don't modify your post so much. If there is confusion just create a new post. Revisionism just causes further confusion.

 

[klapse]

I cannot imagine using even 8GB of rootfs on a pyra, if the games are available in PND format.

 

[theredbaron]

You can just put the emmc socket on the board

eMMC isn't a socket, it's a type of chip that is soldered to the board. The eMMC supports an SD interface directly, no "adapter" is required other than the physical slot. The only way to "upgrade" an eMMC is if the chip is soldered onto a different board that will be plugged in, but that's up to ED and gta04.

I just understood it to mean the socket which accepts the plug which is soldered to the board onto which the eMMC chip is soldered. ;-)

The only place I had heard of eMMC before is over at ODROID. I had thought that it was the whole thing that was the eMMC, not just the chip. They also have simple eMMC to TF adaptor's, so I thought it wouldn't be that hard to go the other way around.

 

[comradekingu]

Wizardstan: one of us is wrong, but here is the link http://www.tomshardware.com/charts/microsd-cards-2014/-8-Random-Write-4-KB-QD-32-MB-s,3487.html to where it does 0.34MB/s, worst case of all the 4k random tests, but at best it did 3.6MB/s read http://www.tomshardware.com/charts/microsd-cards-2014/-7-Random-Read-4-KB-QD-32-MB-s,3486.html 

A far cry from 70 and not anywhere close to the bus speed treshold.  Just because some solutions will have the bottleneck there, the real issue is these abysmal random results on uSD cards in particular.

Some complain that i reserve post, i do that rather than to quote the above poster. I often write my posts over 10-15 times when i longpost. There is no winning for everyone. And i dont consult the 5000 page TI manual as much as i should.

Right now im going back to correct not being able to run the whole os in tmpfs because i thought the limit was 2GB ram, i think that might be for the 5430, but i read today that its 8GB theoretical for 5432, which is the one poised for use. So potentially you could run everything in ram and boot from the cloud

Edit: couldnt find it, the "someone is wrong on the internet" is so much worse when you know its you

Edit2: here we go http://boards.openpandora.org/topic/15651-poll-updated-emmc-vs-usd-modular-emmc/page-4#entry314670

 

[WizardStan]

Writes will be happening so infrequently that it shouldn't be a consideration at all. Read speed is the only thing that matters and for 512K reads it is seeing 70MB/s.

But it still doesn't matter. Like I said, in order to get the USB access you want we'd have to sacrifice our USB3.0 OTG port and all the speed in the world isn't worth that exchange.

Some complain that i reserve post

Yeah, that's annoying too, because sometimes by the time you've gone back to edit your post several messages have already been made and whatever you said is lost.If you have to rewrite your post 10-15 times then take 10-15 rewrites before you hit "post", I don't see why you feel the need to have a placeholder just to edit it later.

 

[comradekingu]

Say you are opening a folder in a gui filemanager and its showing the thumbnails. I dont want the system to halt and chug along at turtlespeed just because its trying to make a database or best case read it to give me that functionality.

If the system is fast it makes sense for the storage to be fast, given that /home and the actual OS is the same resource here.  I know using the usb3 is a loss, but i would _rather_ that than to use uSD internal, when i could be using one of the regular SD cards. Its a slippery slope of what makes sense, and i think modular emmc everyone gets their cut. Maybe even hot swappable.

Or even a dual solution, but the emmc to SD card hardkernel option working on regular usb ports, isnt just a pin to pin ordeal. Im trying to get my head around SNESFAN solution. Will edit when i figure it out

If the mouser part has 8 connections. the mmc requiring 8, would have to share the 4 which SD card uses. And also you would have to make a emmc that fits the connector.

Part of the nicety about the hardkernel way is that you get the memory and the connector ready to go.

 

[WizardStan]

From the exact same link that you posted: http://www.tomshardware.com/charts/microsd-cards-2014/-8-Random-Write-4-KB-QD-32-MB-s,3487.html

There's a drop down labeled "Choose Benchmark", you can see random read (512K) in the list.

I have a directory with 122 files in it creating a total of 122 thumbnails ranging in sizes from 8k to 20k for a grand total of 2.5MB. Let's pick one of the middle benchmarks, 0.6MB/s for 4k writes gives us 4 seconds to write all those thumbnails, and it only has to do it once, hardly "chugging". The best of the USB solutions you proposed would still take 1 second to write those same thumbnails. Is that 3 seconds really worth the loss of our USB3.0 OTG port?

 

[comradekingu]

To me yes, and i think photographic use pictures are realistically 2.5MB+ jpegs (raw much larger), reduced to thumbnails of more than that size you specified, which is then a +4 sec ordeal every time, the 122 pics i agree on, and its not really random read iops, for good and bad.

I could probably argue the case that all my wonky needs and requirements say i need this and that, but its about choice. Of which we are all covered on the modular emmc train, because that makes sense for rich and poor, light and heavy use, etc. Speed goes up with more size, and that generally makes sense, but you cant have it all ways.

512K is huge chunks, much bigger than stripesize, which is relevant. If its prefetching, cache, this that or the other, we can agree that emmc is best, then usb (but is disqualified for other reasons, then SD (which should be used like normal when you have an internal option, which regular SD isnt)  then good uSD cards, last is bad  uSD cards,

Real life generic OS use bottlenecks is more important than whats in the top end of best case performance.

Being content at uSD means everyone else is excluded above that. Im saying modular emmc makes sense for all of us, because those 1MB/s uSD cards (which are the good ones) still cost a large amount of money while being inferior to regular SD (OS on SD shouldnt make more sense than internal from a performance point of view, but it does).  At the point where a uSD becomes even that inferior option, you can already afford 16GB modular emmc. And anything cheaper is just a bad option on a many hundred dollar device, which is to say those bad uSD cards should never be used for OS because they are just not meant for the task. General lagginess doesnt make sense to skimp in when its a lets say -20 dollar difference. And using 1 dollar on a connector means you can get orders of magnitude more performance than 1 dollar worth for free once the day comes to upgrade from the then, better options available.

eMMC doesnt work out of the box on a regular PC, but I dont see anyone removing their eMMC that often, and there even was the adaptor to use it with uSD connector on the PC, so uSD always loses for OS use and USB is a bad option.