6 ms·

Having eMMC support is a game changer over a microSD card. It makes it feel like a real computer.

by mgulick 6y ago

rjsw 6y ago
The ODROID-C2 has eMMC, doesn't feel as fast as the eMMC drive on another AArch64 machine that I have though.
- mgulick 6y ago
  Maybe, I don't have another eMMC board to test with, but compared to my RPi 3 with an SD card, the eMMC feels way faster. Very noticeable doing an apt upgrade. Note I use all of my boards headless.
zozbot234 6y ago
A microSD card is just MMC that's socketed instead of being soldered to the package/board. It's good for flexibility. With 4GB RAM, performance should be a non-issue either way.
- myself248 6y ago
  ....over a narrow bus, and with controllers that have to make assumptions about power being yanked at any moment so they can't do proper SSD-like things that eMMC chips can do.
  - vardump 6y ago
    Narrow bus? I think current SD card standards can go way past 1GB per second (note: see edit below). It's an implementation detail. In practice, these cheap boards will have a cheap eMMC soldered in that can't do these fancy things anyways. It's not going to be same quality chip like in flagship phones. Once that cheap eMMC fails, the device is bricked. Edit: SD card standards still can't go past 1 GB/s, max 985 MB/s. Either way, plenty for cheap SBCs.
    - zwieback 6y ago
      narrow as in bit width
      - vardump 6y ago
        So blame the bad narrow implementation?
        zwieback 6y ago
        Not taking sides, just trying to clarify. I think there's a place for eMMC and SD but you're right chip quality and controller implementation is key.
    - zozbot234 6y ago
      I don't think even flagship phones have "quality chip" inside. Phone OS's are still running without swap memory support to cope with poor quality of their onboard eMMC (which leads to OOM-killing "background" apps instead of just swapping memory out.)
      - snalty 6y ago
        iPhones use NVMe storage and have done since the iPhone 6S and the quality of the NAND chips has been increasing since the iPhone 6.
    - jng 6y ago
      SD cards as present on Raspberry Pi, even the Pi 4, don't go beyond ~60MB/s. Older Pis get around ~20MB/s. It's the worst bottleneck of the system. Where do you get that 1 GB/s figure from?
      - vardump 6y ago
        Oh yes, another one of my pet peeves with Raspberry Pi: ancient slow SD implementation. https://en.m.wikipedia.org/wiki/SD_card https://en.m.wikipedia.org/wiki/SD_card SD Express can do up to 985 MB/s. SD UHS-II @300MB/s would be plenty for most SBCs.
  - zozbot234 6y ago
    > have to make assumptions about power being yanked at any moment I'm not sure you can make that "assumption" safely - plenty of SD cards have been bricked/trashed that way.
    - amenod 6y ago
      I think that was the GP's point.
- vardump 6y ago
  I wish more people understood this. People should demand higher quality SD cards (and slot controllers) instead of insisting on soldering equivalent chip on the board! Of course wouldn't say no to M.2 slot (or similar) either. :-)
  - simlevesque 6y ago
    You do know that the emmc on a Odroid is not soldered, right ? You can remove it easily with your hands.
    - vardump 6y ago
      I didn't know that. That's very nice!
      - simlevesque 6y ago
        Yeah, the read performance is like 10 times faster than a microsd on an rpi4. Also having your boot drive in eMMC is less of a risky because they are usually more reliable than microSD.
- zwieback 6y ago
  eMMC does have a wider bus and dual edge clocking so it's not a straight comparison. I think read might be fundamentally faster on eMMC but writing mostly depends on the NAND chips used inside.
  - mokus 6y ago
    UHS-I did add a dual-edge mode at 50MHz, but SD never got up to the 8 bits MMC supports (also at about 50 MHz, so UHS-I should be roughly half the speed of high-end MMC). UHS-II went to LVDS instead, which despite using fewer lanes can support much higher clock rates, so it’s not immediately obvious which is theoretically faster with newer versions. I need to get to work or I’d do the math. UHS-3 doubles the LVDS speed, and SD Express turned them into a PCIe lane. I haven’t kept up to see what MMC standards have been added lately, if any, but my impression is that it has been stagnant for a while.
gjsman-1000 6y ago
Eben Upton AMA at Pi 4 launch: Q: The SD-card speed increase is very welcome! Was an eMMC or M.2 slot considered? A: We don't think there's a compelling advantage to socketed eMMC over SD. M.2 would have been fun, but we didn't like the form factor considerations, and had no spare PCIe lanes. I think USB 3.0 SSDs are the way to go for high-performance storage. https://www.tomshardware.com/reviews/raspberry-pi-eben-upton-ama,6206-4.html https://www.tomshardware.com/reviews/raspberry-pi-eben-upton...

Having eMMC support is a game changer over a microSD card. It makes it feel like a real computer.

rjsw 6y ago

The ODROID-C2 has eMMC, doesn't feel as fast as the eMMC drive on another AArch64 machine that I have though.

mgulick 6y ago
Maybe, I don't have another eMMC board to test with, but compared to my RPi 3 with an SD card, the eMMC feels way faster. Very noticeable doing an apt upgrade. Note I use all of my boards headless.

zozbot234 6y ago

A microSD card is just MMC that's socketed instead of being soldered to the package/board. It's good for flexibility. With 4GB RAM, performance should be a non-issue either way.

myself248 6y ago
....over a narrow bus, and with controllers that have to make assumptions about power being yanked at any moment so they can't do proper SSD-like things that eMMC chips can do.
- vardump 6y ago
  Narrow bus? I think current SD card standards can go way past 1GB per second (note: see edit below). It's an implementation detail. In practice, these cheap boards will have a cheap eMMC soldered in that can't do these fancy things anyways. It's not going to be same quality chip like in flagship phones. Once that cheap eMMC fails, the device is bricked. Edit: SD card standards still can't go past 1 GB/s, max 985 MB/s. Either way, plenty for cheap SBCs.
  - zwieback 6y ago
    narrow as in bit width
    - vardump 6y ago
      So blame the bad narrow implementation?
      - zwieback 6y ago
        Not taking sides, just trying to clarify. I think there's a place for eMMC and SD but you're right chip quality and controller implementation is key.
  - zozbot234 6y ago
    I don't think even flagship phones have "quality chip" inside. Phone OS's are still running without swap memory support to cope with poor quality of their onboard eMMC (which leads to OOM-killing "background" apps instead of just swapping memory out.)
    - snalty 6y ago
      iPhones use NVMe storage and have done since the iPhone 6S and the quality of the NAND chips has been increasing since the iPhone 6.
  - jng 6y ago
    SD cards as present on Raspberry Pi, even the Pi 4, don't go beyond ~60MB/s. Older Pis get around ~20MB/s. It's the worst bottleneck of the system. Where do you get that 1 GB/s figure from?
    - vardump 6y ago
      Oh yes, another one of my pet peeves with Raspberry Pi: ancient slow SD implementation. https://en.m.wikipedia.org/wiki/SD_card https://en.m.wikipedia.org/wiki/SD_card SD Express can do up to 985 MB/s. SD UHS-II @300MB/s would be plenty for most SBCs.
- zozbot234 6y ago
  > have to make assumptions about power being yanked at any moment I'm not sure you can make that "assumption" safely - plenty of SD cards have been bricked/trashed that way.
  - amenod 6y ago
    I think that was the GP's point.
vardump 6y ago
I wish more people understood this. People should demand higher quality SD cards (and slot controllers) instead of insisting on soldering equivalent chip on the board! Of course wouldn't say no to M.2 slot (or similar) either. :-)
- simlevesque 6y ago
  You do know that the emmc on a Odroid is not soldered, right ? You can remove it easily with your hands.
  - vardump 6y ago
    I didn't know that. That's very nice!
    - simlevesque 6y ago
      Yeah, the read performance is like 10 times faster than a microsd on an rpi4. Also having your boot drive in eMMC is less of a risky because they are usually more reliable than microSD.
zwieback 6y ago
eMMC does have a wider bus and dual edge clocking so it's not a straight comparison. I think read might be fundamentally faster on eMMC but writing mostly depends on the NAND chips used inside.
- mokus 6y ago
  UHS-I did add a dual-edge mode at 50MHz, but SD never got up to the 8 bits MMC supports (also at about 50 MHz, so UHS-I should be roughly half the speed of high-end MMC). UHS-II went to LVDS instead, which despite using fewer lanes can support much higher clock rates, so it’s not immediately obvious which is theoretically faster with newer versions. I need to get to work or I’d do the math. UHS-3 doubles the LVDS speed, and SD Express turned them into a PCIe lane. I haven’t kept up to see what MMC standards have been added lately, if any, but my impression is that it has been stagnant for a while.

gjsman-1000 6y ago

Eben Upton AMA at Pi 4 launch: Q: The SD-card speed increase is very welcome! Was an eMMC or M.2 slot considered? A: We don't think there's a compelling advantage to socketed eMMC over SD. M.2 would have been fun, but we didn't like the form factor considerations, and had no spare PCIe lanes. I think USB 3.0 SSDs are the way to go for high-performance storage. https://www.tomshardware.com/reviews/raspberry-pi-eben-upton-ama,6206-4.html https://www.tomshardware.com/reviews/raspberry-pi-eben-upton...