sdspeed h2testw for macOS SD card test testing OS X verify integrity flash card fraud: sdspeed

sdspeed

Software to verify the integrity of a flash SD card or USB device

You can test SD (secure digital) cards but also USB flash drives, even hard drives that are connected through USB.

Are you looking for SD card speed test on a Mac, how to check speed of memory card, SD card speed test,
flash card read write test, how to check SD card speed or software to measure micro SD performance?
Is your SD Flash Memory Card or USB Flash Drive fake?
SD Card Speed Test, H2testw for Mac), Pen Drive, USB Flash Drive, SD card benchmark

Download via PayPal below, first like it 😉

Features

Note: Use at your own risk. Make always a full backup first of your OS X system and your external cards you are testing.

  • Allows you to disable Spotlight searching for devices. This does improve performance on your SD card or USB memory devices
  • Does support USB flash drives as well as external USB hard disks
  • Full report for your documentation

Hello, just take a little poll, just 1 (one) question:

[yop_poll id="1"]

 

This little tool sdspeed let's you speed test your USB and SD Flash Drives Cards. There are many Flash Frauds and a need to fight them. This utility can check SD Flash Cards, USB Flash Drive, Pen Drive, Memory Stick. It does an extensive write and read test. So every single bit will be tested if it can be written and afterwards read back. It does this by test for Counterfeit or Fake USB flash drives, and check your USB Flash Drive for errors. It works basically with any USB memory device like USB harddisks.

Fake flashdata corruption from flash memory chips, class speed under performing, fake memory card, fake memory chips altered to lie about their true size (Hacked Memory). The black market is strong. More then 1,000,000 flash memory chips are "upgraded" and manipulated every month and many brand name manufacturers such as: SanDisk, Transcend, Sony, ADATA, Kingston Technologies, Lexar and RITEK have been impacted.

sdspeed is the only product that measure the read and write rate of your SD memory card you can trust based on open-source software
(Deutsch:) sdspeed ist das einzige Produkt das Hersteller unabhängig die Lese- und Schreib Rate Ihrer SD Speicherkarte misst, basiert auf open-source software

Need for Speed

The SD Association 1 defines standard speed classes indicating minimum performance to record video. Both read and write speeds must exceed the specified value. The specification defines these classes in terms of performance curves that translate into the following minimum read-write performance levels on an empty card and suitability for different applications (Source: Wikipedia):

ClassMinimum performanceApplication
Class 22 MB/sSD video recording
Class 43 MB/sHigh-definition video (HD) recording including Full HD (from 720p to 1080p/1080i)
Class 64 MB/s-- "" -- (same as above)
Class 105 MB/sFull HD (1080p) video recording and consecutive recording of HD stills (high-speed data bus)
UHS Speed Class 1 (U1)10 MB/sReal-time broadcasts and large HD video files (UHS bus)
UHS Speed Class 3 (U3)30 MB/s4K video files (UHS bus)

 

How to spot a fake product

So you bought an USB Flash Drive of tremendous gigantic capacity (up to 2 terra bytes) and you are not sure if it can store really such a huge amount of memory?

There are many different variants.

Category: Empty parts

This is funny! There are products which are just empty.

Symptoms

  • The device looks perfect. But it's only the housing
  • The device is in fact empty. There is no electronics chip inside or whatsoever. Just a peace of plastic
Empty device: Just a bit plastic and metal. Nothing else. Storage capacity is 0 (zero) bytes

Category: Broken parts or Drive's Showing the Wrong Capacity

512 GB size but can read only 8 GB back

Well, the product does look perfect - and it is maybe, probably. BUT it's maybe a broken or rejected device, which then was dropped out from the factory which does indeed produce real storage products. But as usual, not any product makes it to the customer. Why? Because they fail to pass the final quality control test. These are failed, broken devices.

Symptoms

  • The device does in fact report 64 GB free space on your system but it can not read back such an amount of space
  • The device will show for example 64 GB free space but in reality it can store (read) only 7 to 8 GB
  • The device can store maybe 64 GB, but you will not be able to read back all data later on
  • Often there is a label glued on it which says 64 GB or whatever.

It's not clear if these are just broken parts or if it's possible to use special software to make the device report much more space then it really has.

fake size - shows 64 GB but write and readable are only about 8 GB

See what's inside.

 

FAQ

Q: How to disable Spotlight manually?

You can exclude a specific folder from the Spotlight index from System Preferences, by adding .noindex to the end of its name, or by creating an empty file named .metadata_never_index inside it.

  • adding .noindex to the end of the folder's name, or
  • creating an empty file .metadata_never_index inside the folder (eg with touch yourfolder/.metadata_never_index)

Q: How to reenable Spotlight indexing on an SD Card?

A:

Spotlight: How to re-index folders or volumes

Learn how to re-index a folder or an entire volume for Spotlight.

  1. From the Apple () menu, choose System Preferences.
  2. Click Spotlight.
  3. Click the Privacy tab.
  4. Drag a folder or an entire volume (your hard drive) to the list.
  5. If prompted for confirmation, click OK.
  6. Remove the item or volume you just added to the list by clicking it and then clicking the minus ("-") button.
  7. Close Spotlight preferences.

Spotlight will re-index the contents of the folder or volume.

Source: https://support.apple.com/en-us/HT201716

Q: I can't write on my SD card, it's read only even if you put the switch to unlock position.

A: Finder says "you can only read" or so. Maybe the switch on the SD card is not good and/or does not held in place. Maybe fixating with a thin tape can help. Other reported it worked for them to put the micro switch in a middle position. I don't think this will help but you never now. Just try it.

 

Q: Can a SD Card get broken by ESD, Electrostatic Discharge (Educational Video from Apple)?

A: Yes. So make sure you are discharged before handling with memory like SD Cards, USB Sticks, etc.

Any none conductive materials like plastic can be electrically charged. For example a simple foil, synthetics fabrics, walking on the floor, etc.

So it's best not to touch any device if you are charged to handle it safely.

More over, it can be working but fail later on the field.

For more information see teaching Video from Apple about ESD:

Q: My SD Card / USB Stick does not get recognized any more. What can I do?

A: First, clean the blank connection pins with pure alcohol. I had an USB-Connector on an SONY MICRO FAULT TINY 1GB Stick which was not recognized at all. I just cleaned the blank pins a bit and it works fine now.

Q: How can I create a huge file with random numbers in it?

A: Just use this command in a Terminal

Enter the command without the leading $ sign. This is just your prompt.

Why 1048576? This is just 1024 * 1024 which is 1 mega byte. And 1024 megabytes are 1 giga byte.

$ dd if=/dev/random of=file.txt bs=1048576 count=1024
$ ls -lh file.txt 
-rw-r--r--  1 myself  staff   1.0G Oct  2 12:50 file.txt
$

 

Q: My SD Card does not format! Please help!

(You can not format your SD Card. Can't format SDHC card.)

A: Try SD Formatter from the sdcard.org Association itself.

Download SD Formatter 4.0 for SD/SDHC/SDXC

https://www.sdcard.org/downloads/formatter_4/index.html

This software formats all SD memory cards, SDHC memory cards and SDXC memory cards. SD Formatter provides quick and easy access to the full capabilities of your SD, SDHC and SDXC memory cards.

The SD Formatter was created specifically for memory cards using the SD/SDHC/SDXC standards. It is strongly recommended to use the SD Formatter instead of formatting utilities provided with operating systems that format various types of storage media. Using generic formatting utilities may result in less than optimal performance for your memory cards.

The SD/SDHC/SDXC memory cards have a "Protected Area" on the card for the SD standard's security function. The SD Formatter does not format the "Protected Area". Please use appropriate application software or SD-compatible device that provides SD security function to format the "Protected Area" in the memory card.

Q: How to speed up your Pen Drive up to 30% on Windows

A: Format with NTFS

This will speed up data transfer by up to 30%. Also format your pen drive with NTFS, as FAT32 has restrictions.

1. Right click the pen drive properties from my computer

2. Under the hardware tab you will find your pen drive. Highlight and click properties.

3. Under "polices" change the option from "optimize for quick removal" to "optimize for quick performance"

4. Done!

More

About the SD and SDXC card slot (Apple HT Page)

"Some Mac computers feature an SD (Secure Digital) or SDXC (SD extended capacity) card slot that enables these computers to read and write data to SD media inserted in the slot. Learn more about the SD and SDXC card slot." For more information visit: https://support.apple.com/en-au/HT204384

 

Support

Just leave a message below.

View Comments

  • I have just tested the sdspeed app on a 16GB Class 4 SDHC card and found that it takes about 30 seconds or so to speed up to the actual WRITE speed of the card and the results then stabilise, giving an accurate reading of 4.8MBps.

    However, at that point it is only about !% through testing the Write speed and I want to test the READ speed.

    It looks as though I would have to wait a very long time before the READ test begins.

    Is there any way to switch to the READ test quickly?

    • Hmm… I think it’s because the test application does first write data then read it. So you have to wait after it has written the whole space on your SD card for a serious read test of *all* your “sectors” on your SD card.

    • It's true that you have to wait for a long time if your SD card is slow and/or has much space to offer.
      BUT: After all you can be sure that it has tested the whole SD card memory space. If you can read and write the first few mega bytes does not mean that you can read and write the whole SD card space.
      With this test, you can be sure about it.

      • Other tests read and write only the same file over and over again which is surely faster but does - in my opinion - not measure the true put through speed of read and write cycles over the whole space available on a SD card.
        Also if other tests read and write the same file over and over again: They can fool the testing by internal caching mechanisms.

    • Hmm... start it from command line (terminal) with
      $ ./sdspeed.app/Contents/MacOS/sdspeed
      and see if it prints out some errors. Do also a
      $ file ./sdspeed.app/Contents/MacOS/sdspeed
      which should give you:
      ./sdspeed.app/Contents/MacOS/sdspeed: Mach-O 64-bit x86_64 executable
      ---------
      I think I found it. It happens when you did insert a Card, then after the run has been completed, just removed it (by hand, not unmounting it)... the Start button remains clickable.. if you then hit Start, the app will quit.
      You can force to redo the status by just clicking on the sdspeed icon within the window on top lef, the black logo of a symbolic SD card.

      • Hey...thanks for your reply.
        I have not been able to even do a first run.
        I tried clicking the sdspeed icon on top left and tried again but nothing.

        I am not very good at terminal and do not understand what you mean when you put $ . or $ file . so the tests on terminal come out as -bash: $: command not found

        • Hello HL

          Let me explain what I mean so you can understand:

          Terminal: It's just a so called Shell, like DOS-BOX etc. where you can type in commands, list and view and execute applications, etc.
          So if you open Terminal, the "black hole" window will appear. There the so called Prompt starts always with a dollar sign ($).
          (What someone would type in within the Terminal is in bold here.)
          So if I write please type in:
          $ ls
          that means that you type in "ls" within the Terminal application to execute the command ls which stands for listen files within the current folder.
          Just try it!
          Let me know if you succeed.

          Type in also uname -a like so:
          $ uname -a
          (without the leading dollar sign)
          which gives you your precise machine name and system you use. Example, if I type in this command my Terminal looks like this:
          -------------------
          $ uname -a
          Darwin michael 12.5.0 Darwin Kernel Version 12.5.0: Sun Sep 29 13:33:47 PDT 2013; root:xnu-2050.48.12~1/RELEASE_X86_64 x86_64
          $
          --------------------

          The same you can do to start sdspeed right from within your Terminal like so:
          (Your screen will be then something like this)
          ------------------
          $ /Applications/sdspeed.app/Contents/MacOS/sdspeed
          ------------------
          (Remember without the dollar sign)
          Then let me know what the output (your screen) shows up... maybe it gives us a clue what's going on.

          Best regards, Michael
          BTW: There are good video tutorials out there on youtube, etc.

  • Thanks for explaining Michael.

    Once i typed the command without the $ sign this is what showed up.
    First it opened up the app and this appeared:

    Andress-MacBook-Pro:~ hardline$ /Applications/sdspeed.app/Contents/MacOS/sdspeed2013-10-23 11:54:14.424 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:14.425 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:14.426 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:14.426 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:14.427 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:14.427 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:14.427 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:16.424 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:16.425 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:16.425 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:16.426 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:16.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:16.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:16.427 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:18.424 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:18.425 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:18.425 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:18.426 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:18.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:18.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:18.427 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:20.424 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:20.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:20.425 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:20.425 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:20.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:20.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:20.426 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:22.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:22.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:22.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:22.425 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:22.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:22.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:22.426 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:24.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:24.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:24.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:24.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:24.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:24.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:24.426 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:26.424 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:26.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:26.425 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:26.425 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:26.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:26.426 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:26.426 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:28.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:28.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:28.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:28.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:28.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:28.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:28.426 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:30.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:30.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:30.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:30.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:30.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:30.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:30.425 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:32.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:32.423 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:32.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:32.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:32.424 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:32.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:32.425 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:34.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:34.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:34.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:34.425 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:34.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:34.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:34.426 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:36.422 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:36.423 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:36.423 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:36.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:36.424 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:36.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:36.425 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:38.423 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:38.424 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:38.424 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:38.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:38.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:38.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:38.425 sdspeed[9716:707] - Read only = 0
    2013-10-23 11:54:40.422 sdspeed[9716:707] DEBUG:
    2013-10-23 11:54:40.423 sdspeed[9716:707] - Name = HARDLINE
    2013-10-23 11:54:40.423 sdspeed[9716:707] - Name (local) = HARDLINE
    2013-10-23 11:54:40.424 sdspeed[9716:707] - Capacity = 14.9 (GB)
    2013-10-23 11:54:40.424 sdspeed[9716:707] - Capacity = 16013066240 (Bytes)
    2013-10-23 11:54:40.425 sdspeed[9716:707] - Capacity = 16013066240 (Bytes UI)
    2013-10-23 11:54:40.425 sdspeed[9716:707] - Read only = 0
    2

    over and over again ...it wouldnt stop.

    Then once i hit the start button, the application quits and this appeared on the terminal:

    Creating file 1.fff ... sdspeed: Can't create file /Volumes/HARDLINE/1.fff: Permission denied

    • Creating file 1.fff … sdspeed: Can’t create file /Volumes/HARDLINE/1.fff: Permission denied
      -------
      Check if you can write a file on you card. Check also under which user account sdspeed runs. Just go to applications folder click or select sdspeed. Then hit cmd+i for information. In the bottom you can see under which username and group sdspeed will be executed. Show me a screenshot and change it to your username and group.

  • Hi Michale,
    Firstly, thank you for the software as I've had rather questionable SD cards in the past but had no real way of testing!
    I ran sdspeed and it ran the Write test fine but stayed on 100% and would not run the Read test! One thing I noticed was that the button had changed to "Please wait Start Speed test" and was still greyed out. I left it like this for 5 minutes and nothing happened so I quit the app. My spec's are:

    Model Name: Mac Pro
    Model Identifier: MacPro3,1
    Processor Name: Quad-Core Intel Xeon
    Processor Speed: 2.8 GHz
    Number of Processors: 2
    Total Number of Cores: 8
    Memory: 14 GB
    Mac OS: 10.9 Mavericks

  • Does the choice of card reader affect the results? If so, any recommendation on a reader that gives best (ie. most accurate) results?

    • Hello David. The card reader does in fact affect the results. Some users reported this. I do not have a special card reader, but basically I think it's best to use the built in card reader on your mac. (Basically as less wires in between your card and your computer.) If you test your card on USB make sure you use the *nearest* one to your computer (builtin) not external USB adapters for best results. Hope that helps.

      • Thanks, Michael. Yes, I found that the results were different whether I use the built-in SD reader or an external USB one. Thanks for the explanation.

  • I have a SanDisk Extreme Plus 32GB SDHC (Read: 80MB/s, Write: 60MB/s). When I use sdspeed 1.0.1, it shows Read: 49MB/s, Write: 46MB/s. However, when I use AJA System Test, it shows Read:82MB/s, Write: 46MB/s. AJA System Test is showing the correct read speed. Is this a limitation of sdspeed?

    AJA System Test - http://www.aja.com/en/software

    • 1) Just try "Version 1.1 (BETA)", and disable and remove Spotlight for your SD-Card. Spotlight starts automatically for some SD-Cards if you plug in an SD-Card which slows down measurements.
      Let me know how the results reads after disabling and remove Spotlight on your SD-Card.
      2) Depending on how the testing is done, it can be that the results may vary. (Note that sdspeed tests your whole SD-Card, bit for bit just to make sure that any bit on your SD cards works just fine. So it fills up the SD card first and then reads it back and check if the pattern written is equal with the pattern read.)

  • I just found this little gem, and was reading through the comments section.

    Michael, I just wanted to say thank you for being so awesome and patient in explaining in detail what needs to be done! You sir, are a great person!

    Thank you for being you ;)

    Warm regards,
    Isa

  • I tried this with a SanDisk Extreme 128GB on Macbook Pro mid-2010 (7,1). The card should read and write at 45MB/s according to the spec.

    Write test took several hours, and came up with about 14MB/s. Based on what I read on the internet, that's a limitation of built-in card reader.

    It now says "Do read test please wait", but no read test is happening. Instead, the whole computer has gone very slow and the processor fan is running fast. I left it for several hours and still it is the same. Looking in Activity Monitor, sdspeed seems to use only around 2% of CPU and very little memory. It has got up to 8 threads now though. To get the computer back to normal, I had to do a full reboot - closing sdspeed alone didn't help. So sdspeed has somehow really messed up the OS! Oh dear!!

    In any case it seems like for some reason sdspeed doesn't work with my computer or with this card.

    • Thank you for your report. It's difficult to say what the problem could be from a distance. Is this device you have tested ("SanDisk Extreme 128GB") an external harddrive? 128GB is a huge amount of data. If you test external harddrives (basically any device with movable parts in it) with such a huge amount of data can get very very hot... be sure you cool down it if needed during the test with good air-flow around the device. This is all I can say at the moment. sdspeed does check any data on a disk. Best use is for a little amount of data. Maybe in future version there needs to be an option where you can setup the amount of data which should be tested, to limit it to about 2 GB or whatever.