- Intro
- Picking the Right microSD Card
- MicroSD Card Speed Ratings
- Sequential vs Random
- Advice to Buyers
- Testing
- Using Stock SD Cards
- End
- Resources
Intro
It’s surprisingly easy to get a counterfeit microSD card these days. You may even have one and not know it. It’s a growing issue because counterfeit microSD cards aren’t as reliable. This means that over time, you’ll have ever increasing chances of data getting corrupted, which means the possiblity of losing your save files and/or games not running properly. If the operating system files get corrupted, then your handheld won’t boot properly as well.
Picking the Right microSD Card
For most retro systems, the speed of the microSD card will not increase performance noticeably. Most microSD cards these days are rated Speed Class 10, UHS Speed Class 1, or Video Speed Class 10 and this is more than enough for the purposes of emulation. Anything faster will not improve performance.
For capacity, 16GB to 64GB will be sufficient for non disc based systems such as the Game Boy Advance, and etc. For disc based systems like the PlayStation 1, you may want a higher capacity like 128GB if you want a large library of PS1 games.
For more modern games such as PS2, GameCube, PS3, X360, or PC games for handhelds like the Retroid Pocket 4 Pro, Odin 2, Legion Go, ROG Ally, and Steam Deck, getting a higher capacity and faster rated card may actually help. For handheld PCs such as the Legion Go, Ally, and Steam Deck however, it will actually be around the same cost to buy a larger capacity SSD and install it yourself.
Anectdotal evidence points to any legitimate Samsung and SanDisk microSD cards as being the most reliable. SanDisk is heavily counterfeited however so buyer beware.
You also do NOT need any high end or endurance card such as the Samsung Pro Endurance or SanDisk High Endurance. These are for security systems and dash cameras and will not benefit retro handhelds.
MicroSD Card Speed Ratings
For picking out microSD cards, you will mostly see these three different speed ratings, Speed Class, UHS Speed Class, and Video Speed Class. These speed ratings will be printed on the microSD cards themselves usually in the letter C, U, or next to a V along with either an A1 or an A2.
Speed Class (Speed in MB/sec in the letter C)
UHS Speed Class (Speed in 10MB/sec in the letter U)
Video Speed Class (Speed in MB/sec next to the letter V)
Application Performance Class
Sequential vs Random
Sequential read and write speeds are the ideal speeds and are way higher than random read or write speeds. Notice how they give you the random read and write speeds in IOPS if you refer back to the Application Performance Class chart.
Sequential reads/writes are like when files are copied over in bulk while random reads/writes are more akin to parts of files being updated by the operating system. The reason why sequential reads/writes are much faster is that even though flash memory no longer writes data next to each other like disc based hard drives, it still uses pages to access information. Sequential access uses significantly less pages than random access.
Advice to Buyers
Before we get into testing, we’ll now go over some of the best practices to avoid buying a counterfeit card in the first place. You can skip ahead to the testing section if this portion does not apply to you.
Brands
Samsung and SanDisk were the most reliable according to annecdotal evidence. However SanDisk is also highly countefeited, especially on Amazon.
Any 1TB card for under $20 is fake. Avoid brands such as Nuilask, Alisinsen, Krecoo, and etc. Some listings will have a few positive ratings because they sold legitimate 32GB or 64GB cards before switching the listing to the fake 1TB cards.
The Walmart Onn brand seems to be questionable as well in terms of reliability according to user reviews.
Best Buying Practices
Physical stores provide the best results. Stores like Best Buy, Walmart, and Target carry legitimate microSD card brands.
If buying online, avoid Aliexpress and Temu at all costs. Most of the microSD cards are either counterfeits, fake capacity, or have high failure rates. You may save money but you’ll pay for it later in dealing with data corruption.
The safest stores online are established photography and storage webstores such as B&H Photo Video, Adorama, Samsung, and etc.
Ebay and Amazon should also be avoided as well. If you have no choice but to buy from Ebay, only buy from established vendors like Adorama. Avoid any listings from sellers you don’t know.
For Amazon, avoid any listings that have third party sellers shipping from Amazon. Those listings have commingled or shared inventory. Even if you buy directly from Amazon, the inventory is shared by all the sellers so you can still get a counterfeit card.
When on an amazon listing, click on the link shown below to check other sellers on the same listing.
In this example, if we look at the image below, we see eTech and Direct Suppliers US are both shipping from Amazon’s own warehouses. That means the inventory is commingled and the chances of a countefeit card are high.
If we check the reviews, we can indeed see that people are getting counterfeit cards.
Testing
The first test is just a visual check. Compare your microSD card to an image from the manufacturer. Counterfiets usually have a very poor paint job and usually has misaligned text and/or spelling errors.
H2testW
H2testw will check if the capacity of your microSD card is real or not. It does this by writing data to the full capacity reported by the card and then reads the data back to make sure nothing is corrupted.
MicroSD cards that falsely report a higher capacity will oftentimes have a true capacity of 16GB or so. Once you go past that, the data will write over itself, causing corruption.
You can grab the utility here: https://h2testw.org/
If you don’t feel safe using third party software, run it in a virtual machine.
One you download and extract the file using a program like 7-Zip (https://www.7-zip.org/), you can select the English option to change the interface to English.
Before you start the test, I would suggest backing up your card with software like win32 disk imager for any handhelds that required you to flash the microSD card with programs like rufus or balenaEtcher. For operating systems like Onion OS or MinUI, you can simply copy the entire microSD card to another folder somewhere on your PC. If you don’t know how the microSD card was set up, create an image with win32 disk imager just to be safe.
Format the microSD card to emtpy it out so we can do the full capacity test.
Select the drive letter for your microSD card, and then select “all available space” and then press the “Write + Verify” button. This process will take some time, roughly thirty minutes or so for a 32GB card with slow write speeds.
If nothing fails, your capacity is legitimate. If your read or write speeds are much, much lower than advertised, than you may still have a counterfeit card.
Crystal Disk Mark
Crystal Disk Mark will test both sequential and random read/write access. It doesn’t need the microSD card to be formated. It just needs enough free space to perform the test.
You can download Crystal Disk Mark here: https://crystalmark.info/en/software/crystaldiskmark/
If you don’t feel safe using third party software, run it in a virtual machine.
I would recommend starting Crystal Disk Mark after connecting your microSD card to the PC. Once you do, after selecting the drive letter with your microSD card, you can simply press the “All” button at the top left corner to start the test. It will take a few minutes and give you the data as shown below. You can increase or decrease the number of tests and the size of the test using the top menu. You can use the right most option to change how the information is shown after the test is completed.
Samsung Card-UFD Authentication
The Samsung Card-UFD Authentication Utility will only work for Samsung branded cards and will only check to see if it is genuine or not. It will not do a capacity check or a read/write speed test. The benefit is that this test only takes a few seconds.
You can grab the utility here: https://download.semiconductor.samsung.com/resources/software-resources/SMCA_Win_P01_RC01_20230704.zip
If you don’t feel safe using third party software, run it in a virtual machine.
Once you start the program, you can plug in the microSD card and it’ll show this image if the product is a genuine Samsung product.
Using Stock SD Cards
Stock microSD cards WILL fail, it’s just a matter of when. However, if you don’t care about losing save data or having to reflash your microSD card when the operating system fails, then using the stock card will be an acceptable option.
If you can’t afford to buy a legitimate microSD card, simply make backups of whatever is important to you. Most of the time this will be your save files and save states. You can use utilities like Syncthing to sync your files using WiFi if it’s available on your device.
You can refer to Phyrex Tech’s guide on Syncthing for the Miyoo Mini Plus to get an idea of how to set it up: https://www.youtube.com/watch?v=UjVmqVoouYs
End
I hope this guide helped. If you guys have any questions or advice of your own, please feel free to leave a comment down below. As always, hope you guys are staying safe and sane out there, and catch you guys next time.
Resources
Some handy links for resources about microSD cards or utilities:
Software
►Garlic Press (Transfer files over usb for RG35XX)
https://github.com/prosthetichead/GarlicPress
►SyncThing (Sync saves over WiFi for MMP+)
https://github.com/XK9274/syncthing-app-miyoo
SD Card Classifications
►SD Speed Classification (sdcard.org)
https://www.sdcard.org/developers/sd-standard-overview/speed-class/
►Application Performance Specs (sdcard.org)
https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/
SD Card Info
►Why Sequential Write is Faster on Flash Memory (ycombinator.com)
https://news.ycombinator.com/item?id=12162665
►How Capacity is Faked (thomasrutter)
https://superuser.com/questions/1655339/sd-card-scam-is-it-possible-to-undo-and-hack-it-back-to-the-original-size
Ducky Obrien 