60-80% of the read speeds I'm guessing. Maybe 30-35MBps on the lower conservative end. Funny they don't mention it though since the write speed is what really limits how fast you can take pictures or record video as you wait for your device to empty it's buffer.
[citation][nom]goodguy713[/nom]why put something like that on usb 3.o ? usb 2.o is good enough .. marketing i suppose.[/citation]
USB2 is limited to around 30MB/s realistic so it would be a bottleneck in some situations.
Yes they never seem to post write speeds in these ads thinly disguised as articles! It is almost if no one ever needs to write to these devices, they are magical devices just read from them and get the exact information you are looking for!
[citation][nom]face-plants[/nom]60-80% of the read speeds I'm guessing. Maybe 30-35MBps on the lower conservative end. Funny they don't mention it though since the write speed is what really limits how fast you can take pictures or record video as you wait for your device to empty it's buffer.[/citation]Based on what? Low speed cards? There's no way to know until they release more specs, however existing high-speed microSDHC/XC cards tend to have lower write speeds as a percentage of their read speeds.
For high-speed cards, I've seen a bunch of SDHC/SDXC UHS memory cards with read speeds of 30-40MB/sec. For those same cards, I've seen write speeds as low as 25% of the read speed. Most are in the 33-45% range.
My guess of write speeds of 60-80% of the read speed was based on previous experience.
I obsessively run HDTune and h2bench on every flash drive, sd card, ssd and hard drive that comes into my shop. I have read and write test results for over 300 diffrent devices and nearly 100 just from MicroSD and SD cards.
Having said that, most of the memory cards I test are customer equipment, meaning they're usually the cheapest available cards since they don't care or know about the varying performance differences between higher end SD cards.
I was going to argue with your claim about how much slower write speeds are on the newest sd memory but after doing some research, you're right. In fact, higher performance NAND-flash memory has write speeds less than 20% of the stated read speeds.
In a technology overview directly from Toshiba, they compare different types of NAND flash memory and NOR memory. In general:
SLC NAND Chips have read rates about 3x their write speeds
MLC NAND Chips have read rates 7-9x faster than write speeds (and support much higher capacities)
MLC NOR Chips can read at rates of 150-200x faster than their write speeds. The read speeds aren't amazingly fast, their write speeds just suck terribly. This is why NOR-flash is rarely used for storage applications but works well for booting from flash or executing code directly from the flash memory. Think of your cell phone booting etc.