Choosing micro SD card for Raspberry Pi 4

So I have a new Pi 4 on hand, should I plug in an used 8GB micro SD card?


Well, I want to test the performance of the new pi, so let's not let the old SD card becomes the bottle neck!

Short answer:

At minimum, get a 16 GB card with A1 speed. 
I'd just add few more bulks to get a 32 GB with V30.

Been away from the card standards for a while, my last knowledge was class 10, U1, etc.

What is A1?  V10?  V30?

Simple enough, 'A' means Application, good for mobile phone to run application directly from, instead of old usage only storing data.

Now, if you guess 'V' for Video, you are correct!

V30 is good for 4K video recording without dropping frames.  That V30 has higher writing speed (~100MB/s) than A1 standard.

Some said for a pi 3, use at least an A1, which meets the the standard of certain IOPS, unit of random performance, the number of random access I/O operations in one second.  V30 preferred on Pi 4.

Raspberry Pi 4 needs heatsink or cool fan?

Raspberry Pi 4 CPU Temperature

Previously I have Raspbian Buster written to a SD card.  (see write Raspbian Buster to SD card on Linux)

Without GUI, only ssh into it, temperature was 46 degree Celsius.

    /opt/vc/bin/vcgencmd measure_temp
With GUI and browser opens 4 web sites at the same time, temperature was 60 degree.
(my indoor temperature is 22 degree)

According to some online info:
60 degree is the soft throttle
85 degree is the hard throttle

ref: https://www.raspberrypi.org/blog/thermal-testing-raspberry-pi-4/


My conclusion:
Working range from 40~80 is acceptable.
Normal web browsing one at a time, no worries.
(If temperature too high, pi will slow down CPU frequency to reduce heat automatically)
Any processing intensive operation, for example, building a library from source code, do get some cooling solution.