I discovered that some initial lots of the Raspberry Pi 4 may have a sort of hw/sw bug that may be related to USB 3, and maybe also to thermal management and throttling. I would like to understand these issues before buying a Raspberry Pi 4.
If the problem a hardware issue, how can I determine if the RPi4 unit I purchase is the "fixed version"?
If the problem is a software problem, where do I find a documented procedure to correct the problem?
Yes - the RPi 4 has had some "controversies" (il dibattito?). One is related to a flawed USB-C interface design. The other is not a design flaw, but rather a thermal management issue. Here is a summary, as I understand these controversies.
The Raspberry Pi hardware design team made a significant design error in the design of the USB-C (not USB 3) interface. This is a hardware issue, and has nothing to do with software. Other questions have been asked here re this USB-C design flaw, and you can get further details by searching, finding and reading them - for example
Note that this hardware issue/design flaw will have no impact if you always use the "official" power supply. Likewise, if you use a NON e-marked USB-C cable, you will have no problems powering a flawed RPi 4 unit from any compliant USB-C power source. Here's a verified list of NON e-marked USB-C cables.
Until you have the hardware in your hands, the only way to tell that you're getting the "fixed version" is to ask the vendor. Once you have your unit in hand, you can verify that it's the fixed version by running this command from the command line:
$ cat /proc/cpuinfo | grep Revision
If the result is Revision : a03111 (or b03111, or c03111), it's an ORIGINAL RPi4, and built with the USB-C design flaw. The "fixed version" currently reports Revision : a|b|c03112, but note to future readers - this Rev number may change if there is another hardware update. Also note that the a|b|c prefix only refers to the memory configuration REF.
In accordance with the laws of physics, the increased performance of the RPi 4 created higher CPU/GPU component temperatures. Component temperature in RPi 4 is largely managed by throttling: the clock speed is reduced automatically to limit the component temperature increase. This is not a "bug", and it is not a design error - it is simply a technique for keeping component temperatures within safe limits.
The "throttling" technique is implemented in firmware. The Raspberry Pi design team has released several updates to this firmware which have improved the tradeoff between performance and thermal management.
The firmware is automatically updated as part of the apt upgrade process. If you want to exercise control over which version of the firmware you run on your unit, there is some documentation explaining how to install the firmware in EEPROM.
Non ti preoccupare. The Raspberry Pi 4 is not perfect, but what is? And you'll find that the support community here is very good.