Everything druck said but cause they are cheap, I would get a fan case.
I've got several but like the one from Canakit the best when I don't
need access to the GPIO pins.  I haven't tried the big metal cases but
they look interesting.  You'll really like the performance increase over
the 3 when using a browser!

knute...

On 9/4/20 4:13 PM, druck wrote:
> On 04/09/2020 21:31, NY wrote:
>> I've got a Pi 3B+ and I'm thinking of upgrading to a 4B, partly to
>> free up the Pi 3 to do other tasks.
>>
>> I've got a couple of questions?
>>
>> - Can a "system disk" SD card (ie the same disk image) for 3B+ be used
>> for a 4B?
> As long as you've got the latest updates, you can just move the SD Card
> over.
>
>> Is it a case of "yes, but you won't be making full use of the 4's
>> 64-bit architecture and larger RAM"?  I'm being lazy and avoiding
>> installing and configuring everything all over again unless I have to ;-)
>
> I'd still stick with the Raspbian 32 bit userland until 64 bit OS's
> support everything such as GPU accelaration and GPIO libraries.
>
> You can run the normal 32 bit userland with the 64 bit kernel, by adding
> one line in config.txt You can then install raspbian-nspawn to run 64
> bit applications alongside 32 bit ones.
>
>> - I've read reports of the Pi 4 running quite hot and needing a
>> cooling fan, as opposed to just passive heatsinks, when used in a case.
>
> You don't need a fan, the large passive heatsink cases work well. I've
> got one Pi 4B with that, and one with a fan case. The latter runs
> cooler, but the former is well within spec idling at 45C and going up to
> 65C under load.
>
>> I'd be using it for recording TV (using external USB DVB decoders) to
>> a spinning disk (*) (not to the SD card), using TVHeadend, for
>> SMB-sharing folders which are accessed by Windows PCs, and maybe also
>> for running simple software such as a browser or an email client. On
>> my 3B, the CPU usage is barely measurable for recording from three
>> different sources simultaneously, while serving one of the video files
>> to a Windows client,
>
> That shouldn't change.
>
>> but it shoots up to nearly 100% as soon as I run Firefox or Chromium,
>> even when a static page has been loaded. Is it a known problem with
>> the Pi 3 (maybe fixed on the Pi 4) that browsers tend to hog the CPU?
>
> You'll see a massive difference using web browsers thanks to the extra
> memory and processor speed. Browsers that use separate tasks for each
> tab can make use of all that extra memory even though they are 32 bit.
>
> ---druck

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