So, can you set an RPI4 to 32 bit for even more speed? My Pi4 config.txt (Debian Bookworm) says
# Switch the CPU from ARMv7 into ARMv8 (aarch64) mode arm_64bit=1 I haven't tried it because I don't know how the software will handle the timing. On Fri, Jan 12, 2024 at 1:37 PM gene heskett <ghesk...@shentel.net> wrote: > On 1/12/24 13:07, Alan Corey wrote: > > Are you forgetting that 64 bit is slower? In the arm world where it's > > easily switchable 64 bit is pokey when you don't need it. > > > Thank Alan, to put numbers behind that, linuxcnc has a thing called > latency-test on an rpi4b the armhf kernel I built from 4.19 srcs, can > respond to an irq in 12 microseconds, this in 2018. in 2023, an arm64 > rt-preempt kernel can only do that in around 50 microseconds. The huge > majority of that time is a increased size of the stack frame it has to > put away and then reload the environment to handle the interrupt. > > > On Fri, Jan 12, 2024, 12:54 PM <r...@neoquasar.org > > <mailto:r...@neoquasar.org>> wrote: > > > > > > > > Sent from my mobile device. > > > > > ------------------------------------------------------------------------ > > *From:* YunQiang Su <wzss...@gmail.com <mailto:wzss...@gmail.com>> > > *Sent:* Friday, January 12, 2024 10:11 > > *To:* r...@neoquasar.org <mailto:r...@neoquasar.org> > > *Cc:* noloa...@gmail.com <mailto:noloa...@gmail.com>; > > debian-ker...@lists.debian.org > > <mailto:debian-ker...@lists.debian.org>; debian-arm@lists.debian.org > > <mailto:debian-arm@lists.debian.org>; debian-de...@lists.debian.org > > <mailto:debian-de...@lists.debian.org>; > > debian-rele...@lists.debian.org <mailto: > debian-rele...@lists.debian.org> > > *Subject:* Re: Ability to further support 32bit architectures > > > > <r...@neoquasar.org <mailto:r...@neoquasar.org>> 于2024年1月12日周五 > > 23:59写道： > > > > > > Keeping in mind that I am new to this arena... > > > > > > I have some Intel systems - both 64-bit and 32-bit - that I might > > be able to use as build platforms. > > > > > > > I guess all of your hardwares are 64bit. You setup different OS on > them. > > > > No. I have multiple 32-bit systems, one of which is Intel. > > > > > What does the Debian team need from me to be able to use these > > systems? > > > > > > > It's not about performance of hardware. It is about some limitation > > of 32bit. > > 2 examples for it: > > 1. if we use 32bit value for time, it will overflow in 2038, then > > your time will be shown as 1900. > > https://en.wikipedia.org/wiki/Year_2038_problem > > <https://en.wikipedia.org/wiki/Year_2038_problem> > > 2. A single process (or maybe APP, not precisely), can only use > UP > > to 4GiB RAM. > > In fact on most system the value is less than 4GiB: > > on intel32, it is 3GiB > > on mips32, it is 2GiB > > But currently, it is not enough, for example, when we build a > > big APP, it will need much more RAM. > > The RAM does install in your Rack, but you can NOT use it. > > https://en.wikipedia.org/wiki/3_GB_barrier > > <https://en.wikipedia.org/wiki/3_GB_barrier> > > > > > I can't guarantee they'll be FAST, but I'll do what I can to make > > them EFFECTIVE. > > > > > > > If you are really need 32bit system. Maybe you can say out why you > > *REALLY* need it. > > For most users, the suggestion is: upgrade to 64bit. > > > > > > That's not at all what I was asking or talking about. > > > > --J > > > > Cheers, Gene Heskett. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > > -- ------------- Education is contagious.
