On 11/4/2011 11:02 AM, Lev Serebryakov wrote:
Hello, Arnaud.
You wrote 4 ноября 2011 г., 19:48:29:
$89, 700MHz Cortex A8, 256MB DRR2, micro-SD. However, do not expect
being able to run FreeBSD on it before a few years :)
What is so special about A8?
It is the consumer technology of today. The best people can afford
without being in ARM's R&D centers.
Let me tell you what is going to happen. ARM11 has been around for
years, it will take you a year or two to complete the project, nice,
hacker thrill, you did it. However, by the time you release it, the
Raspberry Pi will be sold-out and will be replaced by an ARMv7 core,
smaller, faster, eventually cheaper. By that time, the current
technology will be a 64bits MP-core ARMv8, And you will be in the
exact same situation as today, FreeBSD lagging one or two generation
behind Linux, keep up.
I am sure people will be running ARM9 (ARMv5) for a long time. Your
point that they will not be available as consumer products is well taken.
As I'm not a ARM specialist, I have several questions.
Does porting to ARM11 (ARVv6, am I right?) will make porting to
ARMv7 (Cortex) easier? You see, i486 adds some nice commands, tricks
and configuration registers to i386, but porting to i486 after you
have working port to i386/Protected mode is almost trivial.
Or it is completely different architectures, which doesn't have
anything in common?
ARMvX is only a core, as far as I understand. How much different are
implementations from different vendors? MMU? Bus? Configuration space?
We can run ARMv6/ARMv7using the ARMv5 model. But it would not be very
efficient. The ARMv6/7 new features can improve how things run. For
example we have hardware assisted atomic commands, we can remove all the
VIVT cache fixing code, and we can share the kernel address space in
each memory map.
But IMO, there are enough new features in the ARMv7 that finally make
something pv_entrys un-necessary.
The Cortex-A15 will be out next year with a whole new memory model. (40
bit physical, 32 bit virtual kernel, 40 bit hypervisor virtual). It will
have an AMBA change that can shed some bus mastering problems.
Besides the core new features, we always have all the different
peripherals for each SoC...
Why do you think, porting to different ARMs should go sequentially?
:) Yes, we (FreeBSD) doesn't have a lot of resources, but as nobody
could be forced to do what he don't want, it is better, IMHO, to have
ARM11 port, that to not have any ARM port at all.
But I agree, that port to Cortex-A8/A9 looks more interesting :)
The Cortex-A9 pandaboard is $174. The Cortex-A8 and A9 have some
differences, but they are more alike than the ARM11 and the Cortex-A8.
It will be tough to stay current with the hardware advances without some
kind of sponsorship.
--Mark Tinguely.
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