Re: cheap 8-core ARM board

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Wed, Nov 23, 2016 at 09:11:51PM +0100, Reinoud Zandijk wrote:
> On Tue, Nov 22, 2016 at 02:52:03PM +0100, Christian Baer wrote:
> > with OpenWRT. The new and fast ones are all ARM based. That isn't
> > necessarily a bad thing but it noticeable. At the same time, the
> > Chinese are making laptops with MIPS CPUs.
> 
> Really laptops with MIPS CPUs? Haven't seen one come by yet but maybe I wasn't
> looking hard enough :)
> 
> My biggest problem with the ARM boards that are generally available is that
> the CPU is OK but the memory bandwidth is just not up to spec. Esp. with the
> PI1 and the PI2 (dont know about the PI3) the CPU can do a fair amount but
> don't try to crunch data with it since its 16 bit databus cripples the entire
> beast. Manipulating local data goes fast but as soon as you start processing
> larger things it just slows down tremendously. I should compare my PI board
> with both linux and NetBSD to see if it matters much; then we can exclude the
> pmap stuff.
> 
> My current NAS, a LG Marvell board has the same performance problem. Next to
> this the amount of `system time` it eats when streaming data to/from its SATA
> over the gb network port is appalling. Sometimes in the 30-50% and you get a
> few mb/sec max.
> 
> So yes, 8 cores might look fine but if they share a common 16 bit databus to
> DRAM, then thanks but no thanks. There are board like the NVidea (Tegra?)
> board that are exceptions on the rule but even then its max 32 bits wide
> AFAIR.

The Allwinner A20 has a 32bit DDR2/DDR3 databus, I would guess the H80
is at last 32bits too. 

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--