[Arm-netbook] 9nov11: progress on allwinner A10

[Luke Kenneth Casson Leighton]

On Wed, Nov 9, 2011 at 9:00 PM, Gordan Bobic <gordan at bobich.net> wrote:
> On 09/11/2011 20:44, Luke Kenneth Casson Leighton wrote:
>>
>> ok, just a quick thoughts / status update.
>>
>> we've had it confirmed that the CPU is external 2gb addressing but
>> *internal* limited to 1gb (!)
>>
>> little factory is still going over the BOM, but want to put in 512mb
>> DDR RAM ICs because they're cheaper.
>
> That's a shame. IMO the biggest shortcomming of available devices is small
> RAM. I can just about live with 1GB, 2GB would be nice. Especially since the
> development version of OLPC is available with 3GB (Marvell).
>
>> they were planning to make room for up to 4gb NAND flash *but*...
>> something just occurred to me / my associates: thailand's under water.
>>
>> the implications of that are that the factories which used to make
>> low-end IDE drives and pretty much every SATA drive under 80gb no
>> longer exist... and probably won't ever be rebuilt.  everyone's moving
>> to SSDs for low-end, and the prices for larger HDDs are rapidly
>> escalating.
>>
>> now, for free software developers we don't give a rat's arse: there's
>> always room to cut down to emdebian, or use cramfs, or... whatever:
>> there's always creative ways to make a bit more room, but i've been
>> connecting the dots a bit from various peoples' input, talked it over
>> with my associates and we came up with an idea.
>
> I'm not sure what the point is of having internal flash if you have a SD/uSD
> slot AND a SATA port. Dropping internal NAND alltogether seems like an
> obvious choice.

 it is... until you work out the speed (he said... not having actually
done it yet!)  SD3.0 UHSv1 (whatever it is) qty 1 is _only_ 4 bits
wide, and maxes out at... well, you can check the wikipedia page, off
top of head i think 150mbits/sec is about the lot.

 by contrast, the NAND flash interface is ... *checks*...8, 16 or
32-bit wide, and you _can_ do "non-conflict" simultaneous 8 bands of
DMA which matches with the 8 NAND select lines, obviously, so someone
has thought about this :)  that NAND flash, i seem to remember,
somewhere, it supports up to 2ns NAND, so frickin 'ell that's 500mhz
max, i don't dare look up the prices on those, but 8 of them all doing
concurrent non-conflicting DMA transfers, i believe the point is made?
:)  probably horrifically expensive, too.

>> alain (williams) asked a very pertinent question, he said, "ok yep
>> count me in, but how do i make any money from this?" and it put me on
>> the spot and i went, "um, well... how about you do servers but use
>> these as low-power ones" and then i realised of course, he's a CentOS
>> maintainer, hosts some packages, so he's going to try CentOS for ARM
>> and then well if that works, he'll be the maintainer of the ARM port
>> of CentOS servers.
>
> I may have beaten him to it. I have a beta spin of RHEL6 port for ARM
> running right now with all relevant packages patched as required and built.
> :)

 yaay!  well then that's gloody grilliant, it means CentOS is a breeze.  yaay!

> If anybody is interested in it, drop me a line and I'll notify you when it
> is downloadable (probably about a week, two at the most).
>
>> then we put two and two together and went, "hang on, these are
>> effectively blades, why not have a chassis like the ZT-Systems one,
>> with a gigabit backbone, space for SATA drives, and up to 8
>> EOMA-PCMCIA-compliant CPU cards, each with 1gb DDR3 RAM and these
>> Cortex A8s?" it'll all be low-cost, you can get 40gb to 80gb SATA
>> drives, turn it into a big software RAID or NAS box or a
>> high-performance (but higher-than-average latency of course)
>> load-balanced server aka cloud jobbie.
>
> I like this idea - A LOT. I'd certainly be interested in buying some.
>
>> at which point i went "oh shit - low-end SATA drives don't bloody
>> *exist* any more!" :)  [look on ebuyer's site for SATA drives below
>> £50 - there aren't any].
>
> Well, on something this low power you'd want SSDs anyway.

 yeah, precisely.  the question is: would a bunch of NAND ICs beat the
price or performance of off-the-shelf SSDs with SATA-II interfaces,
and if so, how the heck do i justify it to the factory?

 btw they're set up - psychologically - for "tablets, netbooks, STBs",
their heads would melt if i made any mention of "servers".  so i
believe it would be sensible to get the motherboard made elsewhere /
somehow-else: a large 2-layer board probably would do the trick, even
using KiCAD, hell there's got to be someone around with the expertise
to lay out some tracks to an 8-port Gigabit Ethernet IC, bung on some
SATA interfaces x8 direct to connectors, connect some I2Csx8 to an
EEPROMx8, it's a cut-paste job!

>> and people could do their own wear-levelling (i hope!), i remember how
>> everyone keeps bitching about how these bloody SSDs always get in the
>> way with the stupid, stupid assumption that there's going to be a FAT
>> or NTFS partition on it.
>
> Hmm... Doing your own wear leveling? How quaint...

 a keyyboarrrdh? how quaint... :)  sorry, my embedded experience dates
back to the ETRAX 100mhz, the guys who did jffs i think it was...
achh, too long ago to remember.

> I think the server idea is _great_, provided it has at least 1GB of RAM per
> board, a SATA port and at least 100Mb networking.

 yep that's easily doable.  made a note.

> Sign me up for some of those for sure.

 fantastic.

> OTOH, I am not sure I see the point of having on-board raw
> NAND instead of a uSD slot. Yes, even the fastest SD cards are painfully
> slow when it comes to write IOPS, but arguably raw NAND won't be all that
> much better for any serious workload.

 ... Chip-selects with independent concurrent DMA x8 @ 500mhz, 32-bit?
:)  don't ask me how much those are, i don't know - anyone got a
handle on the prices and capabilities of NAND ICs?

l.