On Wed, Feb 2, 2011 at 10:02 AM, Gordan Bobic <gordan(a)bobich.net> wrote:
Luke Kenneth Casson Leighton wrote:
>> Unfortunately, I'm not a hardware hacker. But, as a consumer, I'd say
that a "1gb NAND Flash" is quite a bit below the level. I also wouldn't care
much about a 1280x720 screen if the hardware wouldn't be capable of playing the video
flawlessly. Or, if there was an HDMI port to connect to TV, which is, in my taste, better
suited for watching.
> yep - all the designs i've worked on, and all the CPUs found (so far)
> were selected precisely because of the HDMI output capability. i'd
> kinda ruled out the spea1310 because you need an extra IC converting
> LCD to DVI/HDMI or even *shudder* a PCI-e graphics IC (volari Z11 god
> help us is about the only free-software-compatible option)
I was just thinking about that, actually. If you're making a custom
mobo, then as long as you can find an ARM SoC tht has PCI-e, you could
just apply an MXM module and plug in an ATI or Nvidia GPU for which we
already have passably working OSS drivers.
Of course, this defeats the purpose of the exercise - who in their right
mind would use a 2W CPU with a 30W+ GPU in a laptop?
Not to mention cost. Unless it is in significant (>100,000 unit)
quantities, MXM modules are $100 a pop. Even then, it is not a great
Who in their right mind would pair an $18 SoC with a $100 GPU? It is
design insanity to quadruple the BOM like this.
> gordon is right about the SD/MMC card thing, but the "level
> can at least guarantee above 10mbytes/sec *read* capability. so
> _yes_ to the SATA interface.
The 10MB/s is _supposed_ to be for worst-case sequential writes. There
is, however, no defined benchmark
(there is, but you need to be a paid up member of the SD Association to get it)
I'm glad we agree on anything other than SATA being unworkable.
I will also point out that a SATA NAND controller that is capable of
more than 20MB/s is going to cost you about $2.50 per gigabyte,
minimum $35. 2.5" SATA SSDs disks are also rather large for the
purpose. Sandisk make some nice MicroSATA SSDs as do, now, Toshiba if
you have a December 2010 MacBook Air, but they are either not as fast
as you want (20-30MB/s), or more expensive than the rest of the board
put together. There is a very good reason Apple's hardware costs so
much money and it is absolutely not price gouging.
(side note: We designed a developer system for IBM once; a quad core
G5 workstation, an open source, open design alternative to the Mac
cheesegrater. When it turned out the board alone would cost more than
buying a Mac G5 we handed them the schematics and the spec and
abandoned the project. Nobody wants a $1500 motherboard with a $1500
CPU set, and being told to buy your own hard disks, when you can go to
Apple and buy it prebuilt with cooling and graphics card and an
operating system for the same price.)
If you want cheap, plentiful and fast NAND on the board, you would be
better off using the internal flash controllers and soldering the
chips to the board. However you are limited by size and of course the
performance is not as you would expect (NAND disk does not necessarily
equate to 215MB/s Intel X series performance. Intel have a very
specific configuration to get that speed. Embedded NAND controllers
won't do it. Embedded SATA controllers won't even get the full
performance of the Intel devices).
This is exactly where you will get if you're trying to massage the
Tegra2, MX53, OMAP4 into a high end laptop; it will not meet your
expectations. They are not designed for those environments. Tegra and
OMAP4 are phone/tablet chips almost entirely focused on Android. MX53
is for in-flight entertainment, Ford Sync, handheld media tablets,
that kind of thing. Remember when you think about speeds on devices,
they are always listed as maximums. Yes, SATA-II is 3Gbit/s (actually
about 2.4Gbit after you get past the 10-8 encoding) but does a device
need to run at that? Not at all. USB 480Mbit/s? Nope.
You can't design a system, keep it cheap and make it a volume seller
by just picking the chips with the biggest numbers.
Matt Sealey <matt(a)genesi-usa.com>
Product Development Analyst, Genesi USA, Inc.