[Arm-netbook] github.com/slapin/a13board , was: expeyes-SBC, minimalist A10 board

[Ajith Kumar]

> Hi, people! As you seem to have a clue, could you please review

> > DDR3 on github.com/slapin/a13board ?
>
> As I didn't see any replies, maybe you could elaborate where you
> yourself see issues in your design. For example, knowing that Kicad
> doesn't have any helpers/checks for track length matching, I thought
> that writing a standalone tool to do post-check would be useful, but
> turned out that it's exactly what you have with your nets.py


Hi Paul,
       nets.py helps checking the data line lengths. But the net length
information about address/control lines does not help, they are branching
to  each memory chip and length of each branch need to be matched
separately.  Fortunately kicad displays the length of each branch when you
click on it. Is there any tool to list that also.



> 2. What about 2-layer board? I know, I know, they say that you at least
> should have GND layer between top and bottom signal layer. But well,
>

Even if you ignore the ground plane issue, 2 layers is almost impossible. 4
layer is fine if we ignore the ground, 2 are ground only in the 6layer
board i tried.

ajith




> there's no GND layer between signals on the same layer (though they
> recommend routing GND track between signals, yeah!). And generally,
> that "you need at least 4 layers" comes from the same industrial
> pundits who then put DIMM sockets on motherboards (whoa, those
> mechanical contacts must have crazy impedance and capacitance, and yet
> it works), and who's going to stop marking SMD resistors to "save
> environment", in other words, that can be yet another industrial B/S.
>
> 3. Generally, I wonder if A13 can be made to work with classy DDR after
> all. The idea is not to chase for "highest throughput" design
> (Allwinner is not such anyway), but to have really personal-fab board
> for router and similar usages. And real slowness is always in software.
>
>
> >
> > Thanks a lot,
> > S.
> >
>
> --
> Best regards,
>  Paul                          mailto:pmiscml at gmail.com
>
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-- 
Dr. Ajith Kumar B.P.
Scientist SH
Inter-University Accelerator Centre
Aruna Asaf Ali Marg
New Delhi 110067
www.iuac.res.in
Ph: (off) 91 11 26893955 (Ext.230)
      (res)91 11 26897867
      (mob) 91 9868150852
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