Re: Linux x uClinux for ColdFires: what is the best for what?

Bob Furber wrote:
> Commodity DDR and flash today comes in 0.8mm BGA packages

Yes, but these packages have split ball maps with a channel down the 
middle, making them not much harder to route to than a TSOP.

We don't really have the luxury of being able to implement routing 
channels like commodity memories.  If we were to go to sub-1 mm ball 
pitch, we need to incorporate routing channels by depopulating balls, 
and we'd likely end up in packages that are physically not much smaller 
than what we're doing with 1 mm ball pitch today.

Cost matters, too, and it's less expensive to assemble a 1 mm pitch BGA 
than it is a 0.8 mm pitch BGA.  For now, I most customers to whom I 
talk, even for high-volume applications, aren't requesting sub-1 mm 
pitches.  With our I/O counts in the 144 to 416 ball range, the coarser 
1 mm ball pitch seems to afford folks a little more leeway in escaping 
our ball maps out to the rest of the PCB within a reasonable number of 
layers.

That's not to say there aren't customers who are space constrained and 
asking for smaller packages, though.  There just aren't that many of 
them yet.

> While in this wishful thinking state of mind, I cannot help mentioning 
> my Technicolor dream: A new, compact, fast, low powered MPC55xx with 
> the PowerPC ripped out and replaced with a ColdFire or Arm core with 
> FlexBus LPDDR/DDR2 interface ..and, oh, yes, don't forget USB Host & 
> Device and 100/100 Ethernet and Phy ..all for < $50.

I don't see Ethernet PHYs getting integrated on-chip anymore.  They're 
not conducive to being designed in sub-0.18 micron process technologies, 
and they've recently become about as commoditized as RS-232 level shifters.

When I started work on the MCF5282, we were figuring $5 into the system 
cost for the PHY.  We've now reduced that to $1 to $2 depending on the 
target market.  That kind of cost erosion makes it difficult for us to 
recoup the costs of developing the PHY and integrating it.

BTW, I reserve the right to backtrack on this for Gbit Ethernet.  
There's some commonality between a GbE PHY and things like PCIe and SATA 
PHYs, which do get integrated, that might make this possible.  No 
promises, just an observation.
> b. Having tasted eTPU and MIOS on the MPC5xx, I got addicted.

eTPU...  We really have got the thumbscrews on you :-)

John

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