#11918 NORM 11.3.1: Nanya/Micron 2Gb DRAM doesn't work

[Zarro Boogs per Child]

#11918: Nanya/Micron 2Gb DRAM doesn't work
---------------------------------+------------------------------------------
 Reporter:  wad                  |                 Owner:  wmb at firmworks.com
     Type:  defect               |                Status:  new              
 Priority:  normal               |             Milestone:  11.3.1           
Component:  ofw - open firmware  |               Version:  1.75-C1          
 Keywords:  XO-1.75              |           Next_action:  code             
 Verified:  0                    |   Deployment_affected:                   
Blockedby:                       |              Blocking:                   
---------------------------------+------------------------------------------
 When testing the latest 2Gb DD3 die from Nanya (NT5CB256M8GN-CG), which is
 also shipped as Micron's MT4J256M8HX-15E, memory errors prevented a
 current OFW from booting.

 Further examination showed that our existing memory timing is not valid
 for those parts.   Per JEDEC JESD-79-3D ( http://www.jedec.org/standards-
 documents/docs/jesd-79-3d ), 2Gb parts are allowed to have a longer tRFC
 than used by our current timing.

 We haven't seen a problem with already qualified 2Gb parts, but those will
 probably be EOL'd soon in favor of newer dies.

 I suggest that CForth's memory configuration code be changed to include
 conditional setting of register 0xd0000060 to 0x64660404 (instead of
 0x646602C4) when configuring 1GB of memory.

 This value meets the JEDEC requirements, and has been tested to work with
 the Nanya memory.   It appears both Micron test boards had rework
 problems, and haven't been tested yet.

 Before releasing this modification, we should test with all qualified 2Gb
 parts.  It is expected, however, that even 1Gb parts should work with this
 more conservative timing.

-- 
Ticket URL: <http://dev.laptop.org/ticket/11918>
One Laptop Per Child <http://laptop.org/>
OLPC bug tracking system