A1989 (820-00850) RAMCFG

[HeyWatchOutDude]

Hi,

I have upgraded the RAM on a test machine from 8GB to 16GB (SKhynix 9CCNNNBJTAL). What is the correct MLB_RAMCFG strap setting for this configuration?

Proposed 16GB Config:

• MLB_RAMCFG0 = Low (1k ohm resistor to ground)
• MLB_RAMCFG1 = Low (1k ohm resistor to ground)
• MLB_RAMCFG2 = High (Pull-up / No resistor to ground)
• MLB_RAMCFG3 = Low (1k ohm resistor to ground)
• MLB_RAMCFG4 = Low (1k ohm resistor to ground)

Original 8GB Config:

• MLB_RAMCFG0 = High (Pull-up / No resistor to ground)
• MLB_RAMCFG1 = Low (1k ohm resistor to ground)
• MLB_RAMCFG2 = High (Pull-up / No resistor to ground)
• MLB_RAMCFG3 = Low (1k ohm resistor to ground)
• MLB_RAMCFG4 = Low (1k ohm resistor to ground)

 

[2informaticos]

RAMCFG0-2 look good (in theory).
RAMCFG3/4 should meet your chips specifications.

"MLB_RAMCFG2 = High (Pull-up / No resistor to ground)"
This looks strange, for original 8GB.
So we can never trust Apple...

 

[HeyWatchOutDude]

So it’s fine?

Proposed 16GB Config:

• MLB_RAMCFG0 = Low (1k ohm resistor to ground)
• MLB_RAMCFG1 = Low (1k ohm resistor to ground)
• MLB_RAMCFG2 = High (Pull-up / No resistor to ground)
• MLB_RAMCFG3 = Low (1k ohm resistor to ground)
• MLB_RAMCFG4 = Low (1k ohm resistor to ground)

 

[2informaticos]

Yes, test it at least.

The strange thing is that original configuration (8GB) you've found on the MLB, corresponds to Micron 16GB 2133MHz Die Rev A.

 

[SMMRepair]

The T2 chip on the board must support the increased RAM. This is a big issue on the 00850 because of how many T2 model chips there are. If the board you pull the RAM from doesn't have the identical-model T2, it won't work, even if you configure the CFG resistors properly.

 

[HeyWatchOutDude]

Yeah it has another T2 chip, thanks for bringing it up.