B3 with different RAM chips

John Watlington wad at laptop.org
Fri Nov 20 15:21:29 EST 2009

I suggest that we dedicate the unused
memory ID 0 jumper (GPIO9) to indicate that
this DRAM is present.

Thanks for reminding me, as Richard and I
wanted to add another jumper since we've used
them all up.


On Nov 20, 2009, at 2:51 AM, Mitch Bradley wrote:

> I have a B3 with 1 GiB of memory, using Samsung K4T1G084QE RAM chips
> which have slightly different timing than the chips we were using.
> Using the old timings, it booted Open Firmware and appeared to  
> work, but
> memtest quickly elicited errors - it started showing them after  
> about 20
> seconds, during test #2, moving inversions with a constant pattern.
> I switched the timing to CAS latency 4 (from 3), which should meet  
> specs
> for this chip.  memtest has been running for 7 minutes with no errors.
> I'll leave it running overnight.
> If we are to use this chip, we'll need a way to identify it - perhaps
> one of the memory ID straps - unless we want to run the other chips at
> CL4 too.
> CL4 has little or no effect on the memcpy speed, but it would slow  
> down
> random reads to a small extent.

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