B3 with different RAM chips
tiagomnm at gmail.com
Sun Nov 22 14:15:07 EST 2009
The hardware page for the XO 1.5 doesn't show the clockspeed of the
RAM chips used. CAS 3 looks like very aggressive timings for cheap
DDR2 chips. Are you running at 400 or 533? Doesn't the datasheet
specify the appropriate timings?
On Fri, Nov 20, 2009 at 8:21 PM, John Watlington <wad at laptop.org> wrote:
> 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
>> 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
>> random reads to a small extent.
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