B3 with different RAM chips

[John Watlington]

Trac it.

No, we have seen nothing that leads us to believe that we have
memory corruption problems w. B2s.   Software errors are a much
more likely cause.

wad

On Nov 23, 2009, at 6:56 PM, Tiago Marques wrote:

> On Mon, Nov 23, 2009 at 7:19 PM, John Watlington <wad at laptop.org>  
> wrote:
>>
>> On Nov 23, 2009, at 1:55 PM, Tiago Marques wrote:
>>
>>> On Sun, Nov 22, 2009 at 8:01 PM, Mitch Bradley <wmb at laptop.org>  
>>> wrote:
>>>>
>>>> Tiago Marques wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> 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.
>>>>
>>>> CL3 is in spec for the chips that we were using but not for a  
>>>> new chip
>>>> that
>>>> we might start using.
>>>>
>>>>> Are you running at 400 or 533?
>>>>
>>>> 400
>>>>>
>>>>> Doesn't the datasheet specify the appropriate timings?
>>>>>
>>>>
>>>> Of course it does.  The jumper is to tell which timing set to use,
>>>> depending
>>>> on which chips are populated.
>>>
>>> Ok, I was rather confused when I read:
>>>
>>> "I switched the timing to CAS latency 4 (from 3), which ** should  
>>> meet
>>> ** specs for this chip."
>>>
>>> And was finding rather odd that you didn't had access to specified
>>> timings.
>>
>> We have access to the chip timings, and we have information about how
>> to program the controller.   But it is still a trial and error  
>> process.
>> Nobody likes to manually verify that the programmable DRAM  
>> controller is
>> actually correctly generating the literally hundreds of timing  
>> specs for a
>> given chip.  We instead make our best guess at correct values and  
>> then
>> test for proper operation across time and temperature.
>>
>> In this case, the chips usually worked with the CAS latency set  
>> too low.
>>
>> wad
>>
>>
>
> Ok, I see. Any chance that that procedure might be causing issues
> related to those errors being generated by overheating problems with
> B2 hardware? I haven't heard if that has been fixed already. Was it?
> My 1.5 B2 crashed yesterday in a rather unexplicable fashion and gave
> me some bad data corruption. Haven't been able to reproduce it though,
> but it seemed high workload related since I was compiling some
> packages on an FS in the external SD. Will try to find out more about
> this.
>
> Best regards,
> Tiago Marques
>