On Sun, Nov 22, 2009 at 8:01 PM, Mitch Bradley <[email protected]> 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. Best regards, Tiago Marques > >> Best regards >> >> On Fri, Nov 20, 2009 at 8:21 PM, John Watlington <[email protected]> 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. >>> >>> wad >>> >>> 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. >>>> >>> >>> _______________________________________________ >>> Devel mailing list >>> [email protected] >>> http://lists.laptop.org/listinfo/devel >>> >>> > _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
