Hi, 2011/2/7 Joey Oravec <jora...@drewtech.com>: > Hi - > > I've been investigating a problem involving the at91sam9261 processor. > Across 2 or 3 years we've manufactured two products with: > > Crystal: 16.000 MHz > Processor Clock: 240 MHz (PLLA *15) > Master Clock: 120 MHz > VDDCORE: 1.2v > > Based on testing history, about 10% of the assemblies fail starting > above 30 degC. The simplest testcase to demonstrate is: 1) use uboot > relocated to SDRAM as normal 2) enable caches 3) fill 16mb of SDRAM with > a known pattern 4) use a test command to continually calculate and print > CRC. As you apply heat to the processor the testcase will print an > incorrect CRC. If the unit has not already crashed you can decrease the > temperature and see the correct CRC again, which demonstrates that SDRAM > hasn't flipped any bits. > > Extending ram timings or lowering master clock (ie. sdram bus clock) has > no impact. Lowering the processor clock to 224 MHz makes the problem go > away -- at this speed I can heat the processor to the rated 85 C and the > testcase above will not fail. Also replacing the processor usually makes > the problem go away. You won't see the problem with any variable > changed: caches disabled, any processor clock below 240 MHz, or VDDCORE > at 1.3v. > > I'm using PLL R/C calculated by the spreadsheet, and 240 MHz @ 1.2v > should be within spec up to 85 C. I've requested failure analysis on > some of the processors but I don't expect an answer any time soon. > > Is anybody else successful with a 240 MHz processor clock, or are you > using a lower processor clock for greater reliability? Can you recommend > any other diagnostics that might identify the root cause? In the > meantime for maximum reliability, I recommend using a processor clock > less than 240 MHz and checking your hardware with a similar testcase.
Funny... I always thought the Master-CLK could not go above 100MHz... I do not know the exact reason any more... Either way, we use it for several years now at 200/100Mhz with a 10MHz crystal. Anyway: This problem is not related to U-boot in any way, and is therefor OT. You should discuss this with Atmel. And some good news: We had a similar problem last year. I will explain off-list. Kind regards, Remy _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot