Shorts and open circuits on high-speed serdes buses, such as PCI Express, may have subtle and difficult-to-diagnose effects on system performance. In other words, you might not know about them until customers start complaining and you get warranty returns. What kind of effects are these, and how are they prevented?
One of the biggest design challenges today revolves around maintaining signal integrity in the presence of power and ground rail fluctuations due to simultaneously switching signals. This is particularly true for DDR4 memory.
Not all memories are created equal. Some DIMM suppliersโ cards have margins that are better than others. And of course, the better the margins, the better the performance of the system, and the fewer blue screens.
In early 2011, Intel discovered a design issue on their Cougar Point chipset, and took an approximately $700 million charge against earnings to repair and replace affected parts and systems. What may have been the root cause of this, and how may it have been prevented?
In my previous blog I covered at a high level why system signal integrity is highly dependent upon the silicon. Letโs dive into this a little deeper by first looking at wafer and die manufacturing variances.
I was asked recently whether engineers could just check the CRC error counts coming from the Operating System to ensure they had good signal integrity and operating margins. After all, a CRC checks for bit errors, right? Hereโs why this is not good enough: