September 5th, 2008


The how and why of NVidia's defective GPUs.

The defective parts appear to make up the entire line-up of Nvidia parts on 65nm and 55nm processes, no exceptions. The question is not whether or not these parts are defective, it is simply the failure rates of each line, with field reports on specific parts hitting up to 40 per cent early life failures. This is obviously not acceptable.

The part [of a chip] you don't see are the bumps, and they are the most critical part. This type of packaging is called flip-chip because the connectors between the die and the substrate are put on the bottom of the die, then the die is flipped over onto the substrate. The connectors are called bumps, and they are literally little balls of solder. A typical chip that is a little more than a centimetre on a side might have over 1000 bumps on it, so spacing is incredibly small and tolerances amazingly tight.

The bumps act like pins on a normal chip, they carry signals, power and ground to and from the die. They also are the primary attachment mechanism of the die to the substrate. The precision needed to put these things together should not be underestimated. Some bumps may pull a lot of Amps, others may pull very few, and this again changes over time and use. The bumps also have a limited current capacity each, too much and they melt or burn out, so there are far more than are strictly needed to supply the chip with power.

The Nvidia defective chips use a type of bump called high lead, and are now transitioning to a type called eutectic. Eutectic materials have two important properties, they have a low melting point, and all components crystallize at the same temperature. This means they are easier to work with, and form a good solid bond. Eutectic bumps may have lead in them, or they may not, some are gold/tin, other are lead based, it depends on what characteristics you want, and how much you want to pay. It is a property, not a formula.

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"Not an angel"

Bobcats take over foreclosed houses in LA.

The foreclosure market is getting wild in Lake Elsinore: "Taking advantage of a slump in local real estate, a family of bobcats has moved into a foreclosed Lake Elsinore home, lolling about on fences and walls and riveting an entire neighborhood."

More, from the L.A. Times' David Kelly:

Neighbors first noticed the feline squatters Aug. 27 hanging out on a side wall of the empty house in the Tuscany Hills development.... The foreclosed home is one of several on the block. Its lawn is brown but still being watered by the sprinklers. The house sits right up against barren, chaparral-covered hills. At least two adult bobcats and perhaps a litter of young ones appear to be occupying the house. Residents have mixed emotions about their new neighbors.

Bottomfisher wrote, "They could have easily qualified for a loan last they just squat."

Gary in Marysville Michigan wrote, "Someone should notify the DEA. They could be guarding a major catnip growing operation."