Chip stocks are back in a bull market after spending just 21 days in bear market territory but the biggest riser as it came out may come as a bit of a surprise - Credo Technology.

That's where the good news ends as semiconductor companies were falling sharply ahead of the open Tuesday amid higher oil prices and bond yields. Big winners from its rapid bear market escape-Intel, Micron, Coherent and Marvell were all down more than 5%.

The PHLX Semiconductor Index, SOX, has jumped 21% since its July 29 low, through Monday's close-meeting the definition of a new bull market run. It's the sector's sharpest exit from a bear market since March 2020, and far shorter than the average 54 days, according to Dow Jones Market Data.

But the stand out star was unexpected. Credo Technology, the maker of copper cables used to connect AI servers, has surged 59% since July 29, narrowly beating optical networking company Coherent's 58% jump. Credo stock was also falling around 5% in premarket trading.

All the big names have enjoyed sizable gains over that period-Nvidia has jumped 18%, Intel has climbed 26% and Micron is up 37%.

It looks like a shaky start to life in a new bull market for the volatile sector.