VR Zone reports Intel has cancelled the 3.4W L3510H "Cactus Ridge" Thunderbolt chip in favor of the 2.8W L3510L chip. Final samples of the chip are anticipated by mid-April, about four weeks later than previously announced.
However, the delay of the Thunderbolt chip shouldn't have a huge effect on actual products because of Ivy Bridge's delay.
Technically there is no different between the 3.4W TDP L3510H and the 2.8W L3510L Cactus Ridge Thunderbolt chips, although we presume that Intel was planning on charging more for the lower power part as it would've been targeting the notebook market space with the 3.4W part going into desktops and powered devices.
The L3510 is a 4-channel Thunderbolt controller and it's set to replace the original Thunderbolt controller known as Light Ridge or 82523EF/EFL which launched towards the end of 2010. The L3510 is a smaller 12x12mm chip – compared to 15x15mm for Light Ridge – and with the changes it's also slightly more power efficient. Intel has also managed to implement additional features on-chip for Cactus Ridge, such as a DisplayPort redriver, a connection manager and a link controller which should help drive down the cost of implementing Thunderbolt as well as help to reduce the PCB space taken up by the components needed.