Hi, I have seen contradictory data about speed of GTX transceivers in Kintex 7 in FBG packages: 1. The datasheet ( http://www.xilinx.com/support/documentation/data_sheets/ds182_Kintex_7_Data_Sheet.pdf , page 54 ) states that the maximum speed is 6.6 Gb/s 2. The answer record http://www.xilinx.com/support/answers/50299.html states explicitly: " Limit the maximum line rate to 6.6 Gb/s if you need the core files for an FBG package, even if the GUI allows for a higher line rate (For Kintex-7 devices the maximum line rate is not dependent on package type and can be up to 12.5 Gb/s for all packages while in Zynq it is limited to 6.6 Gb/s for FBG packages and is 12.5 Gb/s for FFG packages)." I haven't seen any warnings about rate limit in FB... packages in product selection guides like http://www.xilinx.com/publications/prod_mktg/7-series-product-selection-guide.pdf or http://www.xilinx.com/products/silicon-devices/fpga/kintex-7.html#producttable I have tested a board, which was supposed to be assembled with xc7k325t_ffg900 chip, but due to a mistake an xc7k325t_fbg900 was used (chip was hidden under the heat sink, and in JTAG there is no difference between those chips) The board worked perfectly at full speed with 10 Gbps links. Does anybody has an information if this speed limit for FB package really exists, and what is its reason? I can see two possible reasons: 1. Signal integrity. I know that there are differences between wire-bond and flip-chip packages (but AFAIK both FB and FF are flip-chip) 2. Heat dissipation. At 10 Gbps the link may dissipate more power than at 6.6 Gbps. But does FB have higher thermal resistance than the FF one? The difference between the two above is significant. In case 1 - if the board happened to work and Eye Diagram is good, it can be reliably used. In case 2 - the board may work with link test only, but when we add additional processing blocks it may get overheated... Thank you in advance, Best regards, Wojtek PS. This qustion was also asked on Xilinx forum: http://forums.xilinx.com/t5/7-Series-FPGAs/Speed-of-GTX-transceivers-in-Kintex-7-in-FBG-package/m-p/638015#M12356 With best regards, Wojtek
Speed of GTX transceivers in Kintex 7 in FBG package?
Started by ●June 25, 2015