Hi,
I have seen contradictory data about speed of GTX transceivers in Kintex 7 in FBG packages:
- The datasheet ( formatting link, page 54 ) states that the maximum speed is
- The answer record formatting linkstate s explicitly: " Limit the maximum line rate to 6.6 Gb/s if you need the cor e 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 s election guides like
I have tested a board, which was supposed to be assembled with xc7k325t_ff g900 chip, but due to a mistake an xc7k325t_fbg900 was used (chip was hidd en under the heat sink, and in JTAG there is no difference between those ch ips) The board worked perfectly at full speed with 10 Gbps links.
Does anybody has an information if this speed limit for FB package really e xists, and what is its reason?
I can see two possible reasons:
- Signal integrity. I know that there are differences between wire-bond and flip-chip packages (but AFAIK both FB and FF are flip-chip)
- 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 b e reliably used.
In case 2 - the board may work with link test only, but when we add additio nal processing blocks it may get overheated...
Thank you in advance, Best regards,
Wojtek PS. This qustion was also asked on Xilinx forum:
With best regards,
Wojtek