what's the mapping between speed grade(C6 C7 C8) and frequency?

[Altera_Forum]

altera device ,for example EP2C8Q208C8 and EP2C5T144C8 , are the fastest frequencies the same? Which frequencies the speed grade,C6\C7\C8 stand for? Different device,but the same speed grade,are their fastest frequencies the same?

[Altera_Forum]

Performance characteristics can be found in the Cyclone II datasheet: 

http://www.altera.com/literature/hb/cyc2/cyc2_cii5v1_01.pdf  beginning on page 5-15  Jake

[Altera_Forum]

I saw "Up to 260-MHz operation",but it don't mark the speed grade,Is the C8 grade can reach 260MHz or C6?  

Different device,but the same speed grade,are their fastest frequencies the same?

[Altera_Forum]

"Up to 260 MHz operation" is in the feature list near the beginning of the document. It is broken down into more detail, including speed grades starting at page 5-15 (page 104 in the PDF). 

 Asking for the maximum frequency supported on an FPGA is not as simple as a question as it may seem. The maximum frequency is very dependent on your design. The data sheet may mention 260 MHz, but most designs will probably not reach this.

[Altera_Forum]

Thank you.I know it. Different design,defferent frequency.