21-03-2017, 08:26 AM
I've nver used Altera FPGAs so am unfamiliar with their capabilities. I assume they must be comparable to what Xilinx parts can do in any given generation and cost but with many difference of detail.
You say you multiplied the 50MHz clock up to 150MHz using a PLL within the FPGA. If the PLL can do it there's probably no harm going up to 200MHz or even higher. Again I don't know how fast the logic will run but you're only talking about a very small amount running at that frequency. Again this will vary with the FPGA make and family, but you should put some kind of timing specification when running fast logic. This is to ensure that it will actually run at that speed. Again detail will differ between Altera and Xilinx tools.
My own experience in Xilinx Spartan 3A devices is that 54MHz might as well be DC - it would be hard to design something that failed at 54MHz unless you were cascading loads of combinatorial logic without registers. At 148.5MHz I needed to take great care with pieplining to meet timespecs. The other factor is how full the device is. It's easy to get high speed in a lightly utilised device. Experience is really the only way to get a feel for this.
You say you multiplied the 50MHz clock up to 150MHz using a PLL within the FPGA. If the PLL can do it there's probably no harm going up to 200MHz or even higher. Again I don't know how fast the logic will run but you're only talking about a very small amount running at that frequency. Again this will vary with the FPGA make and family, but you should put some kind of timing specification when running fast logic. This is to ensure that it will actually run at that speed. Again detail will differ between Altera and Xilinx tools.
My own experience in Xilinx Spartan 3A devices is that 54MHz might as well be DC - it would be hard to design something that failed at 54MHz unless you were cascading loads of combinatorial logic without registers. At 148.5MHz I needed to take great care with pieplining to meet timespecs. The other factor is how full the device is. It's easy to get high speed in a lightly utilised device. Experience is really the only way to get a feel for this.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
