Can't place all RAM cells in design
在熟悉新环境的qsys，建完nios cpu后，在quartus下编译时报错：
Error (170040): Can't place all RAM cells in design
Info (170034): Selected device has 30 memory locations of type M9K. The current design requires 50 memory locations of type M9K to successfully fit.Info (170033): Memory usage required for the design in the current device: 167% M9K memory block locations required
Info (170190): Fitter placement preparation operations ending: elapsed time is 00:00:01
Info (11888): Total time spent on timing analysis during the Fitter is 0.03 seconds.
Error (171000): Can't fit design in device
Info (144001): Generated suppressed messages file E:/working/Beijing/trials/qsys_led/output_files/hello_led.fit.smsg
Error: Quartus II 64-Bit Fitter was unsuccessful. 2 errors, 8 warnings
Error: Peak virtual memory: 749 megabytes
Error: Processing ended: Tue Jan 21 01:27:09 2014
Error: Elapsed time: 00:00:12
Error: Total CPU time (on all processors): 00:00:11
Error (293001): Quartus II Full Compilation was unsuccessful. 4 errors, 61 warnings
原因大概是我在建nios cpu里面的onchip memory的时候大小填了40960 bytes，太大了，FPGA放不下。
回去改回4096 bytes。update bdf文件。重新编译。通过。