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AMCC suggested to set the PMU bit to 0 for best performace on the PPC440 DDR controller. The 440er common DDR setup files (sdram.c & spd_sdram.c) are changed accordingly. So all 440er boards using these setup routines will automatically receive this performance increase. Please see below some benchmarks done by AMCC to demonstrate this performance changes: ---------------------------------------- SDRAM0_CFG0[PMU] = 1 (U-Boot default for Bamboo, Yosemite and Yellowstone) ---------------------------------------- Stream benchmark results ------------------------------------------------------------- This system uses 8 bytes per DOUBLE PRECISION word. ------------------------------------------------------------- Array size = 2000000, Offset = 0 Total memory required = 45.8 MB. Each test is run 10 times, but only the *best* time for each is used. ------------------------------------------------------------- Your clock granularity/precision appears to be 1 microseconds. Each test below will take on the order of 112345 microseconds. (= 112345 clock ticks) Increase the size of the arrays if this shows that you are not getting at least 20 clock ticks per test. ------------------------------------------------------------- WARNING -- The above is only a rough guideline. For best results, please be sure you know the precision of your system timer. ------------------------------------------------------------- Function Rate (MB/s) RMS time Min time Max time Copy: 256.7683 0.1248 0.1246 0.1250 Scale: 246.0157 0.1302 0.1301 0.1302 Add: 255.0316 0.1883 0.1882 0.1885 Triad: 253.1245 0.1897 0.1896 0.1899 TTCP Benchmark Results ttcp-t: socket ttcp-t: connect ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=5000 tcp -> localhost ttcp-t: 16777216 bytes in 0.28 real seconds = 454.29 Mbit/sec +++ ttcp-t: 2048 I/O calls, msec/call = 0.14, calls/sec = 7268.57 ttcp-t: 0.0user 0.1sys 0:00real 60% 0i+0d 0maxrss 0+2pf 3+1506csw ---------------------------------------- SDRAM0_CFG0[PMU] = 0 (Suggested modification) Setting PMU = 0 provides a noticeable performance improvement *2% to 5% improvement in memory performance. *Improves the Mbit/sec for TTCP benchmark by almost 76%. ---------------------------------------- Stream benchmark results ------------------------------------------------------------- This system uses 8 bytes per DOUBLE PRECISION word. ------------------------------------------------------------- Array size = 2000000, Offset = 0 Total memory required = 45.8 MB. Each test is run 10 times, but only the *best* time for each is used. ------------------------------------------------------------- Your clock granularity/precision appears to be 1 microseconds. Each test below will take on the order of 120066 microseconds. (= 120066 clock ticks) Increase the size of the arrays if this shows that you are not getting at least 20 clock ticks per test. ------------------------------------------------------------- WARNING -- The above is only a rough guideline. For best results, please be sure you know the precision of your system timer. ------------------------------------------------------------- Function Rate (MB/s) RMS time Min time Max time Copy: 262.5167 0.1221 0.1219 0.1223 Scale: 258.4856 0.1238 0.1238 0.1240 Add: 262.5404 0.1829 0.1828 0.1831 Triad: 266.8594 0.1800 0.1799 0.1802 TTCP Benchmark Results ttcp-t: socket ttcp-t: connect ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=5000 tcp -> localhost ttcp-t: 16777216 bytes in 0.16 real seconds = 804.06 Mbit/sec +++ ttcp-t: 2048 I/O calls, msec/call = 0.08, calls/sec = 12864.89 ttcp-t: 0.0user 0.0sys 0:00real 46% 0i+0d 0maxrss 0+2pf 120+1csw 2006-07-28, Stefan Roese <sr@denx.de>