PPC440 DDR setup: Set SDRAM0_CFG0[PMU]=0 for best performance
AMCC suggested to set the PMU bit to 0 for best performace on
the PPC440 DDR controller.
Please see doc/README.440-DDR-performance for details.
Patch by Stefan Roese, 28 Jul 2006
diff --git a/doc/README.440-DDR-performance b/doc/README.440-DDR-performance
new file mode 100644
index 0000000..17bc747
--- /dev/null
+++ b/doc/README.440-DDR-performance
@@ -0,0 +1,90 @@
+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>