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author | Clifford Wolf <clifford@clifford.at> | 2015-06-06 21:27:58 +0200 |
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committer | Clifford Wolf <clifford@clifford.at> | 2015-06-06 21:27:58 +0200 |
commit | 90ff3380a4e24762b6dd78ad86fc1beddd44f279 (patch) | |
tree | 42ea6321b3cafe5e6058102874136c9dd7f646d6 | |
parent | 2107a328c4d1fe406791dc4c53ea49e246f0ef6c (diff) | |
download | picorv32-90ff3380a4e24762b6dd78ad86fc1beddd44f279.tar.gz picorv32-90ff3380a4e24762b6dd78ad86fc1beddd44f279.zip |
Updated README
-rw-r--r-- | README.md | 22 |
1 files changed, 16 insertions, 6 deletions
@@ -13,7 +13,7 @@ PicoRV32 is free and open hardware licensed under the [ISC license](http://en.wi Features and Typical Applications: ---------------------------------- -- Small (about 1000 LUTs in a 7-Series Xilinx FGPA) +- Small (~1000 LUTs in a 7-Series Xilinx FGPA) - High fMAX (>250 MHz on 7-Series Xilinx FGPAs) - Selectable native memory interface or AXI4-Lite master @@ -46,12 +46,22 @@ interface, and communicating with the outside world via AXI4. Performance: ------------ -The average Cycles per Instruction (CPI) is 6 to 8, depending on the -application code. (Most instructions, including unconditional branches and -not-taken conditional branches execute in 5 cycles. Memory load/store, taken -conditional branches, JALR, and shift operations may take more than 5 cycles.) +The average Cycles per Instruction (CPI) is 5 to 7, depending on the +mix of instructions in the code. The CPI for the individual instructions is: -Dhrystone benchmark results: 0.124 DMIPS/MHz (219 Dhrystones/Second/MHz) +| Instruction | CPI | +| ------------------- | ---:| +| ALU reg + immediate | 4 | +| ALU reg + reg | 5 | +| memory load | 7 | +| memory store | 8 | +| branch, taken | 8 | +| branch, not taken | 5 | +| shift operations | 5+ | + +Dhrystone benchmark results: 0.146 DMIPS/MHz (258 Dhrystones/Second/MHz) + +For the Dryhstone benchmark the average CPI is 6.181. *This numbers apply for setups with memory that can accomodate requests within one clock cycle. Slower memory will degrade the performance of the processor.* |