readme

readme.md

@@ -0,0 +1,140 @@
+# A2P
+
+<img align="right" src="media/banner.png">
+
+## Back to the 90s!
+
+A2P is a mashup of OpenPOWER architecture and VexRiscv, creating a new 32b Power core for experimentation and lightweight designs.
+
+## Status
+
+### Function
+
+<img align="right" width="50%" src="media/sim.png">
+
+* Ops (100+) not thoroughly tested, but running a minimal kernel and partial Litex BIOS in Verilator and on FPGAs.  Likely still
+some bugs in CR/XER handling.
+
+* Need to define supported translation modes.
+
+* SOC builds with Litex; software is built manually and runs from 'ROM' with on-board RAM.
+
+* Core and SOC run in Verilator/pyverilator.  SOC uses emulated host UART.
+
+### FPGA Implementation
+
+* Currently using Cmod A7-35T board. 
+
+* Needs SOC code update to access external SRAM.  I2C works.
+
+<img width="50%" src="media/fpga.png">
+
+* A lot of LUTs are being used by bypass/GPR write.  Recent analysis (100MHz, Vivado/Artix):
+
+```
+cellanal.py
+
+--- cells_ff.txt ---
+
+Total: 1791
+
+IC                              115
+decode                          244
+execute                         456
+regfile                           0
+hazards                          38
+ALU2                             32
+MULDIV                          136
+memory                          295
+DC                               69
+SPR                             239
+MSR                              15
+writeBack                         1
+ibus                             32
+dbus                             32
+SPINAL _zz_                      87
+Total in matched areas         1791
+
+*** >32 bits (93): a2p_i/A2P_WB/inst/IBusCachedPlugin_fetchPc_pcReg_reg ***
+*** >32 bits (52): a2p_i/A2P_WB/inst/memory_to_writeBack_MUL_LOW_reg ***
+Totals by cells:
+    1: 131   131
+    2:  16   163
+    3:   7   184
+    4:   6   208
+    5:  18   298
+    6:   1   304
+    7:   1   311
+    8:   5   351
+   10:   1   361
+   11:   2   383
+   26:   1   409
+   30:   3   499
+   31:   5   654
+   32:  31  1646
+   52:   1  1698
+   93:   1  1791
+
+--- cells_lut.txt ---
+
+Total: 2539
+
+IC                               85
+decode                          262
+execute                        1758
+regfile                           9
+hazards                          35
+ALU2                              0
+MULDIV                          145
+memory                          133
+DC                                1
+SPR                              56
+MSR                               0
+writeBack                         0
+ibus                              1
+dbus                              8
+SPINAL _zz_                      46
+Total in matched areas         2539
+
+*** >32 bits (35): a2p_i/A2P_WB/inst/Hazards_writeBackBuffer_payload_data ***
+*** >32 bits (62): a2p_i/A2P_WB/inst/IBusCachedPlugin_fetchPc_pcReg_reg ***
+*** >32 bits (34): a2p_i/A2P_WB/inst/MULDIV1_result ***
+*** >32 bits (66): a2p_i/A2P_WB/inst/MULDIV_accumulator ***
+*** >32 bits (40): a2p_i/A2P_WB/inst/_zz_141_ ***
+*** >32 bits (42): a2p_i/A2P_WB/inst/decode_to_execute_RA ***
+*** >32 bits (220): a2p_i/A2P_WB/inst/decode_to_execute_RB ***
+*** >32 bits (107): a2p_i/A2P_WB/inst/execute_to_memory_BRANCH_CALC ***
+*** >32 bits (64): a2p_i/A2P_WB/inst/execute_to_memory_CR_WRITE_imm ***
+*** >32 bits (212): a2p_i/A2P_WB/inst/execute_to_memory_DECODER_stageables_49 ***
+*** >32 bits (1028): a2p_i/A2P_WB/inst/execute_to_memory_REGFILE_WRITE_DATA ***
+*** >32 bits (86): a2p_i/A2P_WB/inst/execute_to_memory_SRC_CR ***
+*** >32 bits (37): a2p_i/A2P_WB/inst/execute_to_memory_XER_WRITE_imm ***
+*** >32 bits (68): a2p_i/A2P_WB/inst/memory_to_writeBack_MUL_LOW ***
+Totals by cells:
+    1: 158   158
+    2:   1   160
+    3:   5   175
+    4:   1   179
+    5:   5   204
+    8:   2   220
+    9:   1   229
+   17:   1   246
+   20:   2   286
+   25:   1   311
+   31:   1   342
+   32:   3   438
+   34:   1   472
+   35:   1   507
+   37:   1   544
+   40:   1   584
+   42:   1   626
+   62:   1   688
+   64:   1   752
+   66:   1   818
+   68:   1   886
+   86:   1   972
+  107:   1  1079
+  212:   1  1291
+  220:   1  1511
+ 1028:   1  2539
+```