NaxRiscv
An RISC-V core currently characterised by :
- Out of order execution with register renaming
- Superscalar (ex : 2 decode, 3 execution units, 2 retire)
- (RV32/RV64)IMAFDCSU (Linux / Buildroot works on hardware)
- High perf config : 2.93 DMIPS/Mhz, 5.02 Coremark/Mhz, 1.67 Embench-iot baseline (Cortex M4) @ 155 Mhz + 13.3 KLUT on Artix 7-3
- Portable HDL, but target FPGA with distributed ram (Xilinx series 7 is the reference used so far)
- Target a (relatively) low area usage and high fmax (not the best IPC)
- Decentralized hardware elaboration (Empty toplevel parametrized with plugins)
- Frontend implemented around a pipelining framework to ease customisation
- Non-blocking Data cache with multiple refill and writeback slots
- BTB + GSHARE + RAS branch predictors
- Hardware refilled MMU (SV32, SV39)
- Load to use latency of 3 cycles via the speculative cache hit predictor
- Pipeline visualisation via verilator simulation and Konata (gem5 file format)
- JTAG / OpenOCD / GDB support by implementing the RISCV External Debug Support v. 0.13.2
To test the project, see the "Running Verilator simulation" section
Online documentation
There is a Read The Doc hosted here :
https://spinalhdl.github.io/NaxRiscv-Rtd/main/NaxRiscv/introduction/index.html
Performances / Area
See :
https://spinalhdl.github.io/NaxRiscv-Rtd/main/NaxRiscv/performance/index.html
Running on hardware
NaxRiscv is currently integrated into https://github.com/enjoy-digital/litex. For instance to run it on the Nexys video board, you can :
python3 -m litex_boards.targets.digilent_nexys_video --cpu-type=naxriscv --with-video-framebuffer --with-sdcard --build --loadAlso, note that if you want to run linux on it, it is image compatible with https://github.com/litex-hub/linux-on-litex-vexriscv, you will have to adapte the dts/dtb (removing peripherals).
Here is Doom running in linux : https://twitter.com/enjoy_digital/status/1493996880593887235?s=20&t=VR734wYewBFsT2Fgvm339Q
Running Verilator simulation
See src/test/cpp/naxriscv/README.md
Linux/Buildroot running in simulation :
./obj_dir/VNaxRiscv \
--load-bin $LINUX_IMAGES/fw_jump.bin,0x80000000 \
--load-bin $LINUX_IMAGES/linux.dtb,0x80F80000 \
--load-bin $LINUX_IMAGES/Image,0x80400000 \
--load-bin $LINUX_IMAGES/rootfs.cpio,0x81000000
OpenSBI v0.8
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| | | | '_ \ / _ \ '_ \ \___ \| _ < | |
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\____/| .__/ \___|_| |_|_____/|____/_____|
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Platform Name : NaxRiscv
Platform Features : timer,mfdeleg
Platform HART Count : 1
Boot HART ID : 0
Boot HART ISA : rv32imasu
BOOT HART Features : scounteren,mcounteren
BOOT HART PMP Count : 0
Firmware Base : 0x80000000
Firmware Size : 64 KB
Runtime SBI Version : 0.2
MIDELEG : 0x00000222
MEDELEG : 0x0000b109
[ 0.000000] Linux version 5.10.1 (rawrr@rawrr) (riscv32-buildroot-linux-gnu-gcc.br_real (Buildroot 2020.11-rc3-8-g9ef54b7d0b) 10.2.0, GNU ld (GNU Binutils) 2.34) #2 SMP Wed Jan 26 14:18:17 CET 2022
[ 0.000000] earlycon: sbi0 at I/O port 0x0 (options '')
[ 0.000000] printk: bootconsole [sbi0] enabled
[ 0.000000] Initial ramdisk at: 0x(ptrval) (8388608 bytes)
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000080400000-0x000000008fffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000080400000-0x000000008fffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000080400000-0x000000008fffffff]
[ 0.000000] SBI specification v0.2 detected
[ 0.000000] SBI implementation ID=0x1 Version=0x8
[ 0.000000] SBI v0.2 TIME extension detected
[ 0.000000] SBI v0.2 IPI extension detected
[ 0.000000] SBI v0.2 RFENCE extension detected
[ 0.000000] SBI v0.2 HSM extension detected
[ 0.000000] riscv: ISA extensions aim
[ 0.000000] riscv: ELF capabilities aim
[ 0.000000] percpu: Embedded 10 pages/cpu s18700 r0 d22260 u40960
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 64008
[ 0.000000] Kernel command line: rootwait console=hvc0 earlycon=sbi root=/dev/ram0 init=/sbin/init
[ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes, linear)
[ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
[ 0.000000] Sorting __ex_table...
[ 0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[ 0.000000] Memory: 241280K/258048K available (4717K kernel code, 553K rwdata, 632K rodata, 166K init, 213K bss, 16768K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] rcu: Hierarchical RCU implementation.
[ 0.000000] rcu: RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=1.
[ 0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[ 0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
[ 0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
[ 0.000000] riscv-intc: 32 local interrupts mapped
[ 0.000000] random: get_random_bytes called from start_kernel+0x35c/0x4dc with crng_init=0
[ 0.000000] riscv_timer_init_dt: Registering clocksource cpuid [0] hartid [0]
[ 0.000000] clocksource: riscv_clocksource: mask: 0xffffffffffffffff max_cycles: 0x171024e7e0, max_idle_ns: 440795205315 ns
[ 0.000096] sched_clock: 64 bits at 100MHz, resolution 10ns, wraps every 4398046511100ns
[ 0.001452] Console: colour dummy device 80x25
[ 0.001923] printk: console [hvc0] enabled
[ 0.001923] printk: console [hvc0] enabled
[ 0.002597] printk: bootconsole [sbi0] disabled
[ 0.002597] printk: bootconsole [sbi0] disabled
[ 0.003469] Calibrating delay loop (skipped), value calculated using timer frequency.. 200.00 BogoMIPS (lpj=400000)
[ 0.004346] pid_max: default: 32768 minimum: 301
[ 0.006040] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[ 0.006715] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[ 0.018275] rcu: Hierarchical SRCU implementation.
[ 0.021169] smp: Bringing up secondary CPUs ...
[ 0.021752] smp: Brought up 1 node, 1 CPU
[ 0.024190] devtmpfs: initialized
[ 0.029478] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[ 0.030479] futex hash table entries: 256 (order: 2, 16384 bytes, linear)
[ 0.032419] NET: Registered protocol family 16
[ 0.072397] clocksource: Switched to clocksource riscv_clocksource
[ 0.130361] NET: Registered protocol family 2
[ 0.135484] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144 bytes, linear)
[ 0.136588] TCP established hash table entries: 2048 (order: 1, 8192 bytes, linear)
[ 0.137670] TCP bind hash table entries: 2048 (order: 2, 16384 bytes, linear)
[ 0.138674] TCP: Hash tables configured (established 2048 bind 2048)
[ 0.139694] UDP hash table entries: 256 (order: 1, 8192 bytes, linear)
[ 0.140653] UDP-Lite hash table entries: 256 (order: 1, 8192 bytes, linear)
[ 0.145111] Unpacking initramfs...
[ 0.382796] Initramfs unpacking failed: invalid magic at start of compressed archive
[ 0.438458] Freeing initrd memory: 8192K
[ 0.442311] workingset: timestamp_bits=30 max_order=16 bucket_order=0
[ 0.497197] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 254)
[ 0.497827] io scheduler mq-deadline registered
[ 0.498260] io scheduler kyber registered
[ 0.863943] NET: Registered protocol family 10
[ 0.869801] Segment Routing with IPv6
[ 0.870713] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[ 0.875543] NET: Registered protocol family 17
[ 0.880356] Freeing unused kernel memory: 164K
[ 0.880786] Kernel memory protection not selected by kernel config.
[ 0.881380] Run /init as init process
Starting syslogd: OK
Starting klogd: OK
Running sysctl: OK
Saving random seed: [ 1.502669] random: dd: uninitialized urandom read (512 bytes read)
OK
Starting network: OK
Welcome to Buildroot
buildroot login: root
_ _ ___ _
o O O | \| | __ _ __ __ | _ \ (_) ___ __ __ __
o | .` | / _` | \ \ / | / | | (_-< / _| \ V /
TS__[O] |_|\_| \__,_| /_\_\ |_|_\ _|_|_ /__/_ \__|_ _\_/_
{======|_|"""""|_|"""""|_|"""""|_|"""""|_|"""""|_|"""""|_|"""""|_|"""""|
./o--000'"`-0-0-'"`-0-0-'"`-0-0-'"`-0-0-'"`-0-0-'"`-0-0-'"`-0-0-'"`-0-0-'
login[65]: root login on 'console'
root@buildroot:~# cat /proc/cpuinfo
processor : 0
hart : 0
isa : rv32ima
mmu : sv32
root@buildroot:~# echo 1+2+3*4 | bc
15
root@buildroot:~# micropython
MicroPython v1.13 on 2022-01-26; linux version
Use Ctrl-D to exit, Ctrl-E for paste mode
>>> 1+2+3
6
>>> import math
>>> math.sin(math.pi/4)
0.7071067811865475
>>> from sys import exit
>>> exit()
root@buildroot:~# ls /
bin init linuxrc opt run tmp
dev lib media proc sbin usr
etc lib32 mnt root sys var
root@buildroot:~#