add sbi spec

diff --git a/3d_gpu.mdwn b/3d_gpu.mdwn
index 6885727de3fea1c15694d23cfca5bfab1ad549cb..ee19acabfc4af2dd13944f2d72a1c6326890c953 100644 (file)
--- a/3d_gpu.mdwn
+++ b/3d_gpu.mdwn
@@ -72,6 +72,7 @@ Progress:
 * <https://en.wikipedia.org/wiki/Liskov_substitution_principle>
 * <https://en.wikipedia.org/wiki/Principle_of_least_astonishment>
 * <https://peertube.f-si.org/videos/watch/379ef007-40b7-4a51-ba1a-0db4f48e8b16>
+* <https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.md>
 
 # Analog Simulation