add link to gdb mirror

diff --git a/HDL_workflow.mdwn b/HDL_workflow.mdwn
index 95600f05fb7f59781d9e15a2d30150068d220d80..95ec794940732c029bea9f90a2560984606c4da5 100644 (file)
--- a/HDL_workflow.mdwn
+++ b/HDL_workflow.mdwn
@@ -439,7 +439,9 @@ Install qemu:
 
     apt-get install qemu-system-ppc
 
-Install gdb from source.  Obtain the latest tarball, unpack it, then:
+Install gdb from source.  Obtain the required tarball matching
+the version of gcc (9.1) from here <https://ftp.gnu.org/gnu/gdb/>,
+unpack it, then:
 
     cd gdb-9.1 (or other location)
     mkdir build