diff --git a/README.adoc b/README.adoc
index 8a7e770..9994ec5 100644
--- a/README.adoc
+++ b/README.adoc
@@ -10090,6 +10090,68 @@ Build the kernel with the <<gem5-arm-linux-kernel-patches>>, and then run:
 ;
 ....
 
+====== gem5 X86 multicore TimingSimpleCPU hangs
+
+Original report: https://stackoverflow.com/questions/56642695/a-working-linux-kernel-gem5-config-for-fs-boot-up-in-x86-smp/56644363#56644363
+
+At 08c79a194d1a3430801c04f37d13216cc9ec1da3:
+
+....
+./run --cpus 2 --emulator gem5 -- --cpu-type TimingSimpleCPU --caches --l2cache
+....
+
+Boot hangs, the last terminal message is:
+
+....
+pci 0000:00:04.0: legacy IDE quirk: reg 0x1c: [io  0x0376]
+....
+
+and a bit above we can see the suspicious message:
+
+....
+[Firmware Bug]: CPU1: APIC id mismatch. Firmware: 1 APIC: 0
+....
+
+====== gem5 ARM multicore HPI boot fails
+
+Original report: https://www.mail-archive.com/gem5-users@gem5.org/msg16677.html
+
+At d334a0db538db1a82db62fd5f74a169ca9e21f23 + 1:
+
+....
+/run --arch aarch64 --emulator gem5 --tmux --cpu 2 --run-id 2 -- --cpu-type=HPI --caches --l2cache --l1d_size=64kB --l1i_size=64kB --l2_size=256kB
+....
+
+The simulator fails with:
+
+....
+Exiting @ tick 18446744073709551615 because simulate() limit reached
+....
+
+and the last log message is:
+
+....
+<6>[    0.103629] printk: console [ttyAMA0] enabled
+....
+
+With 1 core, boot works, and the next message would have been:
+
+....
+<3>[    0.103586] OF: amba_device_add() failed (-2) for /kmi@1c070000
+....
+
+With `TimingSimpleCPU`, boot went further, also failed with those options just after init finished, the last message is:
+
+....
+root@buildroot#
+....
+
+and once again we have:
+
+....
+Exiting @ tick 18446744073709551615 because simulate() limit reached
+....
+
 ===== gem5 cache size
 
 https://stackoverflow.com/questions/49624061/how-to-run-gem5-simulator-in-fs-mode-without-cache/49634544#49634544