Comment 23 for bug 1778738

trusty before:
[...]
Calling hook amd64_microcode
Calling hook compcache
[...]
Calling hook intel_microcode
intel-microcode: adding microcode for currently online and selected Intel processors
intel-microcode: using early initramfs microcode update mode...
[...]

(that is, no amd, only current intel)

install versions from proposed:
[...]
Unpacking amd64-microcode (3.20180524.1~ubuntu0.14.04.2+really20130710.1ubuntu1) over (3.20180524.1~ubuntu0.14.04.2+really20130710.1) ...
Unpacking intel-microcode (3.20180425.1~ubuntu0.14.04.2) over (3.20180425.1~ubuntu0.14.04.1) ...
[...]

then:
Calling hook amd64_microcode
amd64-microcode: installing all microcode datafiles for AMD64 processors
amd64-microcode: installing AMD64 processor microcode update support into initramfs...
[...]
Calling hook intel_microcode
intel-microcode: adding microcode for either all or selected Intel processor models
intel-microcode: using early initramfs microcode update mode...

lsinitramfs here also shows microcode for both:
kernel
kernel/x86
kernel/x86/microcode
kernel/x86/microcode/GenuineIntel.bin
[...]
lib/firmware/amd-ucode
lib/firmware/amd-ucode/microcode_amd.bin
lib/firmware/amd-ucode/microcode_amd_fam15h.bin

(note that trusty does not have early microcode loading for amd, only for intel).