update t480/3050 errata (tpm and 8254 timer)

Signed-off-by: Leah Rowe <info@minifree.org>

site/docs/install/dell3050.md

@@ -174,3 +174,44 @@ Observe the following photo of the flash (SOIC-8):
 
 You can otherwise flash internally, including from factory firmware(if the
 service jumper is set).
+
+Errata
+======
+
+TPM disabled
+------------
+
+The TPM is disabled on this device, to prevent hanging/boot delay in SeaBIOS,
+due to buggy TPM drivers there.
+
+Legacy 8254 timer
+-----------------
+
+Legacy 8254 timer enabled in coreboot, to prevent SeaBIOS from hanging.
+
+HyperThreading on 3050 Micro
+--------------------------
+
+Also called SMT. This is a feature where you get 2 threads on a single core.
+It can improve performance in some workloads, but is actually a performance
+liability in others, depending on your OS kernel/scheduler and the actual
+workload.
+
+It is a security liability, due to the Spectre/Meltdown attacks, so we
+recommend turning it off, at the very least from your running operating system.
+On *this* platform, you can easily turn it off from coreboot.
+
+**Libreboot disables HyperThreading by default**, from Libreboot 20241206 rev8
+onward, on this board. To turn it back on, please [build from source](../build/)
+and before running the build command, do this:
+
+	./mk -m coreboot t480_vfsp_16mb # replace t480 with t480s if needed
+
+In the menu that appears, go *Chipset -> Enable Hyperthreading* and turn it on.
+Then exit from the menu, saving the config where prompted. You will see this
+menu twice, because there are *two* configs for each of these boards.
+
+SMT is rarely of benefit in practise, but can be useful in some circumstances.
+For example, if you're compiling a large codebase from source that takes hours,
+SMT increases the building speed by about 15 percent; for example, a 3 hour
+build job might take about 2 hours and 40 minutes instead.

site/docs/install/t480.md

@@ -414,6 +414,44 @@ Errata
 Some features either don't work, or are untested, when running Libreboot on
 the ThinkPad T480 or T480s.
 
+TPM disabled
+------------
+
+The TPM is disabled on this device, to prevent hanging/boot delay in SeaBIOS,
+due to buggy TPM drivers there.
+
+Legacy 8254 timer
+-----------------
+
+Legacy 8254 timer enabled in coreboot, to prevent SeaBIOS from hanging.
+
+HyperThreading on T480/T480s
+----------------------
+
+Also called SMT. This is a feature where you get 2 threads on a single core.
+It can improve performance in some workloads, but is actually a performance
+liability in others, depending on your OS kernel/scheduler and the actual
+workload.
+
+It is a security liability, due to the Spectre/Meltdown attacks, so we
+recommend turning it off, at the very least from your running operating system.
+On *this* platform, you can easily turn it off from coreboot.
+
+**Libreboot disables HyperThreading by default**, from Libreboot 20241206 rev8
+onward, on this board. To turn it back on, please [build from source](../build/)
+and before running the build command, do this:
+
+	./mk -m coreboot t480_vfsp_16mb # replace t480 with t480s if needed
+
+In the menu that appears, go *Chipset -> Enable Hyperthreading* and turn it on.
+Then exit from the menu, saving the config where prompted. You will see this
+menu twice, because there are *two* configs for each of these boards.
+
+SMT is rarely of benefit in practise, but can be useful in some circumstances.
+For example, if you're compiling a large codebase from source that takes hours,
+SMT increases the building speed by about 15 percent; for example, a 3 hour
+build job might take about 2 hours and 40 minutes instead.
+
 NFC support in T480
 -------------------