switch (c->x86_vendor) {
case X86_VENDOR_INTEL:
- if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
+ /*
+ * There is a known erratum on Pentium III and Core Solo
+ * and Core Duo CPUs.
+ * " Page with PAT set to WC while associated MTRR is UC
+ * may consolidate to UC "
+ * Because of this erratum, it is better to stick with
+ * setting WC in MTRR rather than using PAT on these CPUs.
+ *
+ * Enable PAT WC only on P4, Core 2 or later CPUs.
+ */
+ if (c->x86 > 0x6 || (c->x86 == 6 && c->x86_model >= 15))
return;
- break;
+
+ pat_disable("PAT WC disabled due to known CPU erratum.");
+ return;
+
case X86_VENDOR_AMD:
case X86_VENDOR_CENTAUR:
case X86_VENDOR_TRANSMETA: