The 6x86 and 6x86L weren't completely compatible with the Intel P5 Pentium instruction set and is not multi-processor capable. For this reason, the chip identified itself as a 80486 and disabled the CPUID instruction by default. CPUID support could be enabled by first enabling extended CCR registers then setting bit 7 in CCR4. The lack of full P5 Pentium compatibility caused problems with some applications because programmers had begun to use P5 Pentium-specific instructions. Some companies released patches for their products to make them function on the 6x86.