Intel had tried unsuccessfully to push Apple to migrate the Macintosh platform to Intel chips. Apple concluded that Intel's CISC (Complex Instruction Set Computer) architecture ultimately would not be able to compete against RISC (Reduced Instruction Set Computer) processors. While the Motorola 68040 offered the same features as the Intel 80486 and could on a clock-for-clock basis significantly outperform the Intel chip, the 486 had the ability to be clocked significantly faster without suffering from overheating problems, especially the clock-doubled i486DX2 which ran the CPU logic at twice the external bus speed, giving such equipped IBM compatible systems a significant performance lead over their Macintosh equivalents. Apple's product design and engineering didn't help matters as they restricted the use of the '040 to their expensive Quadras for a time while the 486 was readily available to OEMs as well as enthusiasts who put together their own machines. In late 1991, as the higher-end Macintosh desktop lineup transitioned to the '040, Apple was unable to offer the '040 in their top-of-the-line PowerBooks until early 1994 with the PowerBook 500 series, several years after the first 486-powered IBM compatible laptops hit the market which cost Apple considerable sales. In 1993 Intel rolled out the Pentium processors as the successor to the 486, while the Motorola 68050 was never released, leaving the Macintosh platform a generation behind IBM compatibles in the latest CPU technology. In 1994, Apple abandoned Motorola CPUs for the RISC PowerPC architecture developed by the AIM alliance of Apple Computer, IBM, and Motorola. The Power Macintosh line, the first to use the new chips, proved to be highly successful, with over a million PowerPC units sold in nine months. However, in the long run, spurning Intel for the PowerPC was a mistake as the commoditization of Intel-architecture chips meant Apple couldn't compete on price against "the Dells of the world".