Intel Merced vs. Alpha 21264

Introduction

Intel's plans for the next millenium are quite concrete. Merced is going to be Intel's first 64 Bit processor based on the new IA-64 architecture. And Intel has a powerful ally: Hewlett Packard is the co-developer of this new architecture and has already begun to change over from PA-RISC to IA-64. This means that their classic RISC line should be abandoned within the next two or three years.

But Intel's efforts to reach for the top have brought basic changes into the market: Others have to make their decisions for the future as well. Silicon Graphics is going to change over to Intel and has stopped the R14000 project, Windows NT will be the future base and IRIX will also be adapted to IA-64. Sun Microsystems is the next who is planning the future with IA-64. Apple, the number one seller of IBM/Motorola's Power PC architecture, has been steadily loosing shares in the RISC market in the last time. IBM is still having two RISC lines (PPC and RS6000 respectively AS/400) and plans to fuse them together with the 64 Bits successor called Power3 which is expected to come still this year (starting with 300 MHz).

The only RISC architecture that will really have importance in the next years will be Digital's Alpha. Intel's IA-64 plans have started to split the market and it seems like this in going to be a fight for the future of RISC. Intel is confident that IA-64 is powerful enough to dominate the market, especially with such a vast support from all sides.

But the introduction of Merced (planned for mid-2000) could become unsuccessful and somehow embarrassing. Digital already published the estimated performance of the 21264: It will reach 1000 MHz (1 GHz) around the year 2000 with approximately 100 SPECint95 and about 150 SPECfp95. The first version of Merced is only expected to achieve 40 or 50 SPECint95 and 75 SPECfp95. The second generation of IA-64 CPUs could improve the performance independently from the clock speed, since Intel and HP will require some more time to get to the bottom of the potential IA-64 is expected to have.

But the future for Digital's Alpha is not that bad. Compaq, known as Intel's best customer, is now officially planning to sell servers based on Alpha CPUs. If Compaq can continue this new course they should be able to spoil Merced's debut with better performing products.

The 21264 has some interesting new features that revalue the Alpha's basically simple RISC architecture. The L1 cache has been increased (64+64 kB data and instruction cache) and is able to read up to four instructions per cycle. Some additional function units, a very precise branch prediction, new instructions enhancing its video capabilities and a very high bus performance (thanks to double data rate Cache-RAM at 128 Bits and the Tsunami chipset addressing main memory with 256 Bits) complete the CPU. But for the first time an Alpha RISC processor features out-of-order execution as well: The CPU is now able to reorganize the sequence of orders to effectively use all available pipelines and minimize waits.

The next important advantage for the 21264 is the advanced bus protocol. Intel's GTL+ supports 64 Bits and today 100 MHz. Digital's protocol will work at 333 MHz and is exactly the same base as AMD will use with the K7. The code name is EV-6 and AMD has already developed a new CPU interface using the single edge connect we all know from Slot-1, just calling it Slot-A. If Digital gets the chance to produce their 21264 CPU in for Slot-A, it would be no problem for us to get a Slot-A motherboard and either use an Alpha or a K7 CPU - all you would need is the right BIOS!

The Alpha 21264 is going to fulfil the synthesis between high performance thanks to its special features and complexity, and even more performance thanks to very high clock speeds. The architecture can be called highly optimized and IA-64 is likely to fail its hunt for the very top, since there are still no Merced silicon prototypes available. No doubt, Intel will certainly conquer the market once again, but if the Alpha survives, Intel will not be that fast within the next years and the performance crown will still be held by Digital.