The Alpha 21264: NT's Greatest RISC
Windows NT Magazine / December 1998
The Alpha 21264: NT's Greatest RISC
Tom R. Halfhill
[Editor's note: This<br>article was originally scheduled for publication in the<br>September 1998 issue of BYTE Magazine but was canceled when BYTE folded in<br>June 1998. It appeared instead in Windows NT Magazine<br>and in C'T, a<br>German computer magazine. This text is<br>the original English version.]
While the world waits for Intel's 64-bit Merced chip and<br>Microsoft's 64-bit version of Windows NT, Digital<br>Equipment is offering a sneak preview of the next<br>generation in NT processing. The Alpha 21264 is a 64-bit<br>processor that runs NT. It's one of the fastest chips in<br>the world. And it's available today.
The 21264 is the latest generation of the Alpha<br>microprocessor architecture. Digital expects the 21264 to<br>reach clock speeds of more than 700MHz this year, so this<br>processor upholds the speed demon reputation that the<br>21164 and 21064 established for Alpha chips.
Alpha is the last RISC architecture for which Microsoft is<br>developing future versions of NT. Microsoft is phasing out<br>NT for MIPS Rx000 chips, and the PowerPC NT never really<br>got off the ground. The only other CPU architecture that<br>runs NT is, of course, Intel x86. Despite Intel's market<br>dominance, the Alpha has one big advantage over the x86:<br>increased performance, especially performance of<br>floating-point tasks. Alpha systems generally cost more<br>than their Intel counterparts, but Alpha systems are<br>faster, and they excel at math-intensive engineering and<br>scientific applications.
To move beyond the performance limitations of the<br>20-year-old x86, Intel partnered with HP in 1994 to<br>develop a new CPU architecture: Intel Architecture-64<br>(IA-64). Intel expects systems that use the Merced<br>processor, the first processor to implement IA-64, to ship<br>in mid-2000. But the Merced might not be the fastest chip<br>on the NT market in 2000. Digital says that by the time<br>Merced appears, the 21264 will be running at a clock<br>frequency of 1000MHz (1 gigahertz [GHz]). At that speed,<br>the 21264 will be substantially faster than the Merced<br>according to estimated CPU benchmarks. (For a review of<br>21264 speeds, see Figure 1.)
Digital said the first 21264 systems would hit the streets<br>in late 1998, so you don't have to wait two years for<br>64-bit performance. However, the 21264 won't reach its<br>potential until Microsoft ships a 64-bit version of NT for<br>both IA-64 and Alpha chips. (Microsoft hopes to ship the<br>64-bit NT in 2000.)
Whither RISC?
The race between the 21264 and IA-64 processors is not<br>just a subject of idle gossip. At stake is nothing less<br>than the future of RISC for NT and every other operating<br>system (OS).
Outside of the highly specialized embedded-application<br>market, RISC is in retreat. Currently, the most popular<br>RISC architecture for the desktop is the PowerPC chip,<br>which IBM and Motorola produce jointly. But the largest<br>customer for desktop PowerPC chips is Apple, and the<br>Macintosh has only about 4 percent of the PC market share<br>according to International Data Corporation (IDC). In<br>June, IBM and Motorola announced that they are dissolving<br>their 7-year PowerPC partnership and will develop future<br>PowerPC chips separately.
IBM's other RISC architecture, the Power series, is<br>merging with the PowerPC. IBM is phasing out the Power<br>chip as a distinct architecture. The new 64-bit Power3<br>chip is the first processor that unifies Power and PowerPC<br>technologies.
Battling recent losses, Silicon Graphics is moving away<br>from its MIPS Rx000-series RISC processors. Silicon<br>Graphics canceled its next-generation Rx000 projects and<br>recently spun off the embedded-chip portion of MIPS<br>Technologies as a separate company. Silicon Graphics is<br>developing x86-based systems for NT and porting IRIX to<br>IA-64.
Sun Microsystems is porting Solaris to IA-64. That move<br>has prompted some industry analysts to speculate that the<br>new UltraSPARC-III will be the last major generation of<br>the SPARC family, although Sun claims that the rumors are<br>false.
HP is porting HP-UX to IA-64 as part of its strategy to<br>move away from Precision Architecture-RISC. PA-RISC will<br>gradually exit the market after IA-64 debuts. IA-64 will<br>be backward compatible with PA-RISC.
The Alpha is the fastest RISC chip according to most CPU<br>benchmarks and the only NT alternative to the x86. But the<br>Alpha's future isn't certain because of recent shakeups at<br>Digital. The company sold its chip foundry in Hudson,<br>Massachusetts, to Intel. Despite some misleading news<br>reports, Digital sold only the foundry, not the Alpha.<br>Digital will continue to independently design Alpha<br>processors but will farm out the chips' manufacturing to<br>Intel and other licensees. The two current<br>Alpha-manufacturing licensees are Samsung and Mitsubishi.<br>Digital is also negotiating deals with AMD and IBM<br>Microelectronics. Mitsubishi currently has no plans to<br>manufacture the 21264, although the company continues to<br>provide technical support...