Taking steps toward 64-bit processing

Upgrading to the latest generation of hardware doesn't mean you have to abandon today's applications

A growing number of volume systems on the market today are incorporating the new 64-bit architectures from AMD and Intel. When you buy new hardware, you’re part of the 64-bit revolution almost by default. But you still have a choice to make: Should you flip on those extra 32 bits by running 64-bit versions of your operating systems and applications?

Benchmarks can reveal part of the picture. Pay attention not just to the results but to the system configurations vendors used to run their tests. SPEC (Standard Performance Evaluation Corporation) ranks among our favorite synthetic benchmarks. We used SPEC’s query engine to pull up the best results among AMD’s tests of Opteron CPUs and found something that may surprise you: Some of AMD’s brag-worthy results come from benchmarks run on stock systems loaded with 32-bit Windows.

Why? Because, in addition to 64-bit processing, the new crop of x86 systems brings additional benefits, including dual-core processors, faster buses, and more room in each system for memory. Except in rare circumstances, you’ll experience a more noticeable performance increase from doubling up on cores than from adding a second dual-processor server to a cluster. Likewise, AMD’s AMD64 and Intel’s EM64T architectures up the speed limit on pathways between CPUs and system memory. The resulting increase in RAM access speed is felt across all application types, without special tuning or architecture-specific software upgrades.

The only real caveat is that wiping out performance bottlenecks could expose I/O bottlenecks. For example, the slower x86 servers you’re running now may already perform calculations and access memory fast enough to keep their Ethernet or Fibre Channel interfaces running at top speed. Increasing the number of cores and the speed of RAM will raise the stress on those existing peripherals. If they have no headroom to spare, you won’t see improvements in a switch to 64-bit x86 systems because the CPUs will waste time waiting for peripherals to respond to requests.

Beyond the ancillary benefits of new x86 architectures, the biggest gains will come when you switch to true 64-bit software, both OSes and applications. Unfortunately, there’s no right course here. Understanding the effort and benefits of going pure 64-bit requires discussions with your software and peripheral suppliers, just as if you were switching from x86 to Sparc or another platform. Costly upgrade license fees may be enough to convince you to wait. The good news is that 64-bit systems perform well enough on older code that you shouldn’t feel pressured to leave 32 bits behind just because you see 64 bits everywhere you look.

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