Intel Says "No" to 64-bit Pentium 4 in Retail@ 2004/03/26
Earlier this year Intel unveiled its Enhanced Memory 64 Technology also known under 64-bit Extension Technology or IA32e that let Intel’s Prescott, Nocona and Potomac processors to execute specially-written 64-bit code while maintaining absolute compatibility with today’s 32-bit applications. Nocona is code-name for Intel’s upcoming Xeon processors for 2-way servers and workstations launching in Q2 2004; Potomac is the name of the core that enables next-generation Xeon MP chips unveiling in the Q1 2005; Prescott is the core that powers current Pentium 4 E processors and will power special chips for uni-processor servers and workstations with 64-bit capability. Previously it was believed that all Prescott processors in LGA775 packaging, such as Intel Pentium 4 E, would sport EM64T, but Intel denied such claim.
Intel said it would ship Prescott processors with 64-bit capability for 1P applications only to system integrators requesting such microprocessors for their servers and workstations. Although all Prescott CPUs, including Intel Pentium 4 and Celeron, are 64-bit from micro-architectural standpoint, processors supplying for retail channels as well as for typical desktops will have their 64-bit capability disabled.
Intel deems that 64-bit chips should be plugged into widely used desktop and laptop computers only when there is suitable operating system, particularly Microsoft Windows, as well as broad portfolio of drivers for various types of hardware are available. Santa Clara, California-based chip giant believes that users who may decide to install trial version of currently obtainable Microsoft Windows 2003 Server for 64-bit Extended Systems as well as drivers from various companies for this OS may eventually put too much pressure on technical support of PC makers because neither the operating system nor drivers are completely baked to ship to clients.
The archenemy of Intel, Advanced Micro Devices, now ships its Athlon 64 as well as Opteron processor series that also can run specially written 64-bit code and maintain full compatibility with existing software for nearly all market segments. Due to absence of proper 64-bit operating systems personal computer makers usually install 32-bit OS on such machines, as AMD64 processors perfectly execute all available applications.
Intel’s approach to enhance the IA32 architecture is very similar to what AMD implemented into its Opteron and Athlon 64 central processing units. Intel, just like AMD, added a special CPU mode called “64-bit sub-mode”, where 64-bit flat linear addressing, 8 new general-purpose registers (GPRs), 8 new registers for streaming SIMD extensions (SSE, SSE2 and SSE3) and 64-bit-wide GPRs are available along with instruction pointers. Similar to AMD’s 64-bit chips, Intel’s 64-bit extension technology can run in either legacy IA32 mode or IA32e mode. IA-32e mode is the mode a processor uses when running a 64-bit operating system. The IA32e mode consists of two sub-modes: 64-bit mode and compatibility mode, just like it is implemented in AMD64 architecture.
Even though there are some differences between Intel’s and AMD’s 64-bit extended processors’ capabilities, such as NX (non execute) bit featured in AMD64, generally speaking IA32e – now called Extended Memory 64 Technology – and AMD64 – also known as x86-64 – are compatible and are capable of running similar 64-bit code.
The final version of Microsoft Windows for 64-bit Extended Systems will be available sometime in the second half of the year along with some new software that can take advantage of 64-bit processors. The industry expects Microsoft’s new operating system to improve performance of personal computers based on AMD Athlon 64 and AMD Opteron microprocessors that ship today. Additionally, software makers are also likely to follow Microsoft and optimize their products for AMD’s 64-bit microprocessors that are anticipated to be widely available by the end of the year. Given that Intel’s and AMD’s approaches to enhance x86 architecture are generally compatible, Intel’s IA32e chips are also likely to benefit from such optimizations.