Figure 355 in Software

Printer PDF-417 2d barcode in Software Figure 355

Intel Pentium III Xeon (photo courtesy of Intel Corp)

Intel Pentium 4 Xeon (photo courtesy of Intel Corp)

Both AMD and Intel currently produce the newest thing in microprocessing: 64-bit CPUs A 64-bit CPU has general-purpose, floating point, and address registers that are 64 bits wide, meaning they can handle 64-bit-wide code in one pass twice as wide as a 32-bit processor And, they can address much, much more memory With the 32-bit address bus of the Pentium and later CPUs, the maximum amount of memory the CPU can address is 232, or 4,294,967,296 bytes 64 With a 64-bit address bus, CPUs can address 2 bytes of memory, or more precisely, 18,446,744,073,709,551,616 bytes of memory that s a lot of RAM! This number is so big that gigabytes and terabytes are no longer convenient, so we now go to an exabyte (260) A 64-bit address bus can address 16 exabytes of RAM No 64-bit CPU uses an actual 64-bit address bus Right now, the most RAM anybody uses is 4 GB, so there s not much motivation for creating a CPU or a motherboard that can handle and hold 16 EB Every 64-bit processor gets its address bus clipped down to something reasonable The Intel Itanium, for example, only has a 44-bit address bus for a maximum address space of 244, or 17,592,186,044,416 bytes Initially, both AMD and Intel raced ahead with competing 64-bit processors Interestingly, they took very different paths Let s look at the two CPUs that made the first wave of 64-bit processing: the Intel Itanium and the AMD Opteron

Intel Itanium (Original and Itanium 2)

Intel made the first strike into the 64-bit world for PCs with the Itanium CPU The Itanium was more of a proof of concept product than one that was going to make Intel any money, but it paved the way for subsequent 64-bit processors The Itanium had a unique 418-pin pin array cartridge (PAC) to help house its 2- or 4-MB Level 3 cache (Figure 357)

Mike Meyers CompTIA A+ Guide: Essentials (Exam 220-601)

Intel Itanium (image courtesy of Intel Corp)

The Intel Itanium 2 was Intel s first serious foray into the 64-bit world To describe the Itanium 2 simply in terms of bus sizes and clock speeds is unfair The power of this processor goes far deeper Massive pipelines, high speed caching, and literally hundreds of other improvements make the Itanium 2 a powerful CPU for high-end PCs The Itanium 2 uses a unique form of PGA that Intel calls organic land grid array (OLGA) See Figure 358 Intel Itanium 2

Physical address: 50 bits Frontside bus width: 128 bit External speed range: 100 MHz (quad-pumped)

Intel Itanium 2 (image courtesy of Intel Corp)

Internal speed range: 900 MHz, 1 GHz Watts: 90 100 Multiplier range: 9 10 L1 cache: 32 KB L2 cache: 256 KB L3 cache: 15 MB, 3 MB Package: OLGA Socket(s) used: Socket 611

Intel made a bold move with the Itanium and the Itanium 2 by not making them backward compatible to 32-bit programming In other words, every OS, every application, and every driver of every device has to be rewritten to work on the Itanium and Itanium 2 In theory, developers would create excellent new applications and devices that dump all the old stuff (and problems) and thus would be more efficient and streamlined If a company has a lot invested in 32-bit applications and can t make the jump to 64-bit, Intel continues to offer the Pentium 4 or Pentium Xeon If you need 64-bit, get an Itanium 2 AMD didn t agree with Intel and made 64-bit processors that also ran 32-bit when needed Intel would eventually follow AMD in this decision