uctions, and speeded-up segment-register writes, which allow the PII to run older, 16-bit software faster than the Pentium Pro.
New Architecture
First, the PII represents a whole new architecture that carries a much greater possibility for future expansion than do its Pentium predecessors that use Socket 7/8 (the zero insertion force [ZIF]-type socket where the processor sits). For example, the Pentium's limited upgradability is due to the lack of on-chip circuitry and other chip components that are necessary for you to be able to upgrade to a faster CPU.
The PII's Single Edge Contact (SEC) cartridge, which is about the size of a Nintendo cartridge, sits in Slot 1 on the motherboard and is designed to make upgrades easy. The tool-free SEC cartridge pops out from Slot 1 after you unscrew the re
tainer, heat sink, and CPU fan.
With the PII design, gone are the days when you had to pry out the processor with a rake and risk bending pins while changing chips. Within the SEC cartridge is a circuit board that contains the processor, some core logic, and system and bus caches -- all the components needed to handle future high-frequency versions of the PII (although SRAM chips for the L2 cache are not in the same package as the CPU die).
Dual-Bus Support
Like the Pentium Pro, the PII uses the Dual Independent Bus (DIB) architecture. This accelerates the flow of information within the system, boosting overall performance to three times than of a single-bus-architecture processor. The DIB architecture allows today's 66-MHz system-memory bus to move to higher speeds in the future.
Two buses make up the DIB: the L2 cache bus and the processor-to-main-memory system bus. The PII processor can use both buses simultaneously, which increases the chances that it will achieve its peak exec
ution time of three instructions per clock cycle.
MMX Technology
Like the Pentium with MMX, the PII processor includes accelerated MMX, which enables it to execute two MMX instructions at a time. Added to the PII are 57 new MMX instructions specifically designed to process video, audio, and graphical data more efficiently. The use of single instruction/multiple data (SIMD) technology enables one instruction to perform identically on multiple pieces of data and allows the chip to reduce the compute-intensive loops common with video, audio, graphics, and animation.
Intel expects MMX to play a significant role in videoconferencing, among other applications. It also expects upcoming MMX drivers to improve printing.
Setting the Specs
Future possibilities aside, the current emphasis of PCs with the PII processor and the 440FX (Intel's new PII chip set) is performance. In
this roundup
we focus on a range of systems, from high-powered 266-MHz PCs to surprising
ly competitive 233-MHz machines.
Although the PII market extends beyond mainstream business, we chose to focus on Windows NT PCs ranging in price from about $2200 to $4100. Each was equipped with a single-processor configuration and 64 MB of RAM. A maximum 512 KB of secondary processor cache, a 32-KB L1 cache (16 KB for instructions, 16 KB for data), and a minimum 3.8-GB hard drive were also included. In addition, a CD-ROM drive, a 3-1/2-inch floppy drive, and VGA with 4 MB of video memory were part of the system specifications.
The PII is optimized for 32-bit code. As BYTE readers increasingly demand coverage that reflects what they most often use, we selected Windows NT Workstation 4.0 as our OS for this roundup.
What's Next?
Expected to ship this month, Intel's 440LX chip set will include add-ons to better exploit the PII's abilities. The 440LX will be compatible with the Advanced Graphics Port (AGP), which gives graphics chips dedicated access to main memory. Error-correction-co
de (ECC) RAM will also be supported, making the PII with the 440LX chip set ideal for high-end desktops and servers. The 440LX will include support for synchronous DRAM (SDRAM), which can boost overall system performance by allocating memory for each bit of data that passes through the PCI bus. You can also expect to see Ultra DMA hard disk support.
The current iteration of the PII with the 440FX chip set supports two-processor symmetric multiprocessing (SMP). Support for four-way SMP won't be available until 1998. In addition, the internal bus speed is 66 MHz; support for a 100-MHz bus is not expected until 1998.
By the time you read this, 440FX PIIs are expected to plunge in price as the first PIIs with the 440LX chip set roll out, so seek current pricing when making your buying decisions. Pricing aside, the PII's high-performance test results and expandability make the jump to Intel's new platform worth the while of many business and home users looking for entry-level PCs.
Contributors
Michelle Campanale
, technical editor/BYTE
Andrew Froning
, managing editor/NSTL
Dorothy Hudson
, project manager/NSTL
Linda Higgins
, editorial associate/BYTE
Maggi Bender
,
John McLoughlin
, and
John McDonough
, product testers/NSTL
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Power Platforms: 233- and 266-MHz Pentium IIs Compared
