Intel seeks quick onboard data route
Are we there yet? The new 820 chip set speeds data across the Pentium III's motherboard
By Michael Cheek
On long road trips along Interstate 95, I often see four lanes of traffic funnel into two and back up cars and trucks for miles. As I watch the crawling parade of brake lights, I think how much it resembles the internal bus structure of a PC motherboard.Ticket to ride
That means the virtual 440BX highways'running at the same old 100 MHz'are choked with data traffic. Now comes 820, Intel's newest chip set, with a posted speed limit of 133 MHz. All the big, fast components will get higher transfer speeds.
And exceeding the speed limit on I-820 is not only tolerated but expected. When work on this virtual beltway is completed, I-820 will provide more and faster lanes for today's and tomorrow's motherboards.
Meanwhile, there's a roadblock. The 820 was supposed to launch on Oct. 25 but was delayed because its memory subsystem experienced glitches. Intel officials have said they expect to release the 820 by year's end, but some PC makers say not until after Jan. 1.
In beltway terms, RAM is a kind of loop around the Pentium III, holding some data in place or sending it in and out of the virtual city within the processor and its cache. But inside the beltway, traffic speeds up instead of slowing down.
The 820 chip set incorporates a new kind of memory and memory subsystem referred to as Rambus. Rambus Inc. of Mountain View, Calif., created its own version of dynamic random access memory (RDRAM), which Intel adopted for the new chip set.
The RAM on the old BX board ran at 100 MHz. On the 820, RDRAM has a special high-occupancy vehicle lane'its own data channel'that lets traffic go up to 800 MHz.
The faster speeds of 700-MHz and 800-MHz RDRAM will cost more.
Inside the beltway, the processor and cache break the speed limit, too. Pentium II and Pentium III processors on the old BX chip set had three 0.25-micron-process chips inside'the processor itself and two Level 2 cache chips.
The newest Pentium III, code-named Coppermine, integrates cache and processor on a single die, made by the 0.18-micron fabrication process Intel recently started using.
The old processor dies without the cache measured 128 millimeters square. The new one with the cache measures only 106 millimeters square. That puts more information in a smaller piece of silicon. Intel officials have said they can make more processors out of a single silicon wafer, so demand will be met rapidly and at a lower price than before.
The old BX processors had a 64-bit data path between cache and processor. Coppermine widens the highway fourfold to 256 bits.
Moreover, the cache used to operate at half the processor's speed. A 400-MHz processor had a 200-MHz cache. But Coppermine's cache and processor run at the same rate. The end result is higher speed for everything, not just the processor.
There's even more information inside this logjam.
Intel has released 10 new processors for desktop PCs but only four of them at new clock speeds: 650 MHz, 667 MHz, 700 MHz and 733 MHz. Some new processors run at the same speed as existing processors. For example, there are now four versions of the 600-MHz Pentium III.Letter perfect
To clear up some confusion, Intel has added letter designations to all processors running from 500 MHz to 600 MHz. The letter B, as in 533B, indicates a new 133-MHz bus. An E following the megahertz rating means the processor was etched by the enhanced 0.18-micron process and integrates Level 2 cache on the die.
A 600EB name indicates a Coppermine processor using a 133-MHz motherboard. Plain old 600 designates a 0.25-micron processor on a 100-MHz motherboard.
At 650 MHz and beyond, it gets a little more confusing. Any rate ending in zero denotes a 100-MHz motherboard; any other number denotes a 133-MHz motherboard. That means the new 667- and 733-MHz chips both use a 133-MHz motherboard; the new 650- and 700-MHz chips have a 100-MHz motherboard.
By the way, the 820 chip set does support a 100-MHz motherboard, although that does not affect inside-the-beltway speeds.
Ever since the 66-MHz Pentium, Intel has built chips with a 66 in the clock rate, but to avoid evil connotations, there will be no 666-MHz processor. Besides, as one Intel official hastened to point out, the rated speed would be 666.6666 followed by sixes into infinity or, rounded up, 667 MHz.
It might not be evil, but it's certainly confusing.
Besides the 820, Intel is adding yet another chip set, the 810E, that can also run at 100 MHz and 133 MHz.
To distinguish the 820 from the 810E, just remember this: The 810E's motherboard integrates the video adapter and borrows from main memory banks to map graphics. The 810E saves the expense of a video card. Performance suffers some, but for basic systems it won't be noticeable.Clear as mud
When you thought it couldn't get more perplexing, Intel also has several new processors for mobile computers. The 440BX chip set will continue to live in notebook computers, but Intel is cranking it up a notch. The mobile 440BX ran at 66 MHz and will now jump to 100 MHz.
On most mainstream or high-end portables, the 1.6-volt Pentium III processors running at 450 MHz and 500 MHz will be standard. Lightweight subnotebooks get the lowest-speed 400-MHz chip at 1.35 volts to save battery life.
Overall, the eye-in-the-sky view of Intel's roadmap looks like downtown streets mixed with thoroughfares, parkways, highways, interstates and one-way alleys. Intel's continued chip specialization certainly creates a megahertz terminology jam, but it's designed to get bits from point A to point B with minimum traffic.
|Intel's chessboard shows confusing strategy for naming processors|
|100-MHz bus and 0.25-micron chip process||500||'||550||600||'||'||'||'|
|133-MHz bus and 0.25-micron chip process||'||533B||'||600B||'||'||'||'|
|100-MHz bus and 0.18-micron chip process||500E||'||550E||600E||650||'||700||'|
for both enhanced
|100-MHz bus and 0.18-micron chip process||'||533EB||'||600EB||'||667||'||733|
|Pentium III processors come in four 600-MHz versions, and each has a different-speed motherboard. If the processor speed ends in zero, the motherboard runs at 100 MHz.|