Market Overview - Motherboards: On The Buses
Despite a drop in the number of motherboard manufacturers, there?s still a bewildering choice of products. Roger Gann conducts a guided tour
In Taiwan, the home of motherboard manufacturing, the number of motherboard vendors has fallen from more than 100 three years ago to just 15 active suppliers today. And within a year and a half it has been predicted that there will be fewer than 10 motherboard suppliers in Taiwan. This state of affairs has been brought about largely by Intel?s aggressive entry into the market.
Intel fabs are now producing as much as 80 per cent of all chipsets found on Pentium-class motherboards, leaving the scraps to the half-dozen or so other chipset vendors. While some OEMs still use alternative chipsets, the Var market has largely standardised on Intel. The company has also ramped up motherboard production for those OEM customers seeking a quick entry into the burgeoning Pentium market.
By various estimates, Intel produced eight million to 10 million systems boards in 1995, accounting for about one-third of the systems boards sold worldwide. But since then Intel has relaxed its grip on the motherboard market. It also began licensing its Pentium board designs, enabling vendors to clone its designs with little or no development costs.
With motherboards being such anonymous, almost brand-less, products it is often difficult to know where to start when choosing one.
According to Mark Christou, motherboard product manager at distributor Osmosis Technologies, a good indicator of quality is the length of warranty offered. Osmosis carries high-end Micronics boards and budget-priced Soyo boards in its product lines, and the boards carry two-year warranties, twice that usually offered. Good service and support is another important factor, as are good, clearly written manuals.
One invaluable resource is to be found ? where else? ? on the internet. Tom?s Hardware Guide contains an absolute gold-mine of technical info, plus hints and tips about PC hardware, and is well worth a visit. There you?ll find various motherboard top tens and best buy recommendations. For example, for 430HX boards, Tom Pabst recommends the Asus P/I-P55T2P4 and Abit IT5H boards and for Triton 430VX boards, the Abit IT5V. It?s also worth searching Yahoo on the keyword ?motherboards? ? you?ll find all the motherboard manufacturers that have an internet presence.
All current Pentium motherboards ship with Socket 7 zero insertion force (Zif) sockets, which make it easy to insert and extract CPUs. Until recently, the only CPU that would fit a Socket 7 had an Intel badge. Today the story is very different and offerings from Cyrix and AMD can be added to the CPU shortlist.
A current motherboard will typically take Intel Pentiums with speeds running from 75MHz to 200MHz, Cyrix 6x86s from the P133+ to the P200+ and AMD K6 processors up to 266MHz. These processors use a variety of voltages, from 5V downwards, and the latest boards will automatically detect the correct voltage to apply to the processor.
If the CPU is the brain of the PC, then the chipset is the nervous system: it controls the memory I/O, the bus I/O, serial and parallel ports and the integrated IDE hard disk controllers. Chipsets also handle interrupt requests (IRQs) and direct memory accesses (DMAs).
There is a wide variety of chipsets available ? OPTi Viper or VIA Apollo-VP ? but those bearing the Intel logo are the most popular. Most current motherboards now ship with either the 430HX or 430VX chipsets (formerly the Triton II). The former is aimed at the corporate PC, while the VX chipset is meant for home and small-business PCs. Each offers a 64bit memory path, concurrent PCI and the 82371SB PCI I/O IDE Xcelerator. This chip supports the universal serial bus (USB), as well as PIO (programmed input/output) and bus-mastering IDE and it is PCI 2.1-compliant.
The HX chip set also supports up to 512Mb of main memory (EDO or DRam), dual processors and ECC memory. The VX chipset differs from the HX in that it supports up to only 128Mb of main memory but also supports synchronous DRam (SDRam).
In February, Intel released the successor to the HX and VX, the 430TX chipset, which comprises the 82371AB and 84239TX chips. Motherboards are now starting to appear with these chipsets.
As well as incorporating all the features of the HX/VX, the TX includes support for DMA/33, a Quantum-developed EIDE standard that permits burst data transfer rates of up to 33Mbps, effectively double that available with Mode 4 PIO drives.
Not only is it faster, but the new protocol also includes CRC error checking for the first time. The TX is also optimised for Pentium MMX CPUs, permits mix and match of EDO and SDRam Simms and also supports a new power management regime ? Intel?s Dynamic Power Management Architecture ? which is ACPI compatible, plus new management facilities through the system management bus.
The Bios (basic input/output system) is a chunk of code that typically resides on a Rom chip on the motherboard. It is essential to the operation of the PC. It runs a power-on self-test (Post) when a PC is first turned on ? it checks the memory, DMA and interrupt controller and other key components, and then loads the operating system from disk and controls keystroke interpretation and port communication.
Although there are many different Bios vendors, including Phoenix, Award, AMI and Microid Research, the differences between their products aren?t great.
However, there are several things to look out for. You should definitely look for a Bios that supports plug-and-play and power management. Plug-and-play is desirable, though not required, if you plan to use Windows 95. Without a plug-and-play Bios, your system is not fully plug-and-play compliant, and features such as power management and add-in card auto-detect may not work.
If your company buys computers with Energy Star certification, the Bios must have support for power management. The Bios should support both system and monitor suspend and sleep modes.
Another important feature is Flash Rom. This permits the easy upgrading of the Bios firmware from a floppy disk, rather than by physically extracting the old Roms and replacing them with updated ones. For example, most Intel motherboards feature Bioses that are held in Flash Rom, and it?s easy to download the latest Bios firmware from the Intel Web site.
Software configurable ? or jumperless ? motherboards have recently started to appear. Most current motherboards need to be configured before they can be installed properly, and this typically involves moving a number of tiny jumpers on the motherboard, especially when it comes to specifying the type of CPU you?re installing.
Needless to say this is a fiddly job and it?s too easy to get it wrong. The latest motherboards feature soft menu Bioses that let you change things like the bus speed, system clock and CPU multiplier from the comfort of your keyboard.
A motherboard will have several buses: the memory bus, cache bus, ISA bus and PCI bus. Although today?s Pentiums run at clock speeds of 75 to 200MHz, the memory and cache are limited to 50, 60, or 66MHz.
The memory subsystem?s running speed is called the motherboard speed, and the processor is clock-multiplied to run from one-and-a-half to three times as fast. Some rival processors, such as the Cyrix 6x86, support faster motherboard speeds ? 75Mhz and 83Mhz ? and this, of course, permits faster CPU operation
The yawning gap between CPU and memory subsystem speeds creates a bottleneck, especially at high CPU speeds. To help alleviate the problem, the motherboard speed must be increased to 75MHz and beyond. It?s not an easy task; above 75MHz, electromagnetic interference (EMI) becomes a significant problem.
The 10 per cent speed difference between a 66MHz and a 60MHz bus may seem trivial, but there is a cascade effect. Because the PCI bus is a straight divisor of the motherboard clock, the differences between CPU speeds are greater than they appear at first glance. So although it may appear that a 120MHz PC should be only slightly slower than a 133MHz unit, in reality the combination of slower CPU, memory subsystem and PCI bus (60 vs 66MHz) makes a Pentium 120 barely faster than a Pentium 100.
The universal serial bus (USB) is a new bus which is designed to provide a single interface to connect mice, joysticks, keyboards and telecommunications devices. USB?s powered hub operates at 12Mbps for devices such as printers that need their own power supplies, while a secondary, low-speed channel runs at 1.5Mbps for mice and keyboards.
The USB standard allows up to 127 devices to be daisy-chained, similar to the way the Macintosh is set up today, and comes as a blessed relief for PC users that have all four Com ports spoken for and want to add yet another peripheral. Eventually, monitors may feature USB hubs in their tilt and swivel stands and the mouse, keyboard, modem, scanner and joystick will be plugged in here rather than at the rear of the PC.
Takeup of the USB has been surprisingly slow. Although PCs sporting USB sockets first materialised last summer, there has been a conspicuous absence of USB peripheral components.
The software side has been equally lamentable. Windows 95 drivers for USB have only just appeared and they?re included in the OSR2 release of Windows 95. Many modern motherboards now have connectors for USB ports, but the actual sockets are seldom included with them.
Similarly, many motherboards have IrDA infra-red connectors, but as yet no motherboards have shipped with an infra-red transceiver/sensor.
All motherboards will have expansion slots to take expansion cards, of course. Once upon a time, the original IBM PC, circa 1981, had 8bit ISA (industry standard architecture) slots. These were extended to 16bit with the launch of the IBM AT in 1984.
The slow, 8MHz speed of the ISA bus made it inevitable that, as processor speeds rocketed, faster options would appear. For instance, 486 PCs sported VL-Bus extensions with a faster 33MHz bus speed and hence greater throughput. VL-Bus, however, was rapidly superseded by Intel?s peripheral component interconnect (PCI) standard, which although no faster, did offer throughputs as high as 132Mbps.
Most current Pentium motherboards offer a mixture of expansion slots, perhaps three ISA and four PCI slots as a minimum, although better boards might offer an extra slot of each type. Note that owing to the opposite handing of ISA and PCI cards, you always lose a slot. This is because one slot will be an either/or slot.
Extended data out Ram is a fairly recent memory technology and provides a speed gain of up to 10 per cent in the memory subsystem. EDO Ram provides a wider effective bandwidth by offloading memory pre-charging to separate circuits. As a result it offers a 10 per cent speed boost over DRam, while Burst EDO Ram offers another 10 to 20 per cent.
Fast-page memory, by contrast, has to wait between these charging cycles, thus causing delays. EDO hasn?t been around long, but despite its popularity it is already being ousted by SDRam. To use EDO Ram, both the Bios and the chipset of a PC must explicitly support it.
Compared with EDO DRam, synchronous DRam is capable of transmitting data on every clock cycle, conferring a peak system performance improvement of about 10 per cent over EDO. SDRam is a solution for fast (sub-66MHz) motherboard designs ? the same clock drives both CPU and Ram. It
offers four times the throughput of conventional DRam and is easier to run at speeds as fast as 80MHz.
Level 2 cache is often soldered directly on to the motherboard and can?t be upgraded ? you typically get 256Kb of pipeline burst-mode static Ram. However, some of the better motherboards support Coast (cache on a stick) modules, which plug into special, PCI-like sockets close to the CPU itself.
All Pentium motherboards come equipped with at least four 72-pin Simm slots. Seventy-two-pin Simms are 32bit devices, and because the Pentium has a 64bit data path they have to be fitted in pairs. State-of-the-art motherboards can take 64Mb Simms and so have a maximum capacity of 4x64Mb or 256Mb.
Just recently 64bit dual in-line memory modules (Dimms) have started to appear. Dimms have 168 pins in dual rows of contacts, one on each side of the card. With the additional pins, a computer can retrieve information from Dimms 64 bits at a time instead of the 32bit or 16bit transfers usual with Simms.
Dimms are a bit longer and a bit taller than Simms and they are fitted vertically into their sockets, with a couple of clamps at either end. PCs typically have just one or two Dimm slots. Because Dimms are 64bit devices they can be fitted singly. Dimms also tend to use SDRam exclusively.
All motherboards, except those in the original IBM PC, use a slot spacing of 0.8 inches. The slots are always located in the left rear corner of the motherboard. What distinguishes
the popular Baby AT form factor from other motherboards is largely the mounting holes it uses and its maximum size of 8.5in wide by 13.5in deep.
You can still buy systems with the larger AT motherboard form factor which measures as large as 12in wide by 13.5in deep, and uses different mounting holes.
The Baby AT design, however, won predominance over the AT design for several reasons. Among them are that most systems didn?t need the extra space as chip size was reduced, smaller boards are less expensive to manufacture and such boards allow the use of a smaller system chassis.
But the Intel ATX motherboard specification should eventually displace the long-used Baby AT design.
ATX? more efficient use of space and cheaper four-layer design is good news for systems integrators. ATX and Baby AT boards are approximately the same size, but the ATX board is rotated 90 degrees within the PC?s case, allowing easier access to internal components. The I/O slots still run parallel to the side panels and exit at the left rear corner of the system, but unlike the Baby AT and larger AT motherboards, an ATX motherboard is wider than it is deep.
This offers several benefits, most of which relate to moving the processor, Simm slots and other components to the right of the expansion slots. One main advantage is that you should no longer find that a PC?s I/O slots can?t accept full-length cards just because a Simm, a processor fan or heat sink interferes with its installation. The likelihood that you?ll have to remove one or more expansion cards to access the CPU, Simm slots or other motherboard components also decreases thanks to this layout.
Another advantage is that the CPU is positioned closer to the power supply and its cooling fan, which lie to the right of the expansion slots. This should eliminate the need for dedicated processor fans in many systems, according to Intel. In turn, this placement should lower system cost and power consumption, not to mention making CPU upgrades easier.
This new orientation reduces clutter inside the chassis, making it much easier to access the the interior of a PC.
It also lets motherboard vendors load more components and connectors on to the motherboard itself, rather than cabling components to a connector mounted in the chassis.
And from an electrical point of view, shorter ribbon cables mean there is less electrical interference and signal loss, with the result that today?s faster interfaces can perform more reliably.
ATX also helps eliminate internal tangles by letting motherboard ribbon-cable connectors for floppy and hard drives be placed where they belong ? near the drive bays.
Still another benefit is that a web of ribbon cables will no longer occupy a large space inside a PC?s chassis, thereby allowing the system to be cooled more adequately. On the downside, ATX?s four-layer design isn?t likely to support bus speeds above 66MHz.
Intel and Microsoft have already teamed up to give the industry a glimpse of the future of motherboards as they see it. Their PC 98 roadmap includes a number of interesting points, including the end of the ISA bus and an insistence on motherboards being network-ready and video conference-ready. Bus speeds will almost certainly have to increase, especially now that Intel is producing chips that run at 266MHz.
If it wants to hang on to the tight grip it has on the industry, given its 80 per cent share of the chipset market, Intel is going to have to wise up to the work being done by its competitors (particularly Cyrix) and cater for higher speeds.