Diamond Micronics C400 motherboard

Review date: 1 December 1998
Last modified 03-Dec-2011.


Diamond Multimedia got into motherboards the Microsoft way - they found someone who made good ones, and bought them. Micronics is now part of the Diamond empire, and the C400 is the first motherboard to carry the Diamond name.

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Yup, that's a motherboard. Note the comprehensive data sheet that supplants a full paper manual.

The C400 is a mini-ATX BX chipset board with four PCI slots, one ISA slot and one slot shared between PCI and ISA. There's also one AGP video slot. The C400 accepts any Slot 1 CPU (Pentium II or Celeron) up to 450MHz, supports up to 768Mb of RAM in its three DIMM slots, and has the usual serial, parallel and twin USB ports, dual Ultra DMA/33 EIDE connectors and an Award 1Mb flash-upgradable BIOS.

It's also got all the usual extras that don't often get used - an IrDA header, Wake On Ring and Wake On LAN support, and an SB-LINK header for users of older PCI Sound Blasters.

Unusually, this motherboard doesn't come with a comprehensive paper manual. A surprisingly complete Quick Installation Guide sheet gives enough information for even inexperienced users to set the board up, but the full documentation is on the almost-empty accompanying CD. You might think this would present a problem for those who don't already have a PC to read the manual on, but, as I said, the simple data sheet is actually very good. If you can't figure out what to do from the Quick Installation Guide, the manual probably isn't going to help you.

One point that the Quick Installation Guide doesn't make clear is how to mount the CPU retention doohickey - the rails that the Slot 1 processor slides down into. The Quick Installation Guide shows one kind of fastener for the rails, the CD-ROM manual shows another, and what's provided is yet a third, a cheapo system where you push nylon pins down into the base of the rails to lock the retainer in place. This sort of retainer works fine if it's installed properly, but if the pin receiving locking post things in the rail base aren't pushed all the way down to start with, you can burst a blood vessel pushing on the fasteners and still end up with a dodgily mounted CPU.

This aside, the C400 docs are superb. They explain more than most manuals,  including detailed BIOS setup information, and are written in clear English, and properly proofread. It's a shame that this is an unusual feature.


This is a well laid out, well labelled motherboard.

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The slightly awkward CPU retention kit is only a minor problem.

The switch and LED connectors are in one simple line, not the one-and-a-half two-column blocks with ultra-teeny labelling that many manufacturers inflict on us. Indeed, everything's labelled in text of a size visible to most humans.

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Clearly labelled LED and switch connectors, all in one row in one place. Where have you been all my life?

The C400 also seems to be well thought out electronically. It has large smoothing capacitors, keyed connectors and solid soldering on the stress-bearing ports. Corner-cutting in the electronics causes crashes, which should not be a problem here.


Forget it. This is not a speed freak redline-your-CPU board. You can't set processors to bus speeds other than those they're supposed to run at, and you can't change processor voltage. Well, not without using nail polish or Teflon tape or an X-Acto knife. You don't want to know. Trust me.


All BX chipset motherboards are almost exactly the same speed, so the only performance feature that matters is reliability. Judging by its construction quality, the C400 should be a highly reliable piece of equipment.


If you've never built your own PC before, this is a great board to choose, simply because of its clear labelling and good documentation. And you don't sacrifice speed, either, provided you don't want to overclock your processor. At less than $250 (Australian dollars) it's a great motherboard at a good price.




  • Easy to set up
  • Well made
  • Excellent documentation
  • Useless for overclocking
  • No proper paper manual


AGP: The Accelerated Graphics Port is based on the PCI standard, but clocked at least twice as fast to accommodate the demands of 3D graphics. AGP lets the graphics board rapidly access main memory for texture storage.

ATX: Intel's ATX motherboard specification improved on the old AT spec by rotating the whole arrangement 90 degrees in the case, and moving the CPU and RAM away from the expansion slots so long cards wouldn't foul them. ATX also supports a smarter power supply, which can turn on and off in response to port activity and software control. Computers that can turn themselves off when you tell them to shut down use ATX power supplies. Full size ATX boards are 305mm by 244mm. Mini-ATX boards are 284mm by 208mm. Both should fit in any ATX case.

BIOS: The BIOS (Basic Input-Output System) is the code a PC runs when it's booted to build enough of a brain to start booting its operating system. Flash-upgradable BIOS chips are the current standard - with a special utility, they can be upgraded to newer versions without any chip swapping.

BX chipset: Intel's 440BX motherboard chipset is the current de facto standard for Slot 1 motherboards. It replaced the earlier 440LX, which only supported 66MHz Front Side Bus speed.

DIMM: Dual Inline Memory Module, the current standard package for RAM. Superseded the earlier Single Inline Memory Modules used on Pentium and older motherboards.

EIDE: Enhanced Integrated Drive Electronics is the modern version of the original IDE. EIDE drives are often referred to as "IDE" but they're much better than the original standard. Both IDE and EIDE have the hard disk controller built onto the drive. If the drive is set to "slave" mode it must be connected to another drive set to "master", whose controller controls both devices. Current PCs have two IDE channels, so in conjunction with the master-slave system a total of four IDE devices can be connected.

Front Side Bus: Processor speed is a product of two numbers, the bus speed (also called Front Side Bus, or FSB), and the multiplier.

The FSB speed is the speed at which the processor talks to the rest of the computer, and is by default 66MHz for almost all processors up to 333MHz, and 100MHz for 350MHz and faster processors. Many motherboards support other FSB speeds - 75, 83, 112 and 133MHz, for example - but non-standard FSB speeds usually entail non-standard PCI bus speeds, since the PCI bus speed is set as a fraction of the FSB speed and is only likely to be the correct 33MHz when you're using an "official" FSB speed. Old motherboards set PCI speed as half of FSB, which makes FSB speeds above 75MHz very tricky. Clock your PCI devices too fast and they may work. Or they may not.

The multiplier is the ratio between the processor's speed of operation and the FSB speed. A 66MHz FSB and a 4.5X multiplier gives you a 300MHz processor. So does a 100MHz FSB and a 3X multiplier, but the faster FSB in the second case will make the computer perform (very slightly) better.

IrDA: The Infrared Data Association came up with the standard wireless infrared data transmission protocol, which give roughly parallel port speeds between devices so equipped - provided they're close to each other, and there's nothing between their IrDA ports. IrDA is used in many ultraportable computers.

ISA: The ancient Industry Standard Architecture (ISA) was introduced with the IBM PC/XT and survives in Plug And Play-enhanced form in modern PCs.

PCI: Peripheral Component Interconnect, the PC expansion card standard that supplanted ISA for higher performance devices. PCI is a cross-platform standard, used by IBM compatible, Macintosh and other computers. A card compliant with the PCI 2.0 standard can, theoretically, operate in any PCI-equipped computer, although the essential driver software may not be available for all platforms.

Ultra DMA/33: The current standard for low cost hard drives, Ultra DMA is the protocol used by Ultra ATA drives to transfer a theoretical maximum of 33.3 megabytes of data per second. This peak speed ca only be approached when data is being delivered by the hard drive's on-board cache memory, though; actual drive performance is considerably lower.

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