PC 99 is a hardware and software specification for various types of PCs: Consumer PCs, Office PCs, and Entertainment PCs, including mobile PCs. Windows CE portables are not covered.
Certified PC 99 compliance gets you a nice "Designed for Microsoft Windows" logo on your box.
Software plays a large part in achieving PC 99 compliance. Having a driver for both Windows 98 and Windows 2000 is a requirement for all PC types. If a driver is bundled with a PC when it is sold, it must pass the PC 99 compliance tests.
The PC 99 specification says that a driver must not use INI files, just the registry. INF style installation must be used, if possible. Drivers must be installed in the correct directories. A driver must not use the same filename as a system driver. A driver must be installable without user input. If a driver has any special parameters, a help file for these must be provided.
WDM drivers must fit in with all the bus specifications and device class driver specs.
The PC 99 specification is in the MSDN Library CD Books section. It has many useful appendices and checklists. There are required, recommended, and optional features.
The specification is also available in book form. The PC 99 System Design Guide, version 1.0 is available from Microsoft Press (ISBN 0-7356-0518-1).
The general drift of the specification is to move PCs away from the traditional IBM-compatible PC to one dominated by PCI, SCSI, USB, and IEEE 1394 devices. No ISA slots are now allowed!
For each PC type, it defines what standard devices must be available and what are the possible options. For example, a basic PC (a 300Mhz Pentium with MMX with 32Mb memory) must have hard disk, keyboard, mouse, serial, and parallel ports, V.90 modem, a graphics adapter, and two USB ports. If possible, most external devices should use the USB bus.
Standard PC options include wireless operation, DVD drive, network card, floppy disk, audio, MPEG-2, video input and capture, and a TV tuner.
A PC should attempt to reduce the Total Cost of Ownership (TCO) by supporting Plug and Play and OnNow Power Management.
Plug and Play uses the ACPI specification to ease the management of resources as devices are added or removed from the system. Insertions or removals while the power is on (hot-swapping) is supported on appropriate buses.
The OnNow initiative aims to make PCs start up quicker. The PC can be put to sleep, in effect, rather than turned off completely.
It is recommended that the physical design and software support the accessibility initiatives.
The core hardware specification for PCs has hardly changed in years (i.e., it should be hardware compatible with the IBM AT specification).
This original specification defines standard hardware peripherals, either on the system motherboard or on plug-in cards. A PC needed a timer, keyboard controller, interrupt controller, real-time clock, two DMA controllers and page registers, serial ports and parallel ports.
Other peripherals soon became standard (e.g., IDE disk drives, CD-ROM drives, sound cards, and network cards).
These original devices had standard places where they had to live (e.g., they had set I/O port addresses, IRQ levels, and DMA lines). These are listed in Tables B.1, B.2, and B.3.
These devices were originally implemented by a host of different chips on the motherboard. Soon, chipsets appeared that combined all these devices.
Table B.1 Legacy ISA hardware system I/O (PC 99)
| I/O Address | Default system function |
|---|---|
0000-000F | Slave DMA |
0010-0018 | System |
0001F | System |
0020-0021 | Master 8259 |
0040-0043 0048-004B | Programmable interrupt timer (PIT) #1, PIT #2 |
0050-0052 | System |
0060 | Keyboard/mouse controller |
0061 | System control port B |
0064 | Keyboard/mouse status |
0070-0071 | Nonmaskable Interrupt (NMI) enable/real-time clock |
0081-008B | DMA page registers |
0090-0091 | System |
0092 | System control port A |
0093-009F | System |
00A0-00A1 | Slave interrupt controller |
00C0-00DE | Master DMA controller |
00F0-00F1 | Coprocessor busy clear/reset |
0170-0177 | Secondary IDE controller |
01F0-01F7 | Primary IDE controller |
0201 | Joystick interface |
0220-022F | Sound Blaster |
0278-027A | LPT 2 (XT parallel port 3) |
02E8-02EF | Alternate COM (4) |
02F8-02FF | COM2 |
0330-0331 | MPU-401 |
0376 | IDE Controller |
0378-037A | LPT1 (XT parallel port 2) |
0388-038B | Frequency modulation (FM) synthesis |
03B0-03BB | MDA, EGA/video graphics array (VGA) |
03BC-03BE | LPT 3 (XT parallel port 1) |
03C0-03DF | EGA/VGA |
03E0-03E7 | PCIC PCMCIA controllers |
03E8-03EF | Alternate COM (3) |
03F0-03F7 | FDC |
03F8-03FF | COM1 |
0534-0537 | Windows Sound System-compatible |
0CF8-0CFB | Peripheral Component Interconnect (PCI) ports |
Table B.2 Legacy hardware IRQ assignment (PC 99)
| Hardware IRQ | Default assignment |
|---|---|
| IRQ 0 | System timer |
| IRQ 1 | Keyboard |
| IRQ 2 | Second programmable interrupt controller (PIC) cascade |
| IRQ 3 | COM2 |
| IRQ 4 | COM1 |
| IRQ 5 | Sometimes LPT 2 — not considered fixed |
| IRQ 6 | Standard floppy disk controller (FDC) |
| IRQ 7 | LPT1 |
| IRQ 8 | Real-time clock/CMOS |
| IRQ 9 | — |
| IRQ 10 | Sometimes COM 4 — not considered fixed |
| IRQ 11 | Sometimes COM 3 — not considered fixed |
| IRQ 12 | PC/2-style mouse |
| IRQ 13 | Coprocessor |
| IRQ 14 | Primary Integrated Device Electronics (IDE) controller |
| IRQ 15 | Secondary IDE controller |
Table B.3 Legacy ISA hardware DMA considered fixed (PC 99)
| Hardware DMA | System function (default) |
|---|---|
| DMA 0 | ISA expansion |
| DMA 1 | |
| DMA 2 | FDC |
| DMA 3 | extended capabilities port (ECP) parallel port on LPT 1 |
| DMA 4 | DMA controller cascading |
| DMA 5 | |
| DMA 6 | |
| DMA 7 |
Over the years, various hardware developments have seen the light of day, such as MCA, EISA, PCI, and SCSI buses, with Plug and Play capability. Not all these developments have won market support.
PC 99 still supports all these "legacy" peripherals, if they are present in the system.
PCs have a Basic I/O System (BIOS) in ROM that runs when the computer is first switched on. This ROM finds the relevant operating system and runs its boot loader to start DOS, Windows 98, Windows 2000, or whatever.
Most programs that are used nowadays run using Win32 (or at least Win16) functions. These routines do not allow direct access to I/O ports, etc. For example, when keyboard input is required, W98 or W2000 carries out the necessary operation. In the IBM-compatible environment, it interacts with the keyboard controller using techniques dating from time immemorial.
Less DOS applications are being run. In W98, NT, and W2000, these do not get direct access to the hardware. Instead, a Virtual Device Driver arbitrates access to these peripherals, allowing multiple DOS and Windows applications to run at the same time.
These two developments allow the Windows operating systems to move away from the original IBM-compatible specification. As long as the right keystroke messages get through to user programs, it does not matter where in hardware they come from. For old DOS programs that do try to access the actual hardware, virtual device drivers on faster new machines can emulate the required functionality.
The new wisdom is that the USB and IEEE 1394 (originally called FireWire) devices represent an easier way for users to connect assorted peripherals to the system, including standard system components such as a keyboard and a mouse. The idea is that any devices can be plugged in easily (even when the computer is on) and — within limits — daisy chained together. USB and IEEE 1394 devices cope with being plugged in anywhere. The Windows Plug and Play system sorts out any resource allocations on the fly.
Whether users will take to the new doctrine remains to be seen. Plugging a new USB device in will certainly be easier than dismantling a case, fiddling with jumpers, and inserting a card. The new Device Bay specification will allow easy insertion of cards within the chassis of the PC.
USB's 12Mbs is designed for slower-speed devices, such as keyboards, mice, joysticks, printers, modems, telephones, and monitors. IEEE 1394 runs faster, at 100 Mbs or more, and is more useful for devices such as scanners, storage units, and audio/visual kit, such as digital cameras.
New PCs aim to use less power and switch on more quickly, as well as supporting Plug and Play. Windows and new BIOS chips use the Advanced Configuration and Power Interface (ACPI) specification to help with these tasks.
ACPI-based hardware knows how to turn off or reduce power to some devices. Windows drivers can now help in this process by using the Power Management IRPs and routines, and the power management routines that are relevant for its device class. The aim of the OnNow initiative is that a PC may appear to be off, when in fact it is just "sleeping", waiting for a soft power on button to be pressed. As the operating system and drivers are already loaded into memory, it takes less time to start up the system. Devices simply need to be powered up for the user to get started. A remote control handset or incoming modem call may similarly be used to wake the system up.
Both Windows 98 and Windows 2000 can now take full use of the Plug and Play hardware facilities to allow easy device insertion and removal. Again, drivers need to help in this process, allocating and releasing resources only as instructed by the Plug and Play Manager.
PC 99 specifies that ACPI, OnNow, and Plug and Play must be supported.:
Microsoft can certify your hardware and software as PC 99 compatible. To do this, contact their Windows Hardware Quality Labs at http://www.microsoft.com/hwtest/ or e-mail to whqlinfo@microsoft.com. When your driver passes these tests, Microsoft gives you a digital signature catalog file that you should include in your driver's INF file.
The Windows DDK includes a simplified version of Microsoft's own tests on their Hardware Compatibility Tests (HCT) CDs. Check out your driver with these tests before submitting your driver for full testing.