My ideal PC has no motherboard. Instead it contains space for two backplanes, each of which occupies roughly half the available 'motherboard space'. Each new marque of backplane accommodates one particular type of system bus (eg ISA, PCI, PCIX) and the minimal functionality required to support it. Thus the PC can support 2 system bus types concurrently. One bus (eg an ISA bus) is sufficient for the PC to function fully. A second, more advanced system bus (eg PCI) is installed when it comes into general use. The newer type of system bus is installed in the other half of the available standard motherboard space.
During the time of transition between two system bus technologies, option cards are made to interface with both. Eventually, the older system bus is phased out and replaced with an even more advanced bus type. This allows system bus technology to leap-frog seamlessly without forcing the obsolescence of perfectly good option cards. Each developmental leap in bus technology thus has to be designated as an upper or lower bus type so that option card edge connectors can be made to mate with the appropriate bus type.
My ideal PC bus has two priorities of power rail. One is for powering things when the PC is switched on and running. The other is an essential power rail for keeping alive circuitry which must remain in a standby mode ready to wake up the PC whenever a relevant external event occurs. In some cases, this standby power is supplied by a serial bus power wire from the external equipment that needs to wake up the PC.
The CPU card accommodates my ideal PC's Northbridge chip and everything to the 'north' - namely the CPU, the main memory and the CPU's external cache memory if relevant.
This card has extra space to the right to allow large components to stand off the card - eg CPU cooling sink and memory modules.
My ideal PC contains a Java 'Real Machine' co-processor card. The co-processor is a hardware chip that runs Java Byte Code directly as its native instruction set. Dream on, Rob!
This special CPU has its own dedicated on-card memory. Naturally, this memory is part of the my ideal PC's main CPU address space. However, it is also the 'sandbox area' outside which the Java Real Machine, and the Java Byte Code it is running, cannot stray. My ideal PC is thus protected directly by hardware against any rogue Java applets that may be downloaded from the Internet from time to time.
The Java 'Real Machine' co-processor card also accommodates the core Java classes (eg: java.lang.*) in ROM, and the other generic Java classes (which are likely to change from one version of Java to the next) in Flash ROM.
Also on the Java 'Real Machine' co-processor card is a Java Just-in-Time compiler. This allows me to run bits of Java source code like we used to run ROM BASIC source code on the original IBM PC. This is ideal for prototyping bits of program - especially when developing scientific and engineering applications. It is also useful for gluing together applications with fragments of Java instead of having to remember the syntax of goodness knows how many Operating System scripts.
My ideal PC can thus run Java programs fast and securely without placing any load on the PC's main resources.
Video technology seems to me to be changing ever more rapidly.
The latest idea seems to be to have a separate AGP bus for video adapters. Video does demand far more band width than anything else in the PC. Having a dedicated video channel direct to the CPU does therefore make sense. It can also claim precedent from that ultimate of computing devices - the human brain, which has what could be regarded as a dedicated video sub-system. Notwithstanding, in order to maintain consistency and upgrade flexibility, my ideal PC has its video adapter on the system bus.
My ideal video adapter has on-card upgradeable processing for decompressing compressed image file formats, and video file and stream formats. It also accommodates - within a Flash-ROM - upgradeable functionality for a variety of GUI styles.
My ideal sound card naturally includes a built-in upgradeable MIDI system. It also contains CD and DVD format handlers.
Its most important application for me is as a programmable digital signal processor which can be 'flashed' with downloadable and DIY programs. For me, these would be for handling such things as the AMTOR, PACTOR, G-TOR, PACTOR-2, RTTY, PSK31, HF Packet, MT63, THROB, MFSK16 transmission modes used in amateur radio.
My ideal sound card also has an on-card encoder for converting analogue voice signals from a microphone into a 56 or 64 kbps stream for use by external devices like a digital spread-spectrum transceiver.
Connections between my ideal PC and all its internal and external peripherals are effected using several instances of a standard high speed serial bus. Under current technology the very high data rate required by the screen and perhaps the Future Technology Storage Devices would require an IEEE 1394 bus. For my ideal PC's other peripherals, a Universal Serial Bus should suffice. Hopefully, these two bus standards will be merged later into a single specification with enough flexibility to handle all PC peripherals.
The ports card of my ideal PC provides ports for both current high speed serial bus standards for connecting peripheral devices which are accommodated both inside and outside my ideal PC's 'system unit' chassis.
I like the idea of a Network Interface Card which has several piggy back holders for individual Network Interfaces. This allows my ideal PC to interface to more than one network from a single system bus slot.
Of all the network types, philosophically I prefer Ethernet. Of its variants I prefer the nBase2 coax type. Although more expensive, I think it is more reliable and secure than open twin. Besides, I like its egalitarian regime in which all clients are equal citizens without a king. In other words, it has no hub unit.
The same full size expansion card also contains an IEEE802.11b wireless local area network interface. This may require a separate 2.4 GHz wireless transceiver in an internal peripheral module in one of the '3½ inch drive' bays above the option cards.
My ideal modem card has all its functions clearly visible on the card. It also has a separate audio input to the demodulator and output from the modulator so that it can be used with radio equipment as well as a normal dial-up telephone line.
This is the 'Southbridge' of my ideal PC. It has plug-in piggy back boards or LSI chips for its diverse functions.
Its primary function is to provide universal time for the PC as a whole. It is capable of receiving an external time signal from various sources such as GPS satellites or standard frequency transmissions like MSF and WWV. It automatically corrects its on-card quartz clock module at least once per hour when signals are present. It is able to wake up the PC at pre-set times and supplies the PC's time reference while the PC is running.
Since to acquire GPS time it must have a GPS receiver, this option card also provides accurate location information - ie latitude, longitude and height. This is useful both in the case where the PC is in a mobile installation and in the case where the PC is fixed to provide a differential GPS correction to local mobile units.
My ideal PC's services card also has sockets for piggy-back DIY plug-ins. These I would use to indulge my own interests in devices which use natural sources of time and location information such as rotating neutron radio stars of known location and pulse period.
Other functions on this ideal option card are environmental monitoring, power and backup management, and system temperature regulation.