1. FIELD OF THE INVENTION

The present invention relates to a low-cost extension of a standard DOS-based (i.e., x86) personal computer (PC) running a Windows, Windows NT or Windows 95 operating system to run Unix-based applications concurrently with DOS-based applications, and more particularly to a SPARC/Mbus-based computer designed to be easily interfaced with a standard DOS-based PC by physically inserting the SPARC computer into a full-height standard 5.25 inch disk drive bay of the PC chassis, the PC machine coupled to the SPARC machine through an ethernet connection or a SCSI bus and thus capable of launching SPARC applications to run on the SPARC machine concurrently with PC applications running on the PC machine.

2. ART BACKGROUND

In the past, computing products have been developed to meet different market segments in accordance with the cost/performance point of each segment. Desk-top personal computers have been designed to provide sufficient computing power to run applications normally associated with computing in the home or office, such as wordprocessing, spreadsheets, home finance, video games, etc. Such computers have been primarily designed to run using a DOS-based operating system (e.g. Windows) and the number of commercially available applications programs is countless.

While DOS and the x86 architecture is adequate for running applications such as word processing and spreadsheets, they leave much to be desired with respect to engineering and scientific applications, such as circuit simulation and other math intensive applications requiring numerous floating point calculations, or with server functions. Thus, a whole line of products known as engineering workstations were developed for the desk tops of engineers and scientists, some of these workstations having sufficient computing power to be used as file servers as well. These engineering workstations are typically driven by RISC microprocessors running a Unix-based operating system such as Solaris and running the numerous applications programmed using programming language such as SPARC. These workstations lend themselves well to multiprocessing

architectures, further increasing their computing power. One such workstation is the SPARC Station 20 available from Sun Microsystems, Mountain View California.

With advances in x86 microprocessor and memory architectures and designs, increasing performance has also been achieved at the PC level for a given cost point. Moreover, those using workstations have also found it desirable to have a PC on their desk for those applications more typically handled by PC's. Such users have in the past coupled their engineering workstations to their PC's to initiate and monitor engineering applications operating on their workstations from their PC's while running Windows applications concurrently on their PC's.

Such a coupling of DOS PC and Unix workstation, although highly desirable, is extremely expensive and cost inefficient as there are duplicative resources. Only those who can afford the high cost of an engineering workstations along with the additional expense of the PC can afford this combined computing power. Thus, it would be highly desirable to provide a low-cost solution to the owners or purchasers of desk top PC's which would enable them to enjoy the additional horsepower afforded by a concurrently running Unix-based machine without the need to purchase a full-blown engineering workstation. The added cost of the SPARC -based machine can be minimized by packaging it to fit into a standard 5.25" drive bay (full height) available in most existing PC chassis, and connecting the Unix-based machine to the PC (through both hardware and software) in a manner which permits the Windows operating system of the DOS machine to launch a SPARC application, to monitor the SPARC application and to translate the output generated by the Unix application to a DOS compatible display format. Such a solution has not heretofore been invented. SUMMARY OF THE INVENTION

The present invention is a low-cost extension of a DOS-based personal computer, typically running an operating system such as Windows, Windows NT or Windows 95, to run SPARC-based applications concurrently with DOS-based applications. The DOS PC is a commonly available DOS machine (i.e. x86 based) which has been minimally modified to accept the electrical (but not necessarily the mechanical) interface of a Unix- based (i.e. SPARC Mbus) computer. In the preferred embodiment of the invention, the SPARC computer comprises a SPARC Mbus workstation motherboard which supports one Mbus slot (up to two CPUs) and one Sbus slot. The SPARC-based machine further

comprises up to four 144 bit wide SIMM memory modules, thus supporting up to 256 Mbytes of memory given current memory technology. The Sparc-based machine further comprises an Ethernet connection, a Fast SCSI-2 disk drive and interface, 8-bit audio, keyboard, mouse, floppy disk control and two serial ports. The SPARC machine's operating system is preferably

The SPARC and x86 computers share the PC's power supply, which is somewhat larger than a standard PC power supply to offset the additional power consumption of the SPARC machine (a maximum of 10 Watts at 5 Volts). They also share the Standard PC monitor for display of output. Each machine maintains its own memory and SCSI hard drive. The two computers communicate over an Ethernet connection which is capable of transmitting between one and ten Megabits per second. The two computers can also communicate via a common bus coupled between their respective SCSI bus interfaces.

Additional software is provided so that icons representing the SPARC-based applications can be selected to launch execution of a particular SPARC application. The DOS operating system initiates the SPARC application over the Ethernet connection. Any output which the SPARC machine generates in running the launched application is converted by the DOS (i.e. Windows) operating system for display on the PC's video monitor.

The goal of low cost was partially achieved by designing the SPARC machine to fit into a standard 5.25" slot. This form factor was achieved by confining the SPARC machine motherboard to a size of 196 x 140 mm. Thus, the motherboard, the disk drive, the Mbus card and the Sbus card all fit into a housing which in turn fits the 5.25" slot. The I/O is broken up into two distinct connectors, one for the SCSI interface and the other for the Peripheral I/O (e.g. the Ethernet port, the serial ports, the keyboard, the mouse, audio and the floppy control). The SPARC machine can use its Peripheral I/O port to drive a status monitor and to receive input from a status keypad. The housing is divided into three parts comprising an enclosure base, an enclosure cover and a front bezel. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a high-level block diagram illustrating the electrical interconnections of the present invention.

Figure 2 is a high level illustration of the bus topology of the SPARC machine of the preferred embodiment of the present invention.

Figure 3 is a topological illustration of the motherboard of the preferred embodiment of the present invention.

Figure 4 is an exploded view of the assembly of the SPARC machine of the preferred embodiment.

Figure 5a is a high level representation of the present invention configured to provide a powerful Web Development Tool.

Figure 5b is a high level representation of the present invention configured to be a Web Server.

Figure 5c is a high level representation of the present invention configured to be a Java Development Station.

Figure 5d is a high level representation of the present invention configured as a powerful combination PC and Workstation.

Figure 5e is a high level representation of the present invention configured as a 3-D Design/Rendering Station. DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be discussed in detail with reference to Figures. Figure 1 illustrates a high-level electrical interface between a Standard PC machine (i.e., x86) 22 and a SPARC-based machine 12 as contemplated by a preferred embodiment of the present invention. The Standard PC communicates with the SPARC based machine 12 over Ethernet connection 18. The Standard PC has additional software capable of translating between SPARC and x86 data formats. The Standard PC machine is coupled to a Standard monitor 20, and a standard PC disk drive 24 through a well-known SCSI bus interface. The two machines share the same power supply 10, which has to be able to provide an additional 100 Watts at 5 Volts to power the SPARC-based PC.

The SPARC-based machine 12 also maintains its own memory and hard drive 26, the hard drive 26 also coupled to the SPARC machine via a SCSI interface. The Standard PC and the SPARC machine can also communicate over a common connection 28 between their respective SCSI buses, provided the SCSI interface of at least one of the machines has the ability to translate between SPARC and x86 data formats. The SPARC machine also drives a simple status display and receives input from a simple key pad.

Figure 2 illustrates the bus architecture of the SPARC machine 12. The SPARC machine can have up to two CPUs 50 and 52, coupled through the Mbus 54 to the Error

correcting Memory Controller (EMC) 68, which in turn is coupled to memory located in slots 70. The Mbus 54 also couples CPUs 50,52 to the Sbus 60 through the Mbus-Sbus Interface (MSI) 58. Sbus 60 couples MSI 58 to the Master Controller for I/O (MACIO) 64 and Sbus to Ebus Controller (SETC) 62. SETC 62 couples Sbus 60 to Ebus 63.

MACIO 64 couples the SPARC machine 12 to Ethernet bus 18 and the SCSI bus. SETC couples the SPARC machine 12 to the two serial ports A and B via blocks 72 and 74 respectively, to the Open Boot Prom (OBP) 76, battery backed Ram 78 used for keeping track of time and date, Floppy Drive Controller 80 and Audio interface 82. A more detailed description of the bus protocols and the specifications and functions of the circuit blocks discussed above can be found in the SPARCplug Technical Manual, Version 1.0, May 1996, which is attached hereto as Appendix A and is incorporated herein by this reference.

Figure 3 illustrates a topological footprint of the motherboard 110 of the SPARC machine of the present invention. Those of skill in the art familiar with SPARC workstations such as the SPARCstation 20 available from Sun Microsystems of Mountain View, California will recognize that numerous resources normally available within a full¬ blown Sparc workstation have been cut down or eliminated in order to achieve the compactness required to permit the SPARC machine of the present invention to fit within the 5.25" disk drive bay of the Standard PC 22. For example, there are normally four Sbus slots where there is only one for the SPARC machine 12 of the present invention. There are typically 8 SIMM sockets providing up to 512K of memory as compared to four in the Sparc machine 12. The audio resolution has been trimmed from 16 bits to 8 bits. ASIC chips used for controlling access to the buses etc. have been significantly reduced in size. The I/O of the motherboard was split into two distinct connectors, a high density 50 pin SCSI connector 104 for the SCSI channel and a standard 68 pin SCSI connector 100 for the Peripheral I/O (i.e., ethernet, serial ports, keyboard, mouse, audio and floppy control). Power is coupled to the motherboard via power connector 102. Thus, the motherboard 1 10 for the SPARC machine 12 of the present invention could be maintained at a size of 196mm x 140mm.

Figure 4 is an exploded view of the SPARC Machine 12 of the present invention illustrating its mechanical constituents and their interrelationships. Motherboard 110 is secured to enclosure base 128 as shown. An Sbus card 126 fits in Sbus slot 56 of

motherboard 110, while Mbus card 124 fits into Mbus slot 1 12 of motherboard 1 10. A standard disk drive (not shown) is coupled to the SPARC machine 12 as previously discussed and is also housed within enclosure cover 120. Front bezel 122 completes the enclosure and can frame the status display 14 and keypad 16.

Figures 5a-5e illustrate conceptually various configurations to which such a combination of machines could be put. Those of skill in the art will recognize that there will be many combinations of SPARC and PC applications which could be configured to provide substantial advantages over just a Standard PC. Moreover, the preferred embodiment of the invention as disclosed is intended to be exemplary only and those of skill in the art will recognize that other variations of this invention could be implemented which would fall within the intended scope of the present invention.