GB2152787A - Multiprocessor system - Google Patents

Abstract

In order to render a microprocessor and its peripherals available to a number of user stations, the microprocessor is located at a central station, and is accessible to the user stations via digital links. The connections needed to provide access from a user station to the central station, or vice versa, are set up in normal "digital exchange manner" via the telecommunication system, which is usually a digital PABX. The information to be sent for the computing purposes is sent using one of the industry-standard data transmission speeds. With several microprocessors at the central station access is via a hunting group number, or one of two or more such numbers for different computing applications.

Description

SPECIFICATION Multiprocessor system The present invention relates to digital computing systems.

Afeature of modern offices is the number of free-standing microcomputers, often linked by local area networks. This trend is allied to the trend towards decentralisation of data processing, which may involve the use of a free-standing microcomputer serving, e.g. an individual ora small group of engineers orfinancial planners, with perhaps some communication capabilityforthetransferoffiles between microcomputers and to access a database, to which it may have read-only access. The user department in such a case runs its own applications and maintains its own files.

A microcomputer is relatively expensive and not readily portable, so in a typical office a large investment is needed to provide a microcomputer per person needing access to one, and in practice the microcomputers are provided to a large extent on a pooled basis, requiring waiting for access and moving of stafffrom their normal workstation in many cases.

According to the present invention there is provided a digital processing system, which includes user stations each having one or more peripherals including digit sending and receiving means, and a central station which includes at least one microprocessor and associated peripherals, wherein the conveyance of digital information between a user station and the central station, or between the central station and any one ofthe user stations ofthe system is effected digitally,wherein the information sent from the user station to the central station when the user initiates a connection includes information identifying the apparatus at the central station to which access is desired, wherein the information sentfrom the central station to a user station includes information identifying the userstation forwhich that information is destined, and wherein the information transfer between the user stations and the central station in both directions takes place over communications paths set up via a digital telecommunication system such as PABX.

In known systems the microcomputer is based on a microprocessor connected by a bus to varioustypes of memory and mass storage devices, and in many cases a local network interface. To this bus are also attached viainput'outputportsthe peripherals,such asthe keyboard, display screen, etc.

Thus the invention describes a method of removing some parts of a microcomputer installation from the user location to a remote central site, and providing each userwith a basicsetofperipheralswhich he can connectto the aforesaid removed parts of the microcomputer by digital switching andtransmission means An embodimentofthe invention will now be described with reference to the accompanying drawings, in which Fig. lisa schematic diagram of a data terminal with character display, as used in a system embodying the invention, and Fig. 2 is a schematic diagram of a remote microprocessor in a system embodying the invention, and Fig. 3 is a schematic diagram of a data terminal usable in a system embodying the invention, but simpler than the termin al of Fig. 1.

A system embodying the invention uses known techniques of digital transmission and switching, as applied in digital PABX's and transmission channels, to enable some or all of the peripherals of the microcomputerto be located at a user station remote from the microcomputer, memory, mass storage and other microcomputer components. The components at the central station arethose which do not need to be co-located with the user, who has a basic set of peripherals according to his needs. These peripherals are attached to a digital PABX circuit.

From hissetof peripheralsthe usercan setup a call to a remote microcomputer and use the facilities of the microcomputer as if his peripherals were directly attached to it. The available microcomputers if more than one may be arranged on a hunting group number, as in known PABX's, so that the user's needs may be met by connection to any microcomputer in a group supporting a given application or set of applications. Different hunting group numbers may be used to access other groups of microcomputers supporting other applications.

The switching and transmission means used may be either analogue or digital, according to the known art, butthetransmission means must be fast enough to provide the necessary speed of response as seen at the user station. The use of digital switching and transmission means, such as provided buy a digital PABX with digital transmission ports, or by a local packet network, as known in the art, is preferred to provide the necessarytransmission speed to support commonly-used peripherals such as keyboards, characted and graphic screens, printers and direct input devices such as rolling balls or 'mice', at an acceptable cost.

Ifthere are more than one input peripheral atthe user station, the input side of the circuittermination at the user station incorporates a concentrator circuit. A similar arrangement is used on the output side if there is morethan one output peripheral. The input concentrator circuit ensures that data or character sequences sent to the microcomputer via the transmission means are associated with an indication of the input peripheral from which they originated. The output concentrator circuit ensures that data or character sequences sent from the microcomputer via the transmission means, and associated with an indication ofthe output peripheral to which they should be sent (the data or character sequence and associated indication having been sent by the circuit termination atthe microcomputer) are sent to that output peripheral.The method of sending such an indication in either the input orthe output case vary in different implementations ofthis invention, and are related to the method of transmission used with packettransmission,the indication can be in the packet format. If un packetised transmission is used, and an out-band signalling path is available, the indication can be sent by end-to-end signalling (prior to the sending of the characters), between the user station and the microcomputer, using forexamplethe signalling path associated with a digital transmission means. Alternatively, a sub-multiplex ofthe channel can be used for each peripheral.End-to-end signalling can also be used if necessaryto enable the circuit terminations at the user station and at the PABX to adjustthetransmission speed ofthecircuitto match that of the peripheral. The aforementioned techniques are well known.

We now referto Figures 1 to 3, which showthe invention implemented with the use of digital transmission circuits and a digital PABXto support two different user station configurations. We considerfirst the case of a user station with four peripherals, see Fig.

1. At the start ofthe session, the user establishes a connection with the computerfacilityfrom the keyboard 1 using a call set-up procedure. This is initiated by depression of the Call button, which causes the digital circuittermination 2to place the connections between itself and the keyboard and display peripherals 3 and 4 into signalling mode.

Peripheral 3 is a printer, and peripheral 4 is a video screen and buffers, etc.

The keyboard 1 is then used to input selection information. Call set-up is by the digital switch (not shown), which communicates with the userstation and the microcomputer on the signalling paths shown in Figs. 1 and 2. Success (orfailure) ofthe call set-up attempt is indicated by the display of an appropriate message on the display 4. The use of a keyboard and displayto set up a data call is well known; the novelty ofthe present system lies in the subsequent use of the keyboard and display as if they were peripherals directly attached to the microcomputer.

The call having been set up, the digital circuit termination 2 places the connections between itself and the keyboard and display peripherals into data transfer mode for the duration ofthe call. Each subsequent operation ofthe keyboard causes a corresponding character sequence to be sent via the data path within the digital transmission and switching means to the remote microcomputer. Each character sequence thus transmitted in in this case encoded in a packet format, the address of the packet indicating the peripheral from which it originated; in this case the keyboard. Thus in this example packetisation is the technique used to effectthe concentration function. In like manner, each operation of the "mouse" 5 causes an encoded packet of data to be sent via the data path within the digital transmission and switching means to the remote microcomputer.

When received bythe remote microcomputer 10, Fig. 2, each encoded packet is decoded by the Digital Circuit Termination component 11 associated with the remote microcomputer 10, Fig. 2, and translated into a corresponding message for transmission on the microcomput6r bus. This message "informs" the microcomputer of the event which has taken place at the peripheral, eitherthe keyboard orthe mouse, and the microcomputerapplication software responds to this as itwould have responded to the same event taking place at a local keyboard or mouse attached to it in the usual manner.Similarly, when the microcomputer software is readyto initiate an event at an output peripheral, such as the display of a line on the screen, this is done by generating a message on the microcomputer bus to the digital circuit termination 11, which is encoded into a packet. This packet is sent to the userstation via the switching andtransmission means, and is decoded by the digital circuittermination. The data or character sequence contained in the packet is sent to the peripheral indicated by the packet address, in this case eitherthe display ofthe printer. At the end of the session, the clear button is operated to clearthe PABX call.The user station peripherals are now disassociated from the remote microcomputer, and signalling between the user station and the PABX and between the PABX and the remote microcomputer results in the PABX clearing the switched circuit connections, and the remote microcomputer becoming free to accept calls from other user stations.

The other elements of the microcomputer facility are its memory 12, its fixed disc control unit 13, and a network interface 14, which gives access to mass storage, other microcomputer main frames, etc.

A simpler user station configuration is shown in Fig.

3. Here there is only one input peripheral,the keyboard 20 and one output peripheral,the display 21.

In this case therefore, there is no need to use packetisation, submultiplexing or additional signalling to indicate the association between a data or charactersequence and its associated peripheral, which simplifies the digital circuit termination circuits at the user station and atthe remote microcomputer.

In otherrespectsthisexampleisthesameasthat illustrated in Fig. 1 and described above.

A great deal of software development effort goes into the development of operating systems and application packages, and there are established microcomputer operating systems such as CPtM and Unix, which are well known and many software packages are based on CP/M or Unix. It is straightforward for anyone skilled in the artto instal such systems and packages on the microcomputer systems described herein.

The advantages of the present system are: a) The availability of a pool of microcomputer systems on a PABXhunting groupnumberincreases utilisation. Asmaller number of microcomputer systems is needed to serve a given number of users.

b) The microcomputer system user has the increased security offiling, archiving, etc. undertaken as part ofthe microcomputer system pool facility. The user is also freed from the need to provide protected storage spaceforfloppy discs, and periodicfile regeneration.

c) When the ISDN (Integrated Systems Digital Network) reaches domestic users, the ever-increasing numbers of office staffworking from home will be able to access the microcomputer system pool on the same basis as staff at the office.

d) Many forms of mixed working are possible, e.g.

most microcomputer system users increasingly tend to use packages ratherthan develop their own programmes. Hence it is possible notto provide developmenttools on the microcomputer systems, butto use a locally-attached microcomputer system during programme development.

e) The keyboard/screen "cluster" is available for switched connection to existing time-sharing services, via the PSTN (Public Switched Telephone Network) or ISDN. Asuitable gateway unit (protocol converter) attached to the PABX is needed.

f) The individual remote microcomputer user istoa large extent "future-proofed" by the use of this terminal.The remote microcomputer(s) can have greater processing power and storage access capabilits than is possible for all but a few dedicated microcomputer users. As the remote user's processing and storage requirements increase, they remain, initially at least, within the application base's capability, which can itself be expanded by adding further microcomputer ports, mass storage and other peripheral devices on a local network basis, according to the growth oftheorganisation'soverall requirements. At a later stage it is possible to provide an enhanced terminal, e.g. with colourgraphicfacilities, to coincide with the enhancement ofthe application base to supportsuch a terminal with appropriate application software. This is a cheaper growth path than the equivalent replacement of a dedicated microcomputer would be.

Claims (8)

1. Adigital processing system, which includes user stations each having one or more peripherals including digit sending and receiving means, and a central station which includes at least one microp rocessor and associated peripherals, wherein the conveyance of digital information between a user station and the central station, or between the central station and any one ofthe user stations of the system is effected digitally, wherein the information sent from the user station to the central station when the user initiates a connection includes information identifying the apparatus at the central station to which access is desired, wherein the information sent from the central station to a user station includes information identify ingthe userstation forwhich that information is destined, and wherein the information transfer between the user stations and the central station in both directionstakes place over communications paths set up via a digital telecommunication system such as PABX.

2. Asystem as claimed in claim 1, wherein the central station includes two or more microprocessors availableforuseforthesame computing applications, and wherein the information sentfrom a userstation which identifies the central station causes hunting overthe said microprocessors in search of one which is free for use.

3. Asystem as claimed in claim 2, wherein there aretwo ormoregroups of microprocessors, each such group being available for use for different computing applications, and wherein the central station has two or more call numbers, one per microprocessor group with each such call number causing said hunting over the microprocessor of only one of said groups.

4. A system as claimed in claim 1,2 or 3, and wherein the apparatus at a user station includes, in addition to the digit sending and receiving apparatus, one or more other devices for supplying input information to and/or receiving information from a microprocessor.

5. A system as claimed in claim 4, and wherein each peripheral art a said user station is connected to a digital circuittermination which in turn gives access to a connection to the digital telecommunication system.

6. A system as claimed in claim 5, and wherein the digital circuittermination incorporates a concentrator circuitto enable more than one peripheral to be attached to a single circuit, and wherein signalling means ensures that the digital circuit terminations at the user station and at the microcomputer address the intended peripheral and apply the appropriate rate adaption to the transmitted character sequences, if necessary.

7. Adigital processing system, substantially as described with reference to the accompanying drawings.

New claims or amendments to claims filed on 1 2th April, 1984.

Neworamendedclaims:-Claim 8.

8. A digital processing system, which includes user stations, each having a plurality of peripherals including digit sending and receiving means, and a central station including at least one microprocessor and associated peripherals including memory means, wherein the conveyance of digital information between a user station and the central station or between the central station and any one of the user stations of the system is effected digitally, wherein the information sent from a said user station to the central station when the user initiates a connection includes information identifying the user station and information identifying the apparatus (microprocessor and one or more peripherals) at the central station to which access is desired, wherein information sent from the central station to a said user station includes information identifying the user station for which that information is destined, wherein when two or more connections are in progress between respective ones ofthe users and the central station the conveyance of information occurs in a time interleaved manner as seen by the central station, and wherein the information transfer between the user stations and the central stations in each of the said directions takes place over communications paths set up via a digital telecommunication system such as a PABX, each said peripheral at a said user station being connected to a digital circuit termination which in turn gives access to a connection to the digital telecommunication system.