gms@psuvm.bitnet.UUCP (02/05/87)
I received the following information from Skip Grandy at the University of Pittsburgh Computer Center. His phone number is (412) 624-6355. His full address is at the end of this posting. ------ Connecting a Xerox 8700 / 9700 Online to a VAX / VMS Computer Using DDCMP Protocol On October 20, 1986 the University of Pittsburgh became operational with an online DDCMP connection between a VAX 8600 computer running the VMS operating system (4.3) and a Xerox 8700 printing system using DEC DMR11 interfaces. A DMR11 installed in the PDP11 control computer in the Xerox 8700 on campus communicates directly with another DMR11 installed in a DEC VAX 8600 at the central computer center located approximately six miles away. This accomplishment was the result of a research and development effort between Computing and Information Systems of the University of Pittsburgh and Xerox Corporation. Xerox is now considering offering this as a product. Please read about the following features and show your interest by sending a letter with comments and/or advising your Xerox representatives so that it can be factored into the decision by Xerox. If there is insufficient interest expressed in this approach, Xerox will not bother to market it as a product. Design features of this work include: A) Bidirectional path instead of the unidirectional approach of 3211 printer emulation using the bus and tag interface to the Xerox 8700. This permits files modified on the Xerox 8700 to be uploaded to the host VAX computer for backup. The only exception to this is proprietary font files. Such font files may only be downloaded from the VAX. Our Xerox 8700's do not have the tape drive options installed on them with a resulting savings in cost. Our need for tape drive service for Xerox software distribution is handled by the tape drives attached to the VAX computer. B) Wide range of bandwidth for remote or local operation. The DMR11 interface can operate from 2400 bits per second to 1 million bps. We have routinely debugged this project using Racal-Vadic model 2400PA modems operating synchronously to connect a Xerox 8700 in El Segundo to the VAX:8600 in Pittsburgh. We have now upgraded the bandwidth for our production unit on campus from 56 Kbps to to 288:Kbps. This was conveniently available on our General DataComm Megamux channel bank and more than sufficient to keep bandwidth from being a bottleneck to full printer speed. C) Realtime online feedback of accounting data for each job. Accounting information is fed back over the bidirectional interface path as each job is completed. This is in comparison to the other Xerox 8700 options of paper, magnetic tape or the 850 communications link. This feature has a problem currently as we find it necessary to concatenate jobs on the VAX in order to avoid the time involved in cycling the Xerox 8700 print engine between an operational and idle state for each of the small jobs sent. If we did not combine them into bigger jobs, we would have an unacceptable throughput rate due to the large number of small jobs which we process. We expect to complete testing software by March 1987 which will achieve this goal of accounting data feedback on a job basis without slowing down the printer. The Xerox 8700 software will be concatenating the jobs from the VAX as reports of a larger job within the Xerox 8700. It will then feed back the accounting data it receives for each report to the VAX as an individual job accounting item. We will then have accurate data for jobs which may have been aborted or changed for some reason by the Xerox 8700 operator instead of the current situation of processing the print data on the host and estimating how many pages and images were created. D) Approach with DMR11 is applicable to all DEC VAX computers. Even the newest members of the VAX line with VAXBI interfaces offer a Unibus option to which the DMR11 connects. E) Not dependent on the DMR11 interface. The key to this implementation is the DDCMP protocol. For example, while it has not been tested, we believe that the only one change is necessary to enable the VAX code to run under MicroVMS on a MicroVAX. This would be to change the pointer to the device driver which has the DDCMP support on the MicroVAX. The most likely device for a MicroVAX is the DMV11 interface. Likewise on the mainframe VAX computers, if a more desirable DDCMP product became available, only changing the pointer to the new driver routines would be required to implement it. To support a device other than the DMR11 on the Xerox 8700/9700, only a new software device driver would have to be implemented. F) Automatic setup for all types of output. The Xerox 8700 operator does not have to use the console to change setups for the different types of output. This is all handled automatically with the insertion of DJDEs by the VAX print symbiont for the different job characteristics. This avoids manual intervention and thus improves throughput. G) Reasonable hardware costs. While the current list price for a DMR11-M board set is $ 4,975 and $ 290 for any model of the cabinet connector kit from DEC, they are currently available from third parties for less than half of this. The DMR11 supports five methods for communications: RS232, RS422, RS423, V.35, and an Integral Modem. Installation of a particular cabinet kit determines which method is to be used. From DEC, a MicroVAX DMV11-M (RS232/422/423) is $ 2,125 and DMV11-N (V.35/Integral Modem) is $ 1,800. The DMV11 cabinet kits are $ 270 (RS232/422/423), $ 740 (V.35) and $ 440 (Integral Modem). H) Security from users submitting their own DJDE entries. The VAX print symbiont does not permit unauthorized use of DJDEs from users. This is accomplished by the VAX print symbiont processing the user data and preventing it from being in the form which the Xerox 8700 is recognizing as a DJDE record. The Scribe output which needs to pass DJDEs is identified and reformatted to permit it to do its page layout. I) Simultaneous connection to both a VAX and IBM mainframe. The DMR11 installation in a Xerox 8700 was put in available Unibus slots of the PDP11 control computer and did not displace any other interface. It is possible to have the Xerox printer connected to both a DEC VAX computer and an IBM mainframe in either a local or remote type of configuration. The software in the Xerox 8700 does not permit it to be active with both interfaces simultaneously but by simply using the Xerox 8700 console, one interface may be shut down and the other interface activated. This would occur with no changing of cables. One use of this would be to permit two Xerox printers to be crossconnected between a VAX and IBM mainframe to permit load sharing and a backup capability to exist for an out of service printer. Likewise 850/860 CWP equipment may also be cabled in at the same time but may not receive data at the same time as the HIP or Bus & Tag interface. J) Remote printers can backup each other. Some businesses have multiple Xerox 8700/9700's in different locations, even including different cities. By obtaining a leased or dialup service at 56 Kbps, it becomes easy to configure a situation which would permit such machines to serve as backups for each other. The data rate of 56 Kbps should be quite sufficient to drive a Xerox 8700 at full speed with text data. While 56Kbps would not be sufficient to operate a Xerox 9700 at full speed, it may well be adequate for a backup mode. K) Able to print any size output. Like the line printer (3211) interfaces, any length output may be printed using this DDCMP software. This is not a feature of the Interpress/Ethernet/CWP interface. The software handling Interpress cannot begin the printing process until the job has been completely received onto the Xerox spooling disk. The DDCMP approach passes data for printing a job while it is also receiving additional data for the same job and therefore does not restrict the length of any output file. L) Support for many types of output. Support in this VAX print symbiont exists for: Computer output with forms overlay Standard Scribe output Scribe output with merged graphics * Plot output from DISSPLA/TEL-A-GRAF * * This feature requires another University of Pittsburgh proprietary VAX program which rasterizes Zeta GML plotter code. M) Software consumes small amount of resources. The VAX print symbiont code requires fifty six blocks (512 bytes per block) of disk space. CPU resource requirements are kept small by using the DMR11 which is a DMA device. The CPU utilization of the print symbiont on a DEC VAX 8600 is .001 CPU seconds per 512 byte sector of output. N) Limit of 128 possible characteristics. In the Environmental Characteristics section of the reference manual it notes that there is a limit of 128 possible characteristics for the print jobs. This is a DEC VAX/VMS limit which is noted in the DEC DCL manual under DEFINE/CHARACTERISTIC. We did not implement forms control with the FORM option of VMS because to use it would require manual intervention. An operator would be required to control the print queue in order to switch from one form type to another. Instead, this implementation permits different forms types on the Xerox 8700 to be automatically selected by DJDEs issued by the print symbiont. O) Future possibilities. We are looking at TEX and XICS as other possible formats which can be handled by the print symbiont. This would permit them to pass their DJDEs to the 8700/9700. It would also be possible to have a generic format designed which would permit any user to send their own DJDEs. The University of Pittsburgh has two Xerox 8700 printing systems. The Administrative Xerox 8700 is currently connected directly to the NAS 8053 via a bus and tag channel extender. We are currently looking at products which will provide a high bandwidth communication path between our NAS 8053 IBM compatible mainframe and our now upgraded VAX 8650 VMS 4.5 mainframes. This will then permit us to direct connect our Administrative Xerox 8700 as well as the Academic Xerox 8700 to our VAX computers. Output for Administrative and Academic users may then be routed to the printer most appropriate to speed delivery to the user. For further information contact: Allen Grandey University of Pittsburgh Computing and Information Systems 600 Epsilon Drive Pittsburgh, Pa. 15238-2887 (412) 624-6355 ASG 1-7-87 Bitnet ASG@PITTVMS