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units in separate cabinets the ibm 2870 is the byte multiplexor channel with up to four selector sub channels and the ibm 2860 is up to three selector channels the byte multiplexer channel is able to handle i o to from several devices simultaneously at the device s highest rated speeds hence the name as it multiplexed i o from those devices onto a single data path to main memory devices connected to a byte multiplexer channel are configured to operate in 1 byte 2 byte 4 byte or burst mode the larger blocks of data are used to handle progressively faster devices for example a 2501 card reader operating at 600 cards per minute would be in 1 byte mode while a 1403 n1 printer would be in burst mode also the byte multiplexer channels on larger models have an optional selector subchannel section that would accommodate tape drives the byte multiplexor s channel address was typically 0 and the selector subchannel addresses were from c0 to ff thus tape drives on system 360 were commonly addressed at 0c0 0c7 other common byte multiplexer addresses are 00a 2501 card reader 00c 00d 2540 reader punch 00e 00f 1403 n1 printers 010 013 3211 printers 020 0bf 2701 2703 telecommunications units these addresses are still commonly used in z vm virtual machines system 360 models 40 and 50 have an integrated 1052 7 console that is usually addressed as 01f however this was not connected to the byte multiplexer channel but rather had a direct internal connection to the mainframe the model 30 attached a different model of 1052 through a 1051 control unit the models 60 through 75 also use the 1052 7 cable used as bus or tag cable for ibm system 360 bus and tag terminators selector channels enabled i o to high speed devices these storage devices were attached to a control unit and then to the channel the control unit let clusters of devices be attached to the channels on higher speed models multiple selector channels which could operate simultaneously or in parallel improved overall performance control units are connected to the channels with bus and tag cable pairs the bus cables carried the address and data information and the tag cables identified what data was on the bus the general configuration of a channel is to connect the devices in a chain like this mainframe control unit x control unit y control unit z each control unit is assigned a capture range of addresses that it services for example control unit x might capture addresses 40 4f control unit y c0 df and control unit z 80 9f capture ranges had to be a multiple of 8 16 32 64 or 128 devices and be aligned on appropriate boundaries each control unit in turn has one or more devices attached to it for example you could have control unit y with 6 disks that would be addressed as c0 c5 there are three general types of bus and tag cables produced by ibm the first is the standard gray bus and tag cable followed by the blue bus and tag cable and finally the tan bus and tag cable generally newer cable revisions are capable of higher speeds or longer distances and some peripherals specified minimum cable revisions both upstream and downstream the cable ordering of the control units on the channel is also significant each control unit is strapped as high or low priority when a device selection was sent out on a mainframe s channel the selection was sent from x y z y x if the control unit was high then the selection was checked in the outbound direction if low then the inbound direction thus control unit x was either 1st or 5th y was either 2nd or 4th and z was 3rd in line it is also possible to have multiple channels attached to a control unit from the same or multiple mainframes thus providing a rich high performance multiple access and backup capability typically the total cable length of a channel is limited to 200 feet less being preferred each control unit accounts for about 10 feet of the 200 foot limit block multiplexer channel edit ibm first introduced a new type of i o channel on the model 85 and model 195 the 2880 block multiplexer channel and then made them standard on the system 370 this channel allowed a device to suspend a channel program pending the completion of an i o operation and thus to free the channel for use by another device a block multiplexer channel can support either standard 1 5 mb second connections or with the 2 byte interface feature 3 mb second the latter use one tag cable and two bus cables on the s 370 there is an option for a 3 0 mb s data streaming 36 channel with one bus cable and one tag cable the initial use for this was the 2305 fixed head disk which has 8 exposures alias addresses and rotational position sensing rps block multiplexer channels can operate as a selector channel to allow compatible attachment of legacy subsystems 37 basic hardware components edit a single width slt card many slt cards plugged into an slt board being uncertain of the reliability and availability of the then new monolithic integrated circuits ibm chose instead to design and manufacture its own custom hybrid integrated circuits these were built on 11 mm square ceramic substrates resistors were silk screened on and discrete glass encapsulated transistors and diodes were added the substrate was then covered with a metal lid or encapsulated in plastic to create a solid logic technology slt module a number of these slt modules were then flip chip mounted onto a small multi layer printed circuit slt card each card had one or two sockets on one edge that plugged onto pins on one of the computer s slt boards this was the reverse of how most other company s cards were mounted where the cards had pins or printed contact areas and plugged into sockets on the computer s boards up to twenty slt boards could be assembled side by side vertically and horizontally to form a logic gate several gates mounted together constituted a box shaped logic frame the outer gates were generally hinged along one vertical edge so they could be swung open to provide access to the fixed inner gates the larger machines could have more than one frame bolted together to produce the final unit such as a multi frame central processing unit cpu operating system software edit main article system 360 operating systems the smaller system 360 models used the basic operating system 360 bos 360 tape operating system tos 360 or disk operating system 360 dos 360 which evolved into dos vs dos vse vse af vse sp vse esa and then z vse the larger models used operating system 360 os 360 ibm developed several levels of os 360 with increasingly powerful features primary control program pcp multiprogramming with a fixed number of tasks mft and multiprogramming with a variable number of tasks mvt mvt took a long time to develop into a usable system and the less ambitious mft was widely used pcp was used on intermediate machines too small to run mft well and on larger machines before mft was available the final releases of os 360 included only mft and mvt for the system 370 and later machines mft evolved into os vs1 while mvt evolved into os vs2 svs single virtual storage then various versions of mvs multiple virtual storage culminating in the current z os when it announced the model 67 in august 1965 ibm also announced tss 360 time sharing system for delivery at the same time as the 67 tss 360 a response to multics was an ambitious project that included many advanced features it had performance problems was delayed canceled reinstated and finally canceled nb 6 again in 1971 customers migrated to cp 67 mts michigan terminal system tso time sharing option for os 360 or one of several other time sharing systems cp 67 the original virtual machine system was also known as cp cms cp 67 was developed outside the ibm mainstream at ibm s cambridge scientific center in cooperation with mit researchers cp cms eventually won wide acceptance and led to the development of vm 370 virtual machine which had a primary interactive sub operating system known as vm cms conversational monitoring system this evolved into today s z vm the model 20 offered a simplified and rarely used tape based system called tps tape processing system and dps disk processing system that provided support for the 2311 disk drive tps could run on a machine with 8 kb of memory dps required 12 kb which was pretty hefty for a model 20 many customers ran quite happily with 4 kb and cps card processing system with tps and dps the card reader was used to read the job control language cards that defined the stack of jobs to run and to read in transaction data such as customer payments the operating system was held on tape or disk and results could also be stored on the tapes or hard drives stacked job processing became an exciting possibility for the small but adventurous computer user a little known and little used suite of 80 column punched card utility programs known as basic programming support bps jocularly barely programming support a precursor of tos was available for smaller systems component names edit ibm created a new naming system for the new components created for system 360 although well known old names like ibm 1403 and ibm 1052 were retained in this new naming system components were given four digit numbers starting with 2 the second digit described the type of component as follows 20xx arithmetic processors for example the ibm 2030 which was the cpu for the ibm system 360 model 30 21xx power supplies and other equipment intimately associated with processors for example the ibm 2167 configuration unit 22xx visual output devices for example the ibm 2250 and ibm 2260 crt displays and the ibm 2203 line printer for the system 360 model 20 23xx direct access storage devices for example the ibm 2311 and ibm 2314 disk drives the ibm 2321 data cell main storage such as the ibm 2361 large capacity storage core storage large core storage or lcs and the ibm 2365 processor storage 24xx magnetic tape drives for example the ibm 2401 ibm 2405 and ibm 2415 25xx punched card handling equipment for example the ibm 2501 card reader ibm 2520 card punch ibm 2540 reader punch and ibm 2560 multi function card machine or mfcm 26xx paper tape handling equipment for example the ibm 2671 paper tape reader 27xx communications equipment for example the ibm 2701 ibm 2705 ibm 2741 interactive terminal and the ibm 2780 batch terminal 28xx channels and controllers for example the ibm 2821 control unit ibm 2841 and ibm 2844 29xx miscellaneous devices for example the ibm 2914 data channel switch and the ibm 2944 data channel repeater peripherals edit ibm developed a new family of peripheral equipment for system 360 carrying over a few from its older 1400 series interfaces were standardized allowing greater flexibility to mix and match processors controllers and peripherals than in the earlier product lines in addition system 360 computers could use certain peripherals that were originally developed for earlier computers these earlier peripherals used a different numbering system such as the ibm 1403 chain printer the 1403 an extremely reliable device that had already earned a reputation as a workhorse was sold as the 1403 n1 when adapted for the system 360 also available were optical character recognition ocr readers ibm 1287 and ibm 1288 which could read alpha numeric a n and numeric hand printed nhp nhw characters from cashier s rolls of tape to full legal size pages at the time this was done with very large optical logic readers software was too slow and expensive at that time models 65 and below sold with an ibm 1052 7 as the console typewriter the 360 85 with feature 5450 uses a display console that was not compatible with anything else in the line 38 39 the later 3066 console for the 370 165 and 370 168 use the same basic display design as the 360 85 the ibm system 360 models 91 and 195 use a graphical display similar to the ibm 2250 as their primary console additional operator consoles were also available certain high end machines could optionally be purchased with a 2250 graphical display costing upwards of us 100 000 smaller machines could use the less expensive 2260 display or later the 3270 direct access storage devices dasd edit further information direct access storage device ibm 2311 disk drive see also ibm s 360 and other ibm mainframe hdds the first disk drives for system 360 were ibm 2302s 40 60 65 and ibm 2311s 40 54 58 the first drum for system 360 was the ibm 7320 41 42 41 the 156 kb second 2302 was based on the earlier 1302 and was available as a model 3 with two 112 79 mb modules 40 60 or as a model 4 with four such modules 40 60 the 2311 with a removable 1316 disk pack was based on the ibm 1311 and had a theoretical capacity of 7 2 mb although actual capacity varied with record design 42 31 when used with a 360 20 the 1316 pack was formatted into fixed length 270 byte sectors giving a maximum capacity of 5 4mb in 1966 the first 2314s shipped this device had up to eight usable disk drives with an integral control unit there were nine drives but one was reserved as a spare each drive used a removable 2316 disk pack with a capacity of nearly 28 mb the disk packs for the 2311 and 2314 were physically large by today s standards e g the 1316 disk pack was about 14 in 36 cm in diameter and had six platters stacked on a central spindle the top and bottom outside platters did not store data data were recorded on the inner sides of the top and bottom platters and both sides of the inner platters providing 10 recording surfaces the 10 read write heads moved together across the surfaces of the platters which were formatted with 203 concentric tracks to reduce the amount of head movement seeking data was written in a virtual cylinder from inside top platter down to inside bottom platter these disks were not usually formatted with fixed sized sectors as are today s hard drives though this was done with cp cms rather most system 360 i o software could customize the length of the data record variable length records as was the case with magnetic tapes ibm 2314 disk drives and ibm 2540 card reader punch at the university of michigan some of the most powerful early system 360s used high speed head per track drum storage devices the 3 500 rpm 2301 43 which replaced the 7320 was part of the original system 360 announcement with a capacity of 4 mb the 303 8 kb second ibm 2303 40 74 76 was announced on january 31 1966 with a capacity of 3 913 mb these were the only drums announced for system 360 and system 370 and their niche was later filled by fixed head disks the 6 000 rpm 2305 appeared in 1970 with capacities of 5 mb 2305 1 or 11 mb 2305 2 per module 44 45 although these devices did not have large capacity their speed and transfer rates made them attractive for high performance needs a typical use was overlay linkage e g for os and application subroutines for program sections written to alternate in the same memory regions fixed head disks and drums were particularly effective as paging ...