IBM SYSTEM/360 READ ONLY STORAGE

[Music] spe today I would like to discuss with you some of the advantages and functions of readon storage as it is utilized in system 360 first of all I think we need to look at the two primary purposes or reasons for readon storage number one all systems require a control function in order to make the data flow through the system on a balanced operation to give us the best price performance and readon storage now replaces the conventional uh tubes SMS cards various other types of circuitry that we've utilized in the past number two it gives us compatibility control with proven object programs of the 147,000 series systems so that we can ease the transition from currently installed 147,000 to system 360 I think you should note that the model 70 uses conventional circuits for the control of its Central processor unit and uh Associated equipment due to the speeds involved uh at that level of machine now by way of illustration we will use an example of the readon storage that we find in the model 30 and in this I simply want to say that the read only storage replaces all types of tubes wiring resistors capacitors Etc and puts in a non write non-destructive readon memory this is not available to the application programmer you yourself for instance it is utilized only by the engineer who is actually developing the internal program for the machine we'll introduce a few terms such as microinstruction microprogramming and as we go through the explanation I think this will all become clear to you now first of all in the control of a system we are concerned with five elements input of data output of data storage for the containing of intermediate results of data and the application program and the programming systems whatever may be resident there the central processor unit with with its arithmetic and logical units and of course the Control Function which ties all of these together and maintains a smooth flow of data through the system now by way of illustration of the program cards that are used in this uh machine system this is a standard 80 column size card it has 12 microw wordss corresponding to the 12 horizontal rows that you normally find on the card of 12 through zero digit values it has a series of capacitive plates on here such that this can form when it's put in the Cent plate what we call the card capacitor readon storage until such time that an engineer determines that a pattern of these little plates needs to be punched out I would look at this just as you would look at a coding sheet for a program as my blank program card the micro instruction involved in this is the internal instruction that the machine will use for decoding the ad or the move or the read or the write instruction that you give it in your application program internally the machine looks at that instruction say an ad instruction as a macro instruction and then it goes into a micro level or several individual steps of instructions such that we can now make the machine move the data through this machine develop the desired results and put the answer or the results in the specified locations any single instruction may require one or more of these micro instruction levels it's strictly dependent on the complexity of the operation that you're trying to perform in the case of the model 30 the engineer determines a bit pattern for each micro instruction word and these bit patterns are sensed and sent out through this sense board into the machine such that they will cause various circuits to gate open or close to allow the transition of data or the movement of data through the machine readon storage also takes care of the problem of getting timed impulses through the proper circuits at the proper time under control of the bit pattern now just as in normal core storage which is a non-destruct which is a destructive type of readout storage we have a parody associated with each micro instruction so that every time we read a bit pattern out of here we know that the machine will function in a reliable and valid fashion now to form a readon capacitive storage device in here we have established between the sense board and this program card a series of capacitors each of the little squares that you see detailed on here forms one plate of a capacitor and anytime you take two plates put them close together and apply a voltage across them you can develop a capacitive pulse if we have a pulse there we say that we have a bit or a one condition if I perforate one of the plates or remove it then I say I have a no bit or a noap passive pulse consequently we are able to develop the 01 uh binary bit pattern required for the machine operation the engineer determines what pattern he needs at a particular sequence in time of the machine operation and sets this up in the cards that then becomes a permanent readon storage that the machine will constantly utilize and it remains fixed until such time that the engineer comes along and says he has to change it or modify it to improve some operation or to change the method of operation or to add a feature to the system now for a moment I'd like to illustrate to you some of the other read only storage devices that are used in the model 40 the 50 the 60 and the 62 to contain the micro instruction here again you see an example of the model 30 readon storage micro instruction program card that the engineer develops and you can see here a bit pattern as indicated by the white uh background at the proper time each word is accessed into the encoding and decoding circuits and then the timed impulses are sent out to gate the machine in the case of the model 40 which was developed in herley England the engineers were going to develop a readon storage device but they were told that the only Prime criteria that they had to follow were two things one all programs had to be functionally compatible so that we could have upward and downward capability for the instruction sets of system 360 and we could take a program for the model 40 and run it equally well on the 30 or equally well on the 50 getting the same valid results in the case of the model 40 the engineers developed what we call a Transformer readon storage I'm sure most of you are familiar with transformer action you induce a current in a primary coil this develops a field around the coil and if you have a core running through that you can then develop a secondary pulse in a secondary winding and here again if we have the presence of a transformer pulse we have a one bit if we don't have the impulse then we have a zero bit so we have again the 01 binary bit pattern required in the case of the model 40 a micro instruction word is comprised of 60 bit positions the outside row forms one word the inside row forms another word so each of the tapes in a model 40 has two microw wordss each of the cards in a model 30 has 12 micro wordss in the case of the model 50 60 and 62 due to the speed circuits involved and the complexity of the circuits they went to still another type of readon storage media and this is an edge plate with again a similar uh electrical phenomena as used in the 30 a capacitive effect and now the bit sizes for each of the word varies depending on whether you're talking about a Model 50 or 6062 and the number of words will vary depending on again the uh work that you wish to accomplish within the machine circuits so the three different types of readon storage all accomplish the same function the control of the system 360 processing system that you would have in any one installation it also is consistent in that all 50s have the same pattern of readon storage all 40s have the same pattern and all 30s have the same pattern as again do the model 60s and 62s all right from the readon storage control then I would like to Simply go through a very simple example of add a to B and store the result and C with a representative data flow and a representative example of microprogrammed instruction it's very basic but I think it will help give you a better understanding of readon storage in the chart that we have here on the wall we'll say that this will represent the data flow of a system in that we have main storage we have a storage address register so that we can all uh control the point or location within storage that we're accessing we'll have various registers in here that will store data and hold them intermediate we'll have an A and A B register or an X and Y register or a p and Q register whatever terminology wish to use associated with the arithmetic and logical unit and of course we'll have a sum register in this case to get our results back into main storage now a very simple basic data flow but how are we going to control it we take a look we can say that this might be a representative micro instruction routine to handle the simple single instruction that is an application programmer you would write for system 360 and that is let's say add a to B and store the result in C and I've used basically the illustration of the model 30 micro uh programming under our readon storage address control register again we need to know at all times exactly where our next instructions coming from so we can sequence through a fixed routine or under certain conditional branches we can leave a routine and go to some other micro instructions so we have the same type of programming flexibility from the engineering side that you have in your application program for handling your data let's say that at0 Z we will start out with step number one we just accessed a new instruction from core store storage and we are starting to decode it our micro instruction at this time tells us that we want to read a field out of storage in order to do that we've got to either close or open certain gates in this case we send out a timed impulse which is going to take us up to gate one and close that and then as our sensing pulses come through storage at the proper point we will transfer the data field a into the storage register at the completion of this mro level instruction we then advance to the next sequence instruction under control of R uh address register and we see that the next signal or instruction we get is to regenerate the a field remember we came out of a destructive readout device so in this case then we close gate a and send timed impulses representing the data that we just took out of core storage and send it back to its original location then the next next thing that we want to do on the next logical sequence of instruction is to store a field in which case again we've got to close another data path so gate number two is closed and we put this into a hold register the readon storage control then advances to the next sequential instruction which says in this case read the B field so again under control of the timed impuls is coming out we're going to close gate number one come out here to the main storage and take the B field in it will hold there because there's no other place for it to go again under read only storage address control register it says go to the next sequential instruction and there we see a multiple function being carried out on this single instruction step and that in this case is simply adding a to B so we had the a field held here we had the B field in here so to execute this we will close Gates three and five moving the a field here the B field here and since we are now tied directly to the arithmetic logical unit the rest of the function of uh uh the arithmetic operation is carried out directly developing the sum and leaving the result in the arithmetic and logical unit then the next micro instruction uh says that we want to store the sum in this case then again we must close another data path and as you can see by by our time sequence here we will come out and close gate number four at which time the sum comes over here now we want to take the sum into main storage we could just as well say store this register in this particular case we'll use the term regenerate the sum into core storage and this is simply to illustrate that we're going to use a common data path that we had used previously for the a field so we will take the value which is a result C bring it out and put it in its appropriate location under control of the storage address register that's a very basic example of how readon storage functions but I believe that it gives you the idea that all of the data flowing through the system has to go through under a sequenc and properly timed control and we do that with readon storage now this points out the fact that it is and can be extremely flexible so that for any conditions that you would have the engineer can come along and handle overflows underflows he can handle balance U rather compare equal high low and select the appropriate internal control to Branch to uh the next course of action now that pretty much addresses readon storage as we see it within the system in the case of the model 30 with this device several of these sense plates would be in the machine such that the unit is actually approximately this wide it has approximately 4,000 words of readon storage used that takes care of the 360 instruction set or what we call the native 360 mode of operation so anytime I have object code for the 360 I would use this readon storage device now that is true if I'm talking about a model 40 I would have a readon storage unit in this case it would be the Transformer readon storage type of unit if it were a Model 50 60 or 62 it would be the other type of read only storage as we see indicated here that is the balance capacitor type now let's get to the second major advantage of read only storage and that is the compatibility feature and capability that it allows us to run a machine in compatibility mode we would in effect set aside the normal readon storage with a 360 instruction set that's fixed the engineer determines of that and it stays that way from time uh here on out until such time that he generates a change the application programmer never can affect that now I'm uh I have a model 30 or model 40 or 50 or 60 and I have a certain machine that I want to run in what we call the compatibility mode I will specify that feature on my system and then in addition to the readon storage which contains the 360 instruction set I will get another unit that will be added to the machine so we'll assume the 360 read only storage is here and this is a new one now the only difference between the original readon storage in this one is that the code that is generated in this readon storage does not interpret 360 instructions it now interprets 1401 instructions or 1460 or 1410 or any of the 7,000 series that we run under the compatibility mode in which case then we're saying that for compatibility operation I would use this type of readon storage for instance in the model 30 I would go through the same type of operation but the commonness in here now comes back to the fact that I use the 360 data flow paths I don't add new data flows I don't put in a 1401 internal circuit I make the 360 look like a 1401 for instance but I do put in a new readon storage so that I can properly sequence and control the flow of data through the system all right in the case of each of the models that we're talking about we must then have uh some readon storage if we are going to use readon storage and what we call the compatibility mode now I would like to go on to a few definitions and then give you some significant advantages of system 360 and readon storage Again by way of very brief summary the primary purpose is the control of a system in this case any of the models 30 through 62 secondly it does allow us to interpret an instruction set for another machine and as we have specified those that have been announced as compatibility features [Applause] I think one of the most difficult things that in the marketplace that you have is a handling of the terms that you will run into compatibility as we look at it normally means that the instruction set let's say for 1401 on the model 30 is comprised of All readon Storage with a micro programmed instruction as we talked about and additional SLT circuits no program support is normally involved with that that is a hardware compatibility feature the second term we run into although you will find it listed in your sales manual as a compatibility feature is the term emulation and that means that we will use from very much readon storage to relatively little readon storage from very much SLT additional circuits to very few additional SLT circuit circuits and to simple input output programming support to very significant comprehensive programming support packages and in the case of pure simulation that's a term that you're all familiar with because we've had it since the age of computers and that is that we will interpret any instruction set from another machine and try and make the host machine act as though it were that foreign machine and that is all done by interpretive routines um in software only now I think the next thing that we would like to discuss are the advantages of readon storage primarily readon storage allows a full instruction set for the models 30 to 62 so that you can have true upward and downward program compatibility of your programs and also it says that regardless of what model I am on I have one set of instructions to learn and I'm going to use one set of programming support it provides the best system price performance because now we find that through the use of readon storage and the different types that I've indicated here we are able to allow a full instruction set performance on a small machine which is balanced to its throughput performance as well as allowing a very comprehensive in hensive system like the model 6062 with its full instruction set identical to the 30 match to its throughput performance one logical design of system 360 through readon storage control this basically is a way that we obtained the one logical design although we actually have six physical systems involved it's the key to program compatibility upward and downward as I've pointed out a very necessary PR requisite for expanding and shrinking workload situations then the second I think most important advantage that I've highlighted already is that it does provide compatibility with proven object programs of the 147,000 series as specified on the compatibility features that have been announced each microprogram instruction has parody to validate the read only operation and again let me point out this is readon nobody can write into this memory seven it will definitely facilitate field engineering improvements when I say field engineering improvements the product department or division develops the engineering updating of the machine and it must be installed by the field engineering due to the flexibility of readon storage the relative ease of replacing sections of it we are able to generally speed up the uh engineering Improvement of a system with a greater reliability it reduces the CPU requirement for the control function of the computer and in some cases has reduced it as much as 4 to one all right at this time I would like to show you a series of slides which will give you again a somewhat uh detail summary or brief summary of what I have discussed and also will illustrate how some of these devices are physically located within the equipment here we see an example of system 360 circuits as we might have it with conventional control for instance in the model 70 the local store which contains various registers your arithmetic registers the ALU unit and the shifter now all of these units have to be gated and control so that data will flow through them properly and at the uh correct time we do that with timed circuit impulses over here with uh logic control as we see it associated in these units now in the case of the model 70 this is extensive SLT uh circuitry but in the case of the smaller systems the same type of control in order to give us this control over the uh data flow and to handle the instruction set would put us out of proper bounds as far as a good price performance so then we go to read only storage The Logical function is still there in that we still must gate the registers and control the data flow but we have simply replaced all of the SLT circuits with smaller or lesser amount of SLT and readon storage units with the permanently microprogrammed instruction set here again we see an exploded view of the type of microprogram card capacitor read only storage as is found in the uh Model 30 this unit happens to be the sense board this is an example of the microprogram card itself here is a view of a full module of read only storage for the model 30 it happens to represent uh approximately 4,000 words and here you see a separate microprogram card you can see the ease in the case of the model 30 of inserting microprogram cards or changing microprogram instructions it's very necessary of course that you recognize that each set of uh micro instructions have a a very finite and fixed sequence relationship to the total program and as such nobody but the qualified and designated field engineer should be doing any manipulation of these CS here you see it actually mounted within the uh CPU of the model 30 it's not a very large unit relatively small here again pointing up the uh CPU size reduction that I addressed earlier in some cases as much as 4:1 this is an example again of the uh Transformer read only storage micro instruction uh myar tape and here again if you look closely you can see the circuit lines that come down and the little perforations in here which tell us that a current will go around a core or will bypass a core thereby developing the bit no bit condition this as I said has two micro words uh for the readon storage instruction set here's a little bit better view of an individual micro instruction tape here is the type of core that is inserted through several of these tapes in a complete assembly as we see uh this set of tapes fanned out uh from this unit all of the tapes have contacts that are plugged in down here and then they go into the logic circuits and tie into the rest of the data flow of the system this is an example of the uh bit plane for the balance capacitor read on only store that we find in the case of the models 50 60 and 62 they all use basically the same type of storage again as I said the word size varies depending on what model we're talking about but you can see the way that the field engineer can change a bit plane uh in these units this is known as a spider and that's used to press all of the bit planes in a particular unit of readon storage together so that all elements of the uh micro instruction word in there that is all the capactive elements maintain the same electrical phenomena uh capacitance value here is a picture of the thing is it might fit in there after the engineer has actually inserted it onto the location pins here is a standoff view in the case this particular case of a model f where you can see all of the readon storage involved this is only a couple of thousand words but as I explained to you the bit planes that are used have uh very large microword instructions involved in it the elements that you see down here are the large circuit boards where SLT circuits are involved this is an exploded view or back off view of the model 60 and in this case the readon storage happens to be be located in this part of the CPU somewhat different as far as its physical location uh between the model 50 and the model 60 but its function is identical uh to the model 50 that is to handle the interpretation of 360 instruction set by way of summary these are the announced compatibility features I should mention at this time that we have since announced the 1620 emulator to go on to the model 30 in the case of the model 30 until recent announcement of the program mode switch all of the model 30 emulators were what we call True Hardware compatibility features in the case of the model 40 we are in the ulation mode as we are with the 50s and the 60s and 60 uh 2 systems I trust that these slides and the other presentations in here have served to illustrate to you the function and better defined readon storage as it is utilized in system 360 thank you very much a member of the audience has been given the responsibility for answering any questions you may have regarding this presentation