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Special Systems Features Bulletin 

IBM 709Q and 7QS4 Data Processing Systems 

Additional Core Storage — RPO ED2120 (7090) or RFQ E15724 (7094) 

The Additional Core Storage feature for the IBM 7090-7094 Data Processing System pro- 
vides a secondlBM 7302 Core Storage, increasingthe capacity of main storage by 32,768 
words. The block of storage represented by both 7302 units is referred to as "main 
storage unit. " The two units are designated A and B, 

Internally, each computer operating cycle makes reference to only one of the main stor- 
age units. Additional core storage provides two methods of using main storage: (1) The 
65K mode — the computer program is enabled to address both of the main storage imits , 
and (2) the 32K mode — the computer program is able to address only one storage unit, 
so that main storage capacity available to that program is effectively 32,768 words. 
The first method is the normal one. The choice of method and single storage unit is 
made by two manual switches . 

STORAGE REFERENCE INDICATORS 

Internal selection of a main storage unit is directly controlled by certain indicators , 
whose settings are dependent upon programming. The indicators are: 

Instruction Cycle Control (ICC) ; Selects the main storage unit from which instructions 
are taken for computer program execution; the indicator functions in conjunction with 
the instruction counter in the Central Processing Unit (CPU). 

Execution Cycle Control (ECC) ; Selects the main storage unit whose locations are the 
subject of computer program arithmetic and logic operations ; the indicator functions 
in conjunction with the registers in the CPU that are normally involved in handling in- 
struction operands. 

Command Word Control (CWC) : One indicator per IBM 7607 Data Channel, Each 
selects the main storage unit from which channel command words are taken to direct the 
operations of a given data channel; each functions in conjunction with the channel loca- 
tion register of the respective data channel. 

Data Word Control (DWC) : One indicator per data channel. Each selects the main 
storage unit into which the respective channel causes data to be placed, or from which 
the chaimel causes data to be taken; each functions in conjunction with the channel address 
register of the respective data channel. 

Additional core storage does not affect the normal stepping of the instruction counter, 
channel location registers , or channel address registers , with the wrap-around con- 
tinuing to occur as they step from 77777 to 00000. However, the occurrence of a wrap- 
around in these counters does not affect the settings of the features storage indicators . 

The instructions that are part of additional core storage permit the computer program 
to interrogate settings of the ICC and ECC indicators, to change their settings, and to 

NOTE: Availability of this feature can be determined by requesting a price quotation from IBM. Consult 
IBM Region Sales Engineering Departments if additional information is required. 



© 1961 by International Business Machines Corporation 



transfer control of the computer from an instruction located in one storage unit to an 
instruction located in the other storage unit. Generally, the setting of the CWC and 
DWC indicators is determined by execution of the instructions that initiate data channel 
operation, or by a bit which programmers place in bit position 20 of channel commands. 

Settings of ICC and ECC indicators are not altered in the process of deriving the direct 
effective address of an instruction via indexing and/or indirect addressing. 

The current setting of the ECC indicator immediately determines the main storage unit 
from which a word is displayed when the display storage key on the IBM 7151 Console 
is pressed. 

Pressing the reset, clear, load cards, or load tape keys on the 7151 console causes the 
ICC and ECC indicators to be reset to an off condition (for reference to main storage 
unit A). 

MANUAL SWITCHES 

Two switches provided by the additional core storage and located on the IBM 7151 
Console are: 

Main Storage Capacity : This switch has a 65K position and a 32K position. 

Main Storage Unit : This switch has an A position and a B position. When the main 
storage capacity switch is in the 65 K position (normal), the computer program is 
enabled to address both main storage units. The main storage unit switch is then 
inoperative , 

When the main storage capacity switch is in the 32 K position, the setting of the main 
storage unit switch determines which 7302 unit the computer program is effectively able 
to address, by resetting the ICC and ECC indicators for the appropriate storage refer- 
ence and interlocking them against any subsequent attempts to alter those settings by 
programming. 

Clearing of storage, by pressing the clear key on the 7151 console, is affected by the 
setting of the main storage capacity switch. If that switch is in the 32K position, only 
the unit designated by the main storage unit switch is cleared on depression of the key. 
If that switch is in the 65K position, pressing the key causes both main storage units to 
be cleared. 

When the computer program is being run in the storage nullification mode , the settings 
of these switches have the following effect: 

1. With main storage capacity switch set to 65K, the upper half of both main 
storage units is protected against program references. 

2. With main storage capacity switch set to 32K, the upper half of the unit desig- 
nated by the setting of the main storage unit switch is protected against program refer- 
ences. The settings of these switches should be changed only when the computer is in 
manual status and all channel operations are completed. 



2 



INSTRUCTIONS 



TIA — Set ICC Indicator for Main Storage Unit A and Transfer 



+0101 



Y 



s, 1 



11 12-13 14 17 18-20 21 



Description ; The ICC indicator is set for reference to main storage unit A. The 
instruction counter is reset to location Y. The computer then executes the instruction 
stored in location Y of unit A. 

Indicators ; Instruction cycle control indicator set off. 
Timing; Two cycles. 

Execution; The direct effective address is computed, if necessary, before setting the 
ICC indicator. The setting of ICC is not changed if the main storage capacity switch is 
in the 32 K position, although an unconditional transfer is still effected. 

TIB ~ Set ICC Indicator for Main Storage Unit B and Transfer 




S, 1 11 12-13 14 17 18-20 21 35 



Description ; The ICC indicator is set for reference to main storage unit B. The 
instruction counter is reset to location Y. The computer then executes the instruction 
stored in location Y of unit B. 

Indicators ; Instruction cycle control indicator is set on. 
Timing; Two cycles. 

Execution ; The direct effective address is computed, if necessary, before setting the 
ICC indicator. The setting of ICC is not changed if the main storage capacity switch is 
in the 32K position, although an unconditional transfer is still effected. 

SEA — Set ECC Indicator for Main Storage Unit A 



-0761 



s, 1 



n 12 



00041 



17 18-20 21 



35 



Description; The ECC indicator is set for reference to main storage unit A. 



3 



Indicators; The ECC indicator is set off. 



Timing: Two cycles. 



Execution ; Since the address part of this instruction contains part of the operation 
code, modifications of the address (by an index register or otherwise) may change the 
operation itself. 

SEB — Set ECC Indicator for Main Storage Unit B 



-0761 



00042 



s, 1 



11 12 



17 18-20 21 



35 



Description; The ECC indicator is set for reference to main storage unit B. 
Indicators ; The ECC indicator is set on. 
Timing; Two cycles. 

Execution; Since the address part of this instruction contains part of the operation code, 
modification of the address (by an index register or otherwise) may change the opera- 
tion itself. 

IFT — Instruction Cycle Control Indicator, bff Test 



-0761 



00043 



s, 1 



11 12 



17 18-20 21 



35 



Description ; If the ICC indicator is in the on condition, the computer proceeds to the 
next sequential instruction. If ICC is off, the computer skips the next instruction and 
proceeds to the one after it. 

Indicators ; None . 

Timing; Two cycles. 

Execution; Since the address part of this instruction contains part of the operation code , 
address modification may change the operation itself. 



EFT — Execution Cycle Control Indicator, Off Test 



-0761 



s, 1 



11 12 



00044 



17 18-20 21 



35 



Description ; If the ECC indicator is in the on condition, the computer proceeds to the 
next sequential instruction. If ECC is off, the computer skips the next instruction and 
proceeds to the one after it. 

Indicators ; None . 

Timing; Two cycles. 

Execution: Since the address part of this instruction contains part of the operation code , 
address modification may change the operation itself. 

Note: A 7090 cycle equals 2:18 microseconds; a 7094 cycle equals 2 microseconds. 
EFFECT ON COMPUTER TRAP OPERATIONS 

The operation of computer traps as described in the IBM 7090 Data Processing System 
Reference Manual , Form A22-6528, or IBM 7094 Data Processing System Reference 
Manual , Form A22-6703, is affected as follows: 

If the main storage capacity switch is set to the 32K position, the additional core storage 
introduces no changes with respect to trap operation. Main storage unit selection is 
then determined by the main storage unit switch, which is set to refer to the unit in 
which trap routines and the rest of the program have been loaded. 

If the main storage capacity switch is set to the 65K position, the additional core storage 
introduces some changes. Upon the occurrence of a trap of any type, the contents of 
the instruction and execution cycle control indicators are stored respectively in bit 
positions 3 and 4 of the usual trap location (the one in which the contents of the instruc- 
tion counter are stored): then the ECC and ICC indicators are set off and a transfer to 
a trap routine in main storage unit A is effected, hi the case of a data channel trap, 
however, there may be an immediate return to the main program. If the instruction 
following the trap location (the next instruction to be executed) is an unconditional trans- 
fer, or a conditional transfer with conditions met (or an execute instruction addressed 
to such a transfer instruction) , the ICC and ECC indicators are automatically reset off 
for reference to main storage unit A, and execution of the trap routine continues. 
However, if the instruction following the data channel trap location is different from 
that just discussed, the program resumes from the point at which the trap occurred, 
with the settings of the ICC and ECC indicators remaining the same as before the trap. 

While the computer program is running in the transfer trap mode, the TIA and TIB 
instructions, like other of the unconditional transfer tjqje instructions, cause the com- 
puter to be trapped each time one of them is executed. However, the TIA and TEB 
instructions in this instance do not alter the setting of the ICC indicator, so that the 
existing setting is stored in the transfer trap location. 

Note: On all traps that occur during operation in the 65K mode, the decrement portion 
of the store location is cleared and bit positions 3 and 4 will contain the condition of the 
ICC and ECC indicators. 



5 



SELECTION OF MAIN STORAGE UNITS 



Main storage unit selection is determined by settings of the ICC and ECC indicators. 

The ICC indicator is set to the off condition, for reference to main storage unit A, in 
the following ways: 

1. Depression of the reset, clear, or load keys on the 7151 console. 

2 . Placing the main storage capacity switch and the main storage unit switch in the 
32 K and A positions, respectively. 

3. Execution of the TIA instruction with the main storage capacity switch in the 65K 
position. 

4. Execution of a trap routine with the main storage capacity switch in the 65K 
position. Re-entry of main program from the trap routine may restore the opposite 
setting, however. 

The ICC indicator is set to the on condition, for reference to main storage unit B, in 
the following ways: 

1. Placing the two switches in the 32K position and the B position, respectively. 

2. Execution of a TIB instruction with the main storage capacity switch in the 65K 
position. 

The ECC indicator is set to the off condition, for reference to main storage unit A, in 
the following ways: 

1. Depression of the reset, clear, or load keys on the 7151 console. 

2. Placing the two switches in the 32 K position and A position, respectively. 

3. Execution of a SEA instruction with the main storage capacity switch in the 
65 K position. 

4. Execution of a trap routine with the main storage capacity switch in the 65 K 
position. Re-entry of main program from the trap routine may restore the opposite 
setting, however. 

The ECC indicator is set to the on condition, for reference to main storage unit B in 
the following ways : 

1. Placing the two switches in the 32 K position and the B position, respectively. 

2. Execution of a SEB instruction with the main storage capacity switch in the 
65K position. 

EFFECT ON 7607 DATA CHANNEL OPERATIONS 

Two indicators have been placed in each IBM 7607 Data Channel in a computer system on 
which the additional core storage is installed. One of the indicators is command word 
control indicator (CWC) , which functions in conjunction with the channel location register. 
The other indicator is the data word control indicator (DWC) , which functions in con- 
junction with the channel address register. The CWC indicator determines from which 



6 



main storage unit channel commands are currently to be taken for operation of the given 
data channel. The DWC indicator determines the main storage unit into which the given 
data channel currently may place data, or from which it may take data. When these 
indicators are in an off condition, they refer to main storage unit A; in an on condition, 
they refer to main storage unit B. 

The CWC in a data channel is set in two ways. First, it is set to the same condition as 
the execution cycle control (ECC) indicator at the time a load channel or reset and load 
channel instruction addressed to the respective data channel is executed. Second, it is 
set again each time a transfer in channel (TCH) command is encountered in the sub- 
program for that data channel, to the condition indicated by bit position 20 of the trans- 
fer command itself or by bit position 20 of the location the TCH indirectly addresses. 
The programmer places a 1 in position 20 to indicate reference to unit B. A CWC 
indicator is reset to the, off condition upon the execution of a read select or write select 
instruction addressed to the respective data channel. 

The DWC indicator in a data channel is set to the condition of bit position 20 of every 
command (or bit position 20 of a location indirectly addressed by a command) in the 
subprogram for that data channel, except transfer in channel commands. Again, the 
programmer places a 1 in bit position 20 of a command to indicate reference to main 
storage unit B; a 0, to indicate reference to unit A. A DWC indicator is reset off upon 
execution of any of the following instructions addressed to the respective data channel; 
read select, write select, load channel, reset and load channel. 

Depression of reset, clear, load cards, or load tape keys on the 7151 console causes 
all CWC and DWC indicators to be reset to off (for reference to main storage unit A). 

Depression of the channel reset key on a given 7607 data channel, while that unit is in 
manual status, causes the CWC and DWC indicators in that particular data channel only 
to be reset to off. 

Each of the store channel instructions is expanded to record the condition of a data 
channel's CWC indicator in bit position 18 of the location addressed by the instruction, 
and the condition of the DWC indicator to be recorded in bit position 20. When one of 
these indicators in on, a one is stored in the appropriate bit position: for an off con- 
dition, a zero is stored. 

Wrap-around on a channel location register or channel address register occurs as it 
steps from 77777 to 00000, and does not affect settings of the DWC or CWC indicators. 

EFFECT ON 7909 DATA CHANNEL OPERATIONS 

Two indicators are added to each IBM 7909 Data Channel in a computer system on which 
the additional core storage is installed. One indicator, the command v/ord control (CWC) 
indicator, works with the channel's command word counter and determines from which 
main storage unit the channel commands are currently to be taken for operation of the 
given data channel. The other indicator, the data word control (DWC) indicator, works 
with the channel's address counter and determines the main storage unit to or from 
which the data channel may reference data. When these indicators are off, they 



7 



reference main storage unit A; in an on condition, they reference main storage unit B. 
(When the main storage capacity switch is in the 32K position, the indicators are held 
reset. 

The CWC indicator for a given channel is set in two ways. First, it is set to the same 
condition as the ECC indicator at the time a reset and start channel instruction addressed 
to the respective data channel is executed. Second, it is set again, each time a transfer 
in channel (TCH) command is encountered in the subprogram for that data channel, to the 
status of bit position 20 of the transfer command itself or by bit position 20 of the location 
that the TCH indirectly addresses. The programmer places a 1 in position 20 to indicate 
reference to main storage unit B. 

The DWC indicator in the data channel is set to the condition of bit position 20 of every 
command (or bit position 20 of a location indirectly addressed by a command) , although 
in certain commands, such as TCH, LCC, ICC, SMS, and LIP, the indicator performs 
no logic. Again, a 1 in position 20 indicates reference to main storage unit B. 

The CWC indicator is reset by the execution of reset channel and reset and start channel 
instructions addressed to the respective data channel. The DWC indicator is reset in the 
same manner, with an additional reset caused by the absence of a bit in position 20 of a 
command to be executed by the channel. 

Depression of reset, clear, load cards, or load tape keys on the 7151 Console causes all 
CWC and DWC indicators to be reset off (for reference to main storage unit A). 

Depression of the channel reset key on a given 7909 Data Channel, while that unit is in 
manual status, causes the CWC and DWC indicators in that particular data channel only 
to be reset off. 

The store channel instruction is expanded to record the condition of a data channel's CWC 
indicator in bit position 18 of the location addressed by the instruction and the condition 
of the DWC indicator in bit position 20. When one of these indicators is on, a 1 is stored 
in the appropriate location. 

On a channel interrupt, only the status of the CWC indicator is stored, being placed in bit 
position 20 of the channel's interrupt location. Again, a 1 is stored to indicate an "on" 
status of the CWC indicator 

Wrap-around on a channel command counter or channel address register occurs during 
stepping from 77777 to 00000 and does not affect settings of the DWC or CWC indicators. 

GENERAL PROGRAMMING CONSIDERATIONS 

The location addressed by execute instructions will be in the main storage unit, referenced 
by the current setting of the ICC indicator. 

Note that indirect addressing of channel commands requires that consideration be given 
the contents of bit position 20. In this case, bit position 20 of the command is used to 
identify the main storage unit containing the location directly addressed by the command. 



while bit position 20 of that location is used to condition the CWC (if the command is a 
TCH) or the DWC (for any other command). 



In the execution of indirectly addressed computer instructions, the ICC indicator deter- 
mines main storage unit selection throughout the process of effective address calcula- 
tion, internally. For an instruction with an operand (like CLA) the ECC indicator then, 
just as in the case of instructions not indirectly addressed, determines selection of the 
main storage unit from which the operand is obtained. 

It is extremely important that the two switches are always set to the positions required 
by the particular computer program being run, or about to be run, on the computer. Use 
of several of the instructions provided by the additional core storage makes it possible 
for a housekeeping routine or restart program to interrogate the setting of the manual 
switches, so that the console operator can be notified if the settings should be changed 
or restored to those required for that program. Following is a suggested procedure to 
determine the switch settings: 

Instruction Comment 

SEB Set ECC for reference to main storage unit B 

EFT Test resultant setting of ECC indicator 

TRA ECC indicator is in on condition; transfer to SEA 



It is also important that initial settings of the ICC and ECC indicators are appropriate 
for each program to be run. There is at least one set of circumstances that may re- 
quire special provisions for controlling the initial settings. If independent programs 
are batched on a systems tape for a continuous series of computer runs (with no inter- 
vening console -initiated operations) and those programs are to include some written for 
the additional core storage as well as some neither written nor modified for this feature, 
either the programs written for the additional core storage must in their end-of-job 
routines restore the ICC and ECC indicators to an off condition, or the monitor pro- 
gram supervising the series of runs must restore those indicators after each run. 



SEA 
EFT 
TRA 



TRA 



TRA 



instruction (below) 

SEB did not reset the indicator; main storage capacity 
switch is in the 32 K position and the main storage unit 
switch is in the A position. 

Set ECC indicator for reference to main storage unit A 

Test resultant setting of ECC indicator 

The SEA did not reset the indicator; main storage capacity 
switch is in the 32 K position and the main storage 
unit switch is in the B position. 

The main storage capacity switch is in the 65 K position. 
If the 65 K position is the correct one, the position of the 
other switch is of no consequence (since it is then inop- 
erative). If the 65K position is the incorrect one, cause 
the switch to be set manually to the 32K position and 
repeat the entire procedure to see if the main storage 
unit switch is set properly. 



9 



Trap locations must always be in main storage unit A. This may require programming 
of transfer trap routines to provide for the case where the transfer instruction causing 
a transfer trap is located in main storage unit B. It is necessary to leave the transfer 
trap mode in order to re-enter the main program located in main storage unit B from 
the trap routine located in unit A. 

With transfer traps, the condition of the ICC and ECC indicators is stored at the trap 
location (only when the main storage capacity switch is in the 65K position). 

The additional core storage should not interfere with the running of programs not writ- 
ten or modified for this feature, provided that such programs make no use of bit posi- 
tion 20 of channel commands or of the operation codes assigned to the new computer 
instructions provided by additional core storage. If the program is to be run with the 
main storage capacity switch in the 65K position, there may be conflicting use of the 
decrement portion of the transfer trap location. (See "Effect on Computer Trap 
Operation" section.) In that event, however, the program could be run with that switch 
in the 32K position to circumvent the conflict. 



PHYSICAL PLANNING INFORMATION 



SYSTEM LAYOUT 

Three configurations are possible in a system that is to have the Additional Core Stor- 
age feature installed. The configuration a customer is to have depends on the customer's 
32K system and the type of core storage unit to be added. In the figures and tables, 
7302A is used to designate the air-cooled units. 

The three configurations are: 

A Two oil-cooled core storage units 

B One oil-cooled and one air-cooled core storage unit 

C Two air-cooled core storage units 

Configuration A, Oil/Oil 

In this configuration, the units must be placed as shown in Figure 1. 



67 AND 69 





68 

r n V ' 




7108 


7109 


7606 


7302 
NORMAL 


7302 
ADDED 



Figure 1. Oil/ Oil Configuration 



In this system, the two storage units are butted together and the signal cables are, of 
fixed length and need not be specified with the feature order. 

Configuration B , Oil/Air 

In this configuration, the units are placed as shown in Figure 2. 



73 02 A 
(ADDED) 



72 AND 70 If ^ i i 



7108 


7109 


7606 


7302 








(NORMAL) 



Figure 2, Oil/Air Configuration 

In this system, the normal 7302 will be an oil-cooled 7302 and will be adjacent to the 
7606 Multiplexor. The added 7302 may be placed as the physical planner sees fit within 
the cable length restrictions noted in Cable Chart B. (Normal system cables are not 
shown. ) 



Configuration C, Air /Air 

In this configuration the units must be placed as shown in Figure 3. 



7302A 
NORMAL 



7302A 
ADDED 



XT" 



72 AND 70 




Figure 3. Air/ Air Configuration 

In this system, the normal 7302 would be an air-cooled unit and would be placed within 
the cable restrictions of a normal 32K system. 

The added 7302 may be placed as the physical planner desires within the cable length 
restrictions noted in Cable Chart C. (Normal system cables are not shown.) 

All other new cables to be added to the system are shown in Figure 4 and listed on 
Chart D. 




SOUID WHEN 7607 
DOTTED WHEN 7909 



Figure 4. Cables Added to System 



Cable Chart B Oil/ Air 



Cable Group 
70 

71 a,b 

72 a 



IBM P/N 

587314 
587314 
587314 



Description 

7606 to 7302 
7302 to 7302A 
7606 to 7302A 



Diameter 
(inches) 

.93 
.93 
.93 



Max. 

length (ft) 

40 
40 
40 



Y Z 
Dimension 
inches 



60 
60 
60 



12 
12 
12 



Note 

I 
I 
I 



I. Included in additional core storage rental. Use dimensions shown to determine total length, and order with 
the additional core storage. 

Cable Chart C Air /Air 



Cable Group IBM P/N Description 



Diameter 
(inches) 



Max. 

length (ft) 



Y Z 
Dimension 
inches 



Note 



70 

71 a,b 

72 a 



587314 7606 to 7302A .93 

587314 7302A to 7302A .93 

587314 7606 to 7302A .93 



40 
40 
40 



60 
12 
60 



12 
12 
12 



I. Included in additional core storage rental. Use dimensions shown to determine total length, and order with 
the additional core storage. 

Cable Chart D System Cables 
(Exclusive of 7302 Signal) 

Y z 

Diameter Max. Dimension 



Cable Group 


IBM P/N 


Description 


(inches) 


length (ft) 


inches 




Note 


A 


532542 


400 cycle to 
















7302 


.70 


75 


11 


70 


I 


A 


532554 


60 cycle to 
















7302 


1.20 


75 


11 


67 


I 


A 


532537 


7302 heater 
















input 




75 


9 


162 


I, IV 


B 


5303620 


7151 to 7618 


.50 


75 


11 


12 


II, III, rv 


C 


587314 


7606 to 7607 #1 


.93 




50 


55 


II, ni 


D 


587314 


7606 to 7607 #5 


.93 




53 


55 


II, III 


E 


587314 


7607 to 7607 


.93 




57 


55 


II 


J 


5330620 


7606 to 7909 


.93 




50 


24 


V 


K 


5330620 


7607 to 7909 


.93 




57 


24 


V 


L 


5330620 


7909 to 7607 


.93 




24 


55 


V 


M 


5330621 


7909 to 7909 


.93 




24 


24 


V 


N 


5330620 


7606 to 7909 


.93 




57 


24 


V 



I. Not included in additional core storage feature rental and must be ordered separately with 7302, Use 
dimensions shown to determine total length. 

II, Included in additional core storage rental. Use dimensions shown to determine total length. (Refer to 
IBM 7090 Data Processing System Physical Planning Installation Manual, Form X22-1209-1. ) 

III. The 7606 can have two sets of signal cables to feed data channels. Maximum of four data channels may be 
connected to each set. Maximum length of this signal cable from the 7606 to the data channel is 100 feet with 
one data chaimel per set. This length is reduced by 20 feet each for the addition of the next two data channels 
and 28, 1/2 feet for the third data channel added to each set. 



rV, This cable not required for configurations B and C. 

V. Included in 7909 Data Channel 65K systems special feature rental. Use dimensions shown to determine total 
length, and order with the feature order. (Refer to IBM 7090 Data Processing System Physical Planning Installa- 
tion Manual . Form X22-1209-1. ) 



mm 

® 

International Business Machines Corporation 

Data Processing Division, 112 East Post Roati, White Plains, N. Y. Printed in U.S.A. L22-6636-1 4/63