machine check recording mode
SECTION 10: ARCHITECTURE AND SYSTEM COMPONENTS
10:05 ARCHITECTURE DESIGN
The basic design objectives embodied in System/310 Model 165
architecture provide System/360 Model 65 and 15 users and 1000-series emulator users with a growth system that incorporates improvements and additions to System/360 architecture. The Model 165 provides new system capabilities, performance improvements, and features to increase system reliability, availability, and serviceability. This has been achieved under the following conditions:
• System/310 Model 165 architecture is upward compatible with that of System/360 models so that most user programs written for System/360 will run efficiently on the Model 165 without modification.
• Programming systems support for the Model 165 is based on that provided for System/360 models, namely on OS MFT and MVT.
• Most currently announced System/360 I/O devices will operate on the Model 165. (See Section 20:05 for a list of the I/O devices that cannot be included in a Model 165 configuration.)
• The open-ended design characteristic of System/360 has been preserved and extended in System/370.
As a result of the architecture design criteria used for this new system, all programs written for System/360 (Models 25 and up) will operate on a System/310 Model 165 with a comparable hardware
configuration, with the following exceptions:
1. Time-dependent programs
2. Programs using machine-dependent data such as that which is logged in the machine-dependent logout area. (OS SER and MeB and DOS MCRR error-logging routines for System/360 models will not execute correctly.)
3. Programs that use the ASCII mode bit in the PSW
4. Programs that depend on the nonusable lower processor storage area being smaller than 1512 bytes. This area can be reduced to 512 bytes by moving the CPU logout area. (See Section 50.) 5. Programs deliberately written to cause certain program checks 6. Programs that depend on devices or architecture not implemented
in the Model 165, for example, the native file of the Model 44, relocation implemented in the Model 61, etc.
7. Programs that use model-dependent operations of the System/370 Model 165 that are not necessarily compatible with the same operations on System/360 models
Note that these are the same types of restrictions that exist for compatibility among System/360 models.
The major elements of the Model 165 computing system are illustrated in Figure 10.05.1. Each component and its new features are discussed
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Architecture Implementation Alterations
Two alterations have been made to the system action taken on a Model 165 during the execution of certain instructions common to both
System/370 and System/360 models. The first involves all instructions that check the validity of operands involved in packed decimal
operations. On the Model 165. an invalid sign in an operand causes the instruction to be suppressed (never executed) rather than terminated during execution as is done on System/360 models. Suppression, rather than termination. of an instruction when an invalid sign occurs insures that the data fields involved remain unchanged. Therefore, when a program check occurs. a routine can be executed that inspects the field that has the invalid sign.
For example. when an invalid sign results from packing an entirely blank field. the sign can be corrected by programming. and transaction deletion or program termination is avoided.
The second alteration concerns the recognition of a storage protection exception during the execution of an EDIT or an EDIT AND MARK instruction. On a Model 165 a protection exception always occurs when a pattern character is fetched from a location protected for
storing but remains unchanged during the edit operation. This change eliminates unpredictable system operation during editing on a Model 165. The occurrence of a protection exception for the situation described is model-dependent for System/360 models.
Interval Timer (Standard)
The interval timer in decimal location 80 in fixed processor storage of a Model 165 has a resolution of 3.33 ms instead of the 16.6 ms
resolution (with 60-cycle power) implemented for the standard timer on the Model 65. Its maximum time period remains 15.5 hours. The higher resolution of this interval timer will eliminate many of the problems encountered in accounting routine accuracy caused by task execution durations that are less than the 16.6 ms resolution.
Time of Day Clock (Standard)
This new clock is a binary counter of 52 bits with a cycle of approximately 135 years. I t is updated every microsecond. Two new instructions (SET CLOCK and STORE CLOCK) are provided to set the time and to request that the current time be stored in a specified double-word of processor storage. The time can be set only when the CPU is in supervisor state and only when the clock security switch on the system console panel is in the enable set position.
The time of day clock can be used for more accurate time stamping than the interval tjmer, Accurate time of day can be maintained because the clock stops only when CPU power is turned off. The interval timer cannot be as accurate as the clock for time of day maintenance because i t is not updated when the system is in the stopped state. and its updating may be omitted under certain conditions of excessive system activity. The 15.5-hour cycle time of the interval timer is also a restriction. The time of day clock better answers the timing needs of teleprocessing and real-time applications.
CPU Cooling
The heat generated by the logic boards in the Model 165 CPU and its associated power frames is removed by forced air and a closed-loop water circulation system. Use of a liquid coolant in addition to air is required because of the amount of heat generated by the densely packed circuits in the CPU.
The user must supply 30 gallons of cooled water per minute (450 to 600 F.> to the coolant distribution unit (CDU>, which is housed in a stand-alone frame that also contains power and the power
distribution unit. Water is supplied to the CDU in pipes under the raised floor. The chilled water entering the CDU is used to control the temperature of the internal water that passes through the
cpu.
That is, the user-supplied water does not enter the closed-loop system of the
cpu.
(See Figure 10.10.1.> The COU houses the necessarycontrols to maintain the proper temperature in the closed-loop system.
The user must supply the controls to maintain the temperature of the chilled water supplied to the CDU.
User-supplied water (45°- 60°F)
...
Figure 1 .LV • .LV • n 1 n 1 .L.
Coolant Di1bution Unit
I' Closed-loop . . - - - -. . . water cooling
system in CPU
conceptual Model 165
flow of the water
CPU
' .
cooling system in the
The use of water as the cooling liquid offers several advantages.
First, i t is readily available. The chilled water normally supplied for air conditioning is acceptable. Second, water offers safety
features. Low pressure is required and the cooling system can operate at room temperature, thereby eliminating problems with condensation.
Last, a simplified circulation system suffices, with relatively few moving parts and less exposure to leaks. Pipe components within the
cpu
are separated easily, and the valved connections close off automatically to prevent water from escaping.12