Suspended instruction restart processing system based on a checkpoint microprogram address

Claim 1

An apparatus for instruction restart processing in a microprogram controlled data processing apparatus of the type in which an instruction read from a main storage is executed in accordance with a microprogram, said instruction restart processing apparatus comprising: first storage means for storing a read address of a control program storage which stores a microprogram; means for causing said first storage means to store said read address of said control program storage in accordance with a designation by said microprogram; second storage means for storing information indicating whether said read address is stored in said first storage means; judgement means for checking the content of said second storage means in accordance with said microprogram; and means for restarting execution of said instruction by reading said microprogram stored at said read address stored in said first storage means; wherein a predetermined microinstruction in said microprogram causes said read address to be stored in said first storage means; and wherein when a suspension of instruction execution of said instruction occurs while executing said instruction and said suspended instruction starts to be executed, the content of said second storage means is checked; wherein in a case where storing of said read address has been performed, execution of said suspended instruction is restarted by reading said microprogram at said read address; and wherein in a case where storing of said read address has not been performed, execution of said suspended instruction is restarted by reading again said suspended instruction from said main storage.

Claim 2

An apparatus for instruction restart processing in a microprogram controlled data processing apparatus of the type in which an instruction read from a main storage is executed in accordance with a microprogram, said instruction restart processing apparatus comprising: first storage means for storing a read address of a control program storage which stores a microprogram; means for causing said first storage means to store said read address of said control program storage in accordance with a designation by said microprogram; second storage means for storing information indicating whether said read address is stored in said first storage means; judgement means for checking the content of said second storage means in accordance with said microprogram; and means for restarting execution of said instruction by reading said microprogram stored at said read address stored in said first storage means; wherein a predetermined microinstruction in said microprogram causes said read address to be stored in said first storage means; and wherein when a suspension of instruction execution of said instruction occurs while executing said instruction and said suspended instruction starts to be executed, the content of said second storage means is checked; wherein in a case where storing of said read address has been performed, execution of said suspended instruction is restarted by reading said microprogram at said read address; and wherein in a case where storing of said read address has not been performed, execution of said suspended instruction is restarted by reading again said suspended instruction from said main storage.

Claim 3

A method for instruction restart processing in a microprogram controlled data processing apparatus of the type in which an instruction read from a main storage is executed in accordance with a microprogram, and said instruction being included within an instruction execution microprogram having a micro instruction for determining an address for reading a microprogram for restarting execution of the instruction after suspension of instruction execution, comprising the steps of: checking to determine whether a read address of a restart microprogram has been saved or not, when suspension of instruction execution occurs while executing an instruction and checking to determine whether the cause of the suspension is removed thereafter; reading said restart microprogram at a saved read address when a suspension of instruction execution occurs and starting execution of the suspended instruction, when said read address has been saved; starting execution of said suspended instruction from a read operation of said suspended instruction from said main storage when said read address had not been saved; providing a first unit for performing a preparation process for execution of an instruction by reading the instruction from a main storage; and providing a second unit for executing the instruction in accordance with a microprogram by again reading the instruction from the main storage; wherein at least said first and second units are pipelined to each other; wherein said second unit comprises first storage means for storing a read address related to an address of said microprogram at the time of executing said instruction, and second storage means for storing information indicating whether said read address has been stored; wherein when a suspension of instruction execution occurs while executing said instruction and said suspension of instruction execution cause is removed thereafter, the content of said second storage means is checked; and wherein in a case where said read address has been stored, said suspended instruction starts to be executed by reading said microprogram at said read address, and said first unit is caused to start reading the next instruction after said suspended instruction from said main storage.

Claim 4

A method for instruction restart processing in a microprogram controlled data processing apparatus of the type in which an instruction read from a main storage is executed in accordance with a microprogram, and said instruction being included within an instruction execution microprogram having a micro instruction for determining an address for reading a microprogram for restarting execution of the instruction after suspension of instruction execution, comprising the steps of: checking to determine whether a read address of a restart microprogram has been saved or not, when suspension of instruction execution occurs while executing an instruction and checking to determine whether the cause of the suspension is removed thereafter; reading said restart microprogram at a saved read address when a suspension of instruction execution occurs and starting execution of the suspended instruction, when said read address has been saved; starting execution of said suspended instruction from a read operation of said suspended instruction from said main storage when said read address had not been saved; providing a first unit for performing a preparation process for execution of an instruction by reading the instruction from a main storage; and providing a second unit for executing the instruction in accordance with a microprogram by again reading the instruction from the main storage; wherein at least said first and second units are pipelined to each other; wherein said second unit comprises first storage means for storing a read address related to an address of said microprogram at the time of executing said instruction, and second storage means for storing information indicating whether said read address has been stored; wherein when a suspension of instruction execution occurs while executing said instruction and said suspension of instruction execution cause is removed thereafter, the content of said second storage means is checked; and wherein in a case where said read address has been stored, said suspended instruction starts to be executed by reading said microprogram at said read address, and said first unit is caused to start reading the next instruction after said suspended instruction from said main storage.