Via Technologies, Inc.

Via Alliance Semiconductor Co., Ltd.

Ip-first, LLC

Centaur Technology, Inc.

Brent Bean

G Glenn Henry

Terry J Parks

Thomas A Crispin

Thomas C McDonald

Rodney E Hooker

Darius D Gaskins

Colin Eddy

Stephan Gaskins

Gerard M Col

Bryan Wayne Pogor

John D Bunda

In one embodiment, a microprocessor, comprising: first logic configured to dynamically adjust a maximum prefetch count based on a total count of predicted taken branches over a predetermined quantity of cache lines; and second logic configured to prefetch instructions based on the adjusted maximum prefetch count.

Branch density detection for prefetcher

A microprocessor includes a plurality of cores, a shared cache memory, and a control unit that individually puts each core to sleep by stopping its clock signal. Each core executes a sleep instruction and responsively makes a respective request of the control unit to put the core to sleep, which the control unit responsively does, and detects when all the cores have made the respective request and responsively wakes up only the last requesting cores. The last core writes back and invalidates the shared cache memory and indicates it has been invalidated and makes a request to the control unit to put the last core back to sleep. The control unit puts the last core back to sleep and continuously keeps the other cores asleep while the last core writes back and invalidates the shared cache memory, indicates the shared cache memory was invalidated, and is put back to sleep.

Method and apparatus for waking a single core of a multi-core microprocessor, while maintaining most cores in a sleep state

A method of retiring cache lines from a response buffer array to an icache array of a processor including providing sequential addresses to the icache array and to a response buffer array during successive clock cycles, detecting a first address hitting the response buffer array during a first clock cycle, during a second clock cycle that follows the first clock cycle, performing a first zero clock retire to write a first cache line from the response buffer array to the icache array, and during the second clock cycle, bypassing a second address which is one of the sequential addresses. The second address is bypassed given the assumption that it will likely hit the response buffer array in a subsequent cycle. If the second address missed the response buffer array, the bypassed address is replayed with a slight time penalty, which is outweighed by the time savings of zero clock retires.

Processor with instruction cache that performs zero clock retires

A method of operating a processor including performing successive read cycles from an instruction cache array and a line buffer array including providing sequential memory addresses, detecting a read hit in the line buffer array, and performing a zero clock retire while performing successive read cycles. The zero clock retire includes switching the instruction cache array from a read cycle to a write cycle for one cycle, selecting a line buffer and providing a cache line stored in the selected line buffer to be stored into the instruction cache array at an address stored in the selected line buffer, and bypassing a sequential memory address being provided to the instruction cache array during the zero clock retire. If the bypassed address missed the line buffer array, the bypassed address may be replayed with a slight time penalty, which is outweighed by the time savings of zero clock retires.

A secure memory, key expansion logic, and decryption logic are provided for a microprocessor that executes encrypted instructions. The secure memory stores a plurality of decryption key primitives. The key expansion logic selects two or more decryption key primitives from the secure memory and then derives a decryption key from them. The decryption logic uses the decryption key to decrypt an encrypted instruction fetched from the instruction cache. The decryption key primitives are selected on the basis of an encrypted instruction address, one of them is rotated by an amount also determined by the encrypted instruction address, and then they are additively or subtractively accumulated, also on the basis of the encrypted instruction address.

Key expansion logic using decryption key primitives

A microprocessor is provided in which an encrypted program can replace the decryption keys that are used to decrypt sections of the encrypted program. The microprocessor may be decrypting and executing a first section of the encrypted program when it encounters, decrypts, and executes an encrypted store-key instruction to store a new set of decryption keys. After executing the store-key instruction, the microprocessor decrypts and executes a subsequent section of the encrypted program using the new set of decryption keys. On-the-fly key switching may occur numerous times with successive encrypted store-key instructions and successive sets of encrypted instructions.

Microprocessor with on-the-fly switching of decryption keys

A microprocessor and method are provided for securely decrypting and executing encrypted instructions within a microprocessor. A plurality of master keys are stored in a secure memory. Encrypted instructions are fetched from an instruction cache. A set of one or more master keys are selected from the secure memory based upon an encrypted instruction fetch address. The selected set of master keys or a decryption key derived therefrom is used to decrypt the encrypted instructions fetched from the instruction cache. The decrypted instructions are then securely executed within the microprocessor. In one implementation, the master keys are intervolved with each other to produce a new decryption key with every fetch quantum. Moreover, a new set of master keys is selected with every new block of instructions.

Decryption of encrypted instructions using keys selected on basis of instruction fetch address

A microprocessor includes compressed and uncompressed microcode memory storages, having N-bit wide and M-bit wide addressable words, respectively, where N&#x3c;M. The microprocessor also includes a fetch unit, an instruction translator, and an execution stage. When the instruction translator receives an architectural instruction, it writes information identifying source and destination registers specified by the architectural instruction to an indirection register. It also issues one or more fetch addresses to retrieve a sequence of one or more microcode instructions from one of the uncompressed microcode memory storage and the compressed microcode memory storage to implement the architectural instruction. It merges information in the indirection register with the sequence of one or more microcode instructions to generate a sequence of one or more implementing microinstructions.

Microprocessor using compressed and uncompressed microcode storage

A microprocessor conditionally grants a request to switch from a normal execution mode in which encrypted instructions cannot be executed, into a secure execution mode (SEM). Thereafter, the microprocessor executes a plurality of instructions, including a store-key instruction to write a set of one or more cryptographic key values into a secure memory of the microprocessor. After fetching an encrypted program from an instruction cache, the microprocessor decrypts the encrypted program into plaintext instructions using decryption logic within the microprocessor's instruction-processing pipeline.

Microprocessor with secure execution mode and store key instructions

System and method of determining memory ownership on cache line basis for detecting self-modifying code. An ownership queue stores cache line addresses and corresponding ownership indexes. The cache line data is translated into instructions, and each instruction is provided with an ownership index of an associated entry in the ownership queue. Each new cache line address is compared with the destination address of each store instruction, and each destination address, when determined, is compared with each cache line address in the ownership queue. Matching entries are marked as stale, and each instruction derived from a stale entry causes an exception when ready to retire. In this manner, a hit between a cache line and a corresponding store instruction causes an exception. An exception flushes the processor to resolve the potential modified code condition.

System and method of determining memory ownership on cache line basis for detecting self-modifying code

A system and method of determining memory ownership on a cache line basis for detecting self-modifying code including code with looping instructions. An ownership queue includes multiple entries for determining memory ownership on a cache line basis. An ownership index and a wrap bit are determined for each cache line in the ownership queue, which are provided with each instruction derived from the same cache line. When an instruction is issued for execution, the ownership index provided with the instruction is used to access the corresponding entry in the ownership queue. If the instruction and entry wrap bits do not match, then an overwrite of the cache line is detected. The instruction is marked to invoke a first exception, which is performed when the instruction is ready to retire. The first exception flushes the processor, prevents the instruction from being retired, and re-fetches the instruction to continue processing.

System and method of determining memory ownership on cache line basis for detecting self-modifying code including code with looping instructions

A processor that determines memory ownership on a cache line basis for detecting self-modifying code including modification of a cache line with an executing instruction. An ownership index and corresponding cache line address are entered for each cache line into an ownership queue. The ownership index is provided with each instruction derived from the cache line. When the instruction is issued, an executing bit is set in the corresponding entry. When a destination address of a store instruction matches an entry in the ownership queue, the store instruction is marked to invoke an executing exception if the executing bit of the entry is set. When a store instruction that is ready to retire is marked to invoke the executing exception, the store instruction is allowed to retire, the processor is flushed, and the next instruction after the store instruction is re-fetched to continue processing.

System and method of determining memory ownership on cache line basis for detecting self-modifying code including modification of a cache line with an executing instruction

A system and method for determining memory ownership on a cache line basis for detecting self-modifying code with instructions that overlap cache line boundaries. An ownership index and a cache line address are entered into the ownership queue for each cache line. The cache lines are translated into instructions, and a straddle bit is set for each instruction that was derived from cache line data that overlapped two cache lines. A stale bit is set for any entry of the ownership queue that collides with a store instruction. Each instruction issued for execution is marked with a first exception when the stale bit of the corresponding ownership queue entry is set, or when the straddle bit of the issued instruction and a stale bit of a next sequential entry are both set. A first exception is performed for each instruction ready to retire that is marked with the first exception.

System and method of determining memory ownership on cache line basis for detecting self-modifying code including code with instruction that overlaps cache line boundaries

Single core wakeup multi-core synchronization mechanism

A microprocessor includes a plurality of processing cores each comprises a corresponding memory physically located inside the core and readable by the core but not readable by the other cores ('core memory'). The microprocessor also includes a memory physically located outside all of the cores and readable by all of the cores ('uncore memory'). For each core, the uncore memory and corresponding core memory collectively provide M words of storage for microcode instructions fetchable by the core as follows: the uncore memory provides J of the M words of microcode instruction storage, and the corresponding core memory provides K of the M words of microcode instruction storage. J, K and M are counting numbers, and M=J+K. The memories are non-architecturally-visible and accessed using a fetch address provided by a non-architectural program counter, and the microcode instructions are non-architectural instructions that implement architectural instructions.

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Austin, TX, United States of America

Brent Bean