Sun Microsystems, Inc.

Lsi Logic Corporation

Chakra R Srivatsa

Satish Padmanabhan

David J Greenhill

Robert K Yu

James A Bauman

Ronald J Melanson

Shailesh I Shah

A multiplication accumulation circuit (abbreviated as &ldquo;MAC&rdquo;) has five input buses that carry signals for operands A, B, C, D and E, a control bus that carries signals for controlling the operations performed on the received operands, and an output bus that carries a signal generated by the MAC. Each of operands A, B, C and D can be four different operands that are used as follows by the MAC: (1) to perform two multiplications simultaneously, and (2) to perform an addition of the products of the two multiplications and the fifth operand E, e.g. generate on the output bus a signal of value A*C&plus;B*D&plus;E. Alternatively, operands A and B can be, respectively, the upper and lower halves of a first double word to be used as a multiplicand. Similarly, operands C and D can be the upper and lower halves of a second double word to be used as a multiplier. In this case, the four operands A, B, C and D are used as follows by the MAC: (1) to perform a single multiplication of the first double word with the second double word, and (2) to perform an addition of the product of the double word multiplication, and the fifth operand E, e.g. generate on the output bus a signal of value &lsqb;A,B&rsqb;*&lsqb;C,D&rsqb;&plus;E.

Circuit and method for multiplying and accumulating the sum of two products in a single cycle

An IC includes a plurality of functional blocks each having a discrete block-level architecture. The functional blocks are connected to one another via metal interconnect lines defined by an interconnect architecture. One or more of the functional blocks includes a spare (i.e., unused) repeater amplifier. Where a repeater amplifier inserted in a particular long line of the interconnect structure would decrease the signal propagation delay through the long line, the interconnect architecture is modified so that the long line is routed through the spare repeater amplifier. Such modification decreases the signal propagation delay of the long line without requiring a modification of the block-level architecture.

Spare repeater amplifiers for long lines on complex integrated circuits

Circuits and methods for eliminating hold time violations are disclosed. A DE-type flip-flop latches a data input signal on a data input terminal a fraction of a clock period before a triggering edge of the clock signal. The DE-type flip-flop provides a data output signal for a full clock period beginning after the triggering edge of the clock signal. The DE-type flip-flop includes a latch having its data output terminal coupled to the data input terminal of a flip-flop. The flip-flop clock input pin and the latch enable terminal of the latch are connected to a clock line. The DE-type flip-flop used in place of a standard flip-flop, in which a hold time violation occurs, eliminates the hold time violation.

Method and circuit for eliminating hold time violations in synchronous

A method includes operating a general purpose computer system to minimize signal-propagation delay time of a long line of a simulated circuit. A design engineer empirically derives two rule bases, the first of which determines whether to divide the long line into two or more segments by inserting repeater amplifiers into a long line to minimize the propagation delay through the line. The second rule base relates optimum amplifier size for driving long lines to line length. These rule bases are stored in a main memory of the computer system. The computer system is configured to apply the first rule base to the long line to determine whether to divide the long line into two or more segments by inserting repeater amplifiers, and to apply the second rule base to optimize the size of each of the repeater amplifiers. The resulting long line, segmented by size-optimized repeater amplifiers, provides minimal signal-propagation delay.

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Chakra R Srivatsa