Floating point multiply accumulator

An integrated circuit comprising:

• a multiplier to produce a product from two floating point multiplicands having a first exponent weight;
• a floating point conversion unit to convert the product from the first exponent weight to a converted product with a second exponent weight;
• an adder to produce a present sum from the converted product and a previous sum having the second exponent weight;
• a post-normalization unit to convert the present sum to a floating point resultant having the first exponent weight;
• wherein:
• the product comprises an exponent having a least significant bit weight of one and a mantissa in carry-save format;
• and
• the adder is configured to receive a converted product having an exponent with a least significant bit weight of thirty-two and a mantissa in carry-save format.

An integrated circuit comprising:

• a multiplier to produce a product from two floating point multiplicands having a first exponent weight;
• a floating point conversion unit to convert the product from the first exponent weight to a converted product with a second exponent weight;
• an adder to produce a present sum from the converted product and a previous sum having the second exponent weight;
• a post-normalization unit to convert the present sum to a floating point resultant having the first exponent weight;
• wherein the converted product comprises a three bit exponent field having a least significant bit weight of thirty-two.

A floating point multiply-accumulate circuit comprising:

• an exponent path including:
• an exponent summer to sum two input exponents having a first weight to produce a product exponent;
• an exponent conversion unit coupled to the output of the exponent summer, to convert the product exponent to a second weight;
• and
• an exponent accumulation stage to choose a larger exponent from the product exponent and an accumulated exponent;
• and
• a mantissa path including:
• a mantissa multiplier to multiply two input mantissas and produce a product mantissa;
• a mantissa shifter to shift the product mantissa responsive to the exponent conversion unit in the exponent path;
• and
• a mantissa accumulator to accumulate shifted product mantissas;
• wherein the mantissa shifter is configured to shift the product mantissa by a number of bit positions equal to a value of the least significant N bits of the product exponent, where N is a predetermined integer.

A floating point multiply-accumulate circuit comprising:

• an exponent path including:
• an exponent summer to sum two input exponents having a first weight to produce a product exponent;
• an exponent conversion unit coupled to the output of the exponent summer, to convert the product exponent to a second weight;
• and
• an exponent accumulation stage to choose a larger exponent from the product exponent and an accumulated exponent;
• and
• a mantissa path including:
• a mantissa multiplier to multiply two input mantissas and produce a product mantissa;
• a mantissa shifter to shift the product mantissa responsive to the exponent conversion unit in the exponent path;
• and
• a mantissa accumulator to accumulate shifted product mantissas;
• wherein the mantissa shifter is configured to shift the product mantissa by a number of bit positions equal to a value of the least significant five bits of the product exponent.

A floating point multiply-accumulate circuit comprising:

• an exponent path including:
• an exponent summer to sum two input exponents having a first weight to produce a product exponent;
• an exponent conversion unit coupled to the output of the exponent summer, to convert the product exponent to a second weight;
• and
• an exponent accumulation stage to choose a larger exponent from the product exponent and an accumulated exponent;
• and
• a mantissa path including:
• a mantissa multiplier to multiply two input mantissas and produce a product mantissa;
• a mantissa shifter to shift the product mantissa responsive to the exponent conversion unit in the exponent path;
• and
• a mantissa accumulator to accumulate shifted product mantissas;
• wherein the exponent conversion unit is configured to convert the product exponent to have a least significant bit weight equal to thirty-two.

A method of performing a multiply-accumulate operation comprising:

• multiplying two floating point mantissas and summing two floating point exponents to form a product;
• converting the product to have a different least significant bit weight exponent field;
• accumulating the converted product;
• and
• post-normalizing the accumulated product;
• wherein converting comprises:
• shifting a mantissa of the product by an amount equal to the value of the least significant N bits of the exponent of the product, where N is a predetermined integer;
• and
• zeroing the least significant N bits of an exponent of the product.

A method of performing a multiply-accumulate operation comprising:

• multiplying two floating point mantissas and summing two floating point exponents to form a product;
• converting the product to have a different least significant bit weight exponent field;
• accumulating the converted product;
• and
• post-normalizing the accumulated product;
• wherein converting comprises:
• shifting a mantissa of the product by an amount equal to the value of the least significant five bits of the exponent of the product;
• and
• zeroing the least significant five bits of an exponent of the product.

A method of performing a multiply-accumulate operation comprising:

• multiplying two floating point mantissas and summing two floating point exponents to form a product;
• converting the product to have a different least significant bit weight exponent field;
• accumulating the converted product;
• and
• post-normalizing the accumulated product;
• wherein accumulating comprises:
• comparing an exponent of a first converted product to an exponent of a second converted product;
• conditionally shifting right by a fixed amount the mantissa of the converted product having a smaller exponent;
• selecting the larger exponent as a resultant exponent;
• and
• producing a resultant mantissa from a mantissa of the first converted product and a mantissa of the second converted product.