发明授权
US5787030A Correct and efficient sticky bit calculation for exact floating point
divide/square root results
失效
精确浮点除法/平方根结果的正确和有效的粘性位计算
- 专利标题: Correct and efficient sticky bit calculation for exact floating point divide/square root results
- 专利标题(中): 精确浮点除法/平方根结果的正确和有效的粘性位计算
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申请号: US498397申请日: 1995-07-05
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公开(公告)号: US5787030A公开(公告)日: 1998-07-28
- 发明人: J. Arjun Prabhu , Grzegorz B. Zyner
- 申请人: J. Arjun Prabhu , Grzegorz B. Zyner
- 申请人地址: CA Mountain View
- 专利权人: Sun Microsystems, Inc.
- 当前专利权人: Sun Microsystems, Inc.
- 当前专利权人地址: CA Mountain View
- 主分类号: G06F7/537
- IPC分类号: G06F7/537 ; G06F7/00 ; G06F7/483 ; G06F7/506 ; G06F7/52 ; G06F7/535 ; G06F7/552 ; G06F7/76 ; G06F7/38
摘要:
Quotient digit selection logic is modified so as to prevent a partial remainder equal to the negative divisor from occurring. An enhanced quotient digit selection function prevents the working partial remainder from becoming negative if the result is exact. The enhanced quotient digit selection logic chooses a quotient digit of zero instead of a quotient digit of one when the actual partial remainder is zero. Using a five bit estimated partial remainder where the upper four bits are zero, a possible carry propagation into fourth most significant bit is detected. This can be accomplished by looking at the fifth most significant sum and carry bits of the redundant partial remainder. If they are both zero, then a carry propagation out of that bit position into the least significant position of the estimated partial remainder is not possible, and a quotient digit of zero is chosen. In the alternative case in which one or both of the fifth most significant carry or sum bits of the redundant partial remainder are ones, a quotient digit of one is chosen. This provides a one cycle savings since negative partial remainders no longer need to be restored before calculating the sticky bit. Extra hardware is eliminated because it is no longer necessary to provide any extra mechanism for restoring the preliminary final partial remainder. Latency is improved because no additional cycle time is required to restore negative preliminary partial remainders. An optimized five-level circuit is shown which implements the enhanced quotient selection function.
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