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AR# 11007

3.2i CORE Generator - 18x18 (signed) multiplier for Virtex-II uses too many multiplier blocks.

Description

Keywords: CORE Generator, COREGen, Virtex-II, multiplier

Urgency: Standard

General Description:
When I use the 18x18 signed multiplier for the Virtex-II multiplier core in D_IP2 (Mult_gen_v2_0), the multiplier uses 4 multiplier blocks instead of 1.

Solution

This occurs because of the way in which the multiplier was coded. When coding work began on mult_gen_v2_0, the Virtex-II "fabric" was still somewhat unclear; subsequently, when the coding for the 18x18 block-multiplier was done, a subtle mistake was made. Although the block multiplier can cope with 18-bit signed numbers, the IP developers didn't realize this at the time, and thought that the addition of the sign bit would necessitate the use of several block-multipliers to perform this task.

This issue has been fixed in D_IP3, which was released on March 9, 2001.
AR# 11007
Date Created 02/15/2001
Last Updated 08/23/2002
Status Archive
Type General Article