摘要
对于高性能CPU设计,特别是在16 nm以及更高级的工艺节点上,signoff的corner很多,增加公共时钟路径长度、改善各RC端角下时钟延迟的一致性、降低设计的局部时钟偏斜已经成为数字后端设计师的共识。Cadence innovus工具新增的multi-tap FlexHtree结构时钟树方案不仅提供了H-tree对称的时钟缓冲器单元结构和相等的线长特点,而且其对几何对称性降低了要求,确保了时序单元摆放完毕后就可以进行时钟树综合。建立了一个自动化的FlexHtree实现流程来降低不同corner下的时钟偏斜。详细讨论了FlexHtree tap点的数量以及子树时钟综合引擎对时钟偏斜和设计时序的影响,进而找到了一个较好的FlexHtree实现方案。最后从时序、功耗和单元数量等方面对FlexHtree、CCOPT和鱼骨型Fishbone结构时钟树进行了较为全面的比较,从而得出该设计更适合采用灵活的FlexHtree结构。
For high performance CPU design, especially on 16 nm and advanced process nodes, with the increase in the number of signoff corner, increasing the clock common path, improving the clock latency correlation on various RC corners, decreasing local skew of design, those are our common view. The Cadence innovus Flexible H-tree（FlexHtree） feature not only provides the symmetric buffer structure and equal wire lengths benefits of an H-tree, but also relaxes the requirement to be geometrically symmetric, enabling clock tree synthesis even in floorplans with sink placement. This paper presents an automatic Flexible H-tree flow to decrease clock skew on different corners. Meanwhile, this paper will discuss the impact of multi-taps counts and synthesis engines of the sub-tree on clock skew and design timing in details, then choses a better solution. Finally, in terms of timing, power consumption,and instance counts results, the design mentioned in this paper is suitable to use Flexible H-tree clock structure in comparison to CCOPT and fishbone structure clock tree.
作者
彭书涛
黄薇
边少鲜
杜广山
Peng Shutao;Huang Wei;Bian Shaoxian;Du Guangshan(Tianjing Phytium Technology Co.,Ltd.,Tianjing 102209,China;Cadence Design Systems,Inc.,Shanghai 201204,China)
出处
《电子技术应用》
2018年第8期5-9,12,共6页
Application of Electronic Technique
