IP Integration : What is the difference between stitching and weaving?

I should write a article on: What is the difference between reusing and salvaging…

by David Murray, 12/15/2010, Design and Reuse

As a hardware design engineer, I was never comfortable when someone talked about IP integration as ‘stitching a chip together’. First of all, it sounded like a painful process involving sharp needles, usually preceded by a painful accident. I happened to be the recipient of said stitches when, at 8 years of age, I contested a stairs post with my forehead, and sorely lost. I have to say, luckily, I have been quite adept at avoiding the needle and thread ever since. That was of course until once when, an hour before that important customer presentation, my top-shirt button, due to an over enthusiastic yawn, pinged across my hotel room floor like a nano-UFO. A panicked retrieval of the renegade button was followed quickly with a successful hunt for an elusive emergency sewing-kit. The crisis quickly dissipated as I stitched back the button in a random-but-directed type of methodology. Needle-less to say stitching, whilst sometimes necessary, makes me uncomfortable.

Stitching, according to Wikipedia, is “.. the fastening of cloth, leather, furs, bark, or other flexible materials, using needle and thread. Its use is nearly universal among human populations and dates back to Paleolithic times (30,000 BCE).” It also states that stitching predates the weaving of cloth. So, 32,000 years later, in these hi-tech times we are still stitching things together. It’s not fur this time, but ‘ports’. Stitching a chip together involves connecting ports together with wires. (Note the terminology also where, if you don’t use certain ports you ’tie’ them off).

Weaving is a different game altogether. One definition simplifies weaving as ‘creating fabric’. Thus a key differentiator between stitching and weaving is that stitching may refer to fixing/mending things whilst weaving is used to create. Stitching is an emergency, an ah-hoc approach (please refer to my stitched button above) whilst weaving is more structured, more planned. Stitching invokes the image of being bent over, eyes squinted, immersed in the tiniest of detail. Weaving is more graceful and productive. In IC design flow terms, I equate stitching with scripting. It is task that is useful to join pieces of the flow together. Weaving creates something. It transforms thread to cloth, and therefore equates more to synthesis. Weaving is a process.

So when it came to developing and naming a tool used to effectively integrate IP and create a chip hierarchy, in a structured manner, we didn’t consider consider ‘STITCHER’ – It had to be ‘WEAVER’.

Stitching is important to fix things, and is necessary in emergency situations, however it has its limitations and as if used as a core creation process, it may come undone. So as I ranted on during that vital presentation, as I got to the cusp of the value-add, I curbed my enthusiasm, keep it slightly in check just in case those button stitches came undone and resulted in a serious eye injury of an altogether innocent customer. What then, of those poor stitched chips? What if those threads start to unravel and your chip integration is running very late. You may have to resort to different type of Weaving, when dealing with your management, customers or partners.

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