> I remember when Protel bought "NeuroRoute" from Gene Marsh (?) At the time, > which was not that long ago, EVERYONE was saying it, NeuroRoute, was the > best thing since sliced bread. > > What happened?
Well, we found that bread is very fattening (lots of carbs)! And unless you eat the whole grain hippy stuff, it doesn't have much fiber. And bread has gotten expensive. And it turns moldy quickly...
But seriously, folks, I like the 99SE autorouter OK. It's fast. I have to tweak the design rules a lot to get the results I like. But the fact that it's fast lets you do a lot of tweak-and-try runs. Don't expect to get good results on the first attempt. It will screw you on split planes, too. Either don't use split planes, or check the autorouter's work very carefully afterwards to make sure it didn't put a power via into the wrong plane or short planes with a power via. It will misbehave - I've seen it do that. Work with layer bias, and try diagonal bias on some layers - it may work better than horiz and vert bias in some cases. On 6 layer boards, I sometimes use 1 horiz, 1 vert, 1 45 degree right slant, and 1 45 degree left slant layers. As far as unrouting (or rerouting) locked tracks, the trick is that your preroute must be 100% routed AND locked. If it's only partially routed, 99SE will unroute it. If you go right up to 1 mil away from the pad and then stop your track, that counts as a partial route to the autorouter, and it will get ripped up.
It will also rip up any track that contains arcs (at least that was my experience when dumping a PCI card with meandered clock line at the router - after hand routing all the PCI signals).
It will also rip up fills that are part of footprints - such as on SOT-89 devices. The Altium supplied library SOT-89 can be used to demonstrate this - though I would not suggest using this in a design as I think fill was missing the all important mask and paste fills. It is a neat way of making more routing channel space - just remove some component copper.
I have never been impressed by the P99SE router, but I hear others say they used it. I also used the NeuroRoute release - and got a credit due to poor performance. I think this product had possibilities but the code was *so* complex it was unmaintainable and there was many examples of designs it couldn't do a reasonable job on. I found a couple. Funnily enough, if I recall correctly, poor copper sharing was one of the problems in NeuroRoute, something that I see is still an issue in P99SE and now Situs.
The P99SE does not clean up well. The DXP/P2004 Situs router has some clean-up passes that work pretty well I think. It is a shame that the routing passes seem difficult to get working and it is so slow (at least when it is getting close to completion)- at least that is my experience, which is not a great deal as I tend to drop autorouters fairly quickly when they don't work for me. Maybe I expect too much or my designs are not good autorouter candidates or I am not good at placement for autorouting.
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