[SI-LIST] FW: Off Topic Question

From: "Bill Reams" <breams@xxxxxxxxxxxxxx>
To: "'Si-List' (E-mail)" <si-list@xxxxxxxxxxxxx>
Date: Fri, 8 Nov 2002 08:32:08 -0600
{snip}
For your "typical" projects, how many circuit board revisions does it =
=3D
take to go from the block diagram stage to full production release?

{snip}

Some have asked about the results of this survey so here is the tally of =
responses:

It appears that the number of board spins has a bimodal distribution. =
The first peak is at two spins. This group tends to have the logic =
correct the first time around for most of their projects. The second =
spin then becomes clean-up for minor details that were missed. Within =
this group are what appear to be two subgroups that I would have a hard =
time distinguishing between due to the unscientific nature of the poll.

Subgroup A (3 responses) will typically ship the first spin. From =
reading the comments, this group appears to perform more prelayout =
simulation and review prior to layout. Some also mentioned post layout =
review prior to board fab. This group sometimes has the second spin =
although they tend to think of the second spin as feature creep created.

Subgroup B (4 responses) tend to do a good job on the first board then =
do a second spin for minor clean-ups. Sometimes this group requires a =
third spin. Typical reasons for third spins were not having 100% correct =
schematics at the first spin (EBKAC errors) and feature creep. For those =
that asked, this is the group where I've tended to fall when there is no =
feature creep.

The second main peak within our bimodal distribution are the 3 responses =
that typically have 3-5 board spins. Not enough reasoning was given for =
me to know why 3-5 is the number (e.g., feature creep, complex designs =
with new unproven chips, etc).

Again, thank you all for the responses. The information is certainly =
useful in providing us with "industry standard" evidence for creating =
new project schedules with more than a single board spin.
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[SI-LIST] FW: Off Topic Question

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