( ESNUG 278 Item 6 ) ----------------------------------------------- [1/28/98]
Subject: (ESNUG 276 #8) Views On Off-The-Shelf Standard ASIC Libraries
> I'm fishing for information, horror stories, and user insights concerning
> off-the-shelf standard cell ASIC libraries. (In particular, but not
> limited to, how they work with Synopsys synthesis.)
From: monks@quebabi.sps.mot.com <Morgan Monks>
John,
I would strongly recommend that when you evaluate these "off-the-shelf"
ASIC libraries that you look at timing convergence to a final routed design.
In my ASIC experience many vendor's libraries don't have the insight that
make the place and route make a small timing correct chip.
Each library that I have worked with has had design input based upon the
place and route tool. We use Cell3.
- Morgan Monks
Motorola Semi-custom Chandler, Arizona
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From: "David Brantley" <dmb@dalsemi.com>
John,
We have been evaluating cell libraries and memory compilers from various
vendors since last September. By most accounts, Aspec is considered to have
the largest share of this market. We are looking for Chartered libraries
only, not multiple foundry based libraries. Also, we are concentrating on
0.5um (for 5V parts) and on .35um (for our 3V parts).
The foundry and the process you are targetting are very large factors in
trying to decide what vendor can support you. It has also been our
experience that the salesperson will "sell" you anything, doesn't matter
whether the vendor actually has the product or not. Some vendors structure
their business model such that they expect to be able to re-act quickly
enough to a customer's request that you should not have to concern yourself
whether or not they actually have the product you wish to buy or not. They
believe they can make it in time for delivery to you.
I would highly recommend that you demand to put your hands on at least a
small sample of what you are purchasing, including all views, before you
place an order. Further, I would encourage you to run DRC's, off-grid
checks, and route one or more blocks after using synthesis using the
library. This comes from our recent experiences.
Another key point is to get a clear definition from your foundry of all
documents which describe the process you are targetting and their current
revision code. Then make sure your cell library vendor complies with this
rev of these documents.
As for details of particular vendors, we have dealt with Aspec and found
their libraries to be wanting from an engineering perspective. They have
a P/N ratio of 1 in their libraries, off-grid points, the cells are not
compliant with the latest rev of the foundry's DRC documents, an inverter
is made up of 4 Xtrans (2 of which are obviously not connected but causes
the cell to be much larger than needed therfore impacting density), some
cells require routing outside of the cell boundary to make internal
connections, metal2 and metal3 are used in the cell, etc.
We are a 3+ year customer of Cascade for our internal Fab. We have had
battles with them over the past year with these libraries as they have
"changed their business model". They have put in place new management
which have taken a company which worked well with its customers and "broken"
it. We are finding DRC problems, off-grid problems, verilog model versus
actual silicon functionality problems, etc. Also, Cascade does not have
any of the processes we have requested for Chartered "off the shelf".
They believe they can "quickly turn" whatever the customer requests.
We have talked to Artisan only about memory compilers. They too have
apparently changed their business model. According to John Roar at Artisan,
they now only sell memory compilers to Foundries with a "right to
distribute" license. Artisan does not sell memory compilers directly to
end-users.
Compass (now Avant!) are trying to decide if/how they will be in the cell
library business. Avant! has a new division for design services called
Galaxy. They really want to sell you design services not just libraries
or compilers. Furthermore, they are not sure it is in their best interest
to sell you any product if you are going to use a Cadence router. If you
want to buy an Avant! router, then they will consider selling you libraries
or compilers.
We are currently evaluating cell libraries from Leda Systems. So far, we
have been very impressed with their technical ability and their products do
not appear to have the flaws we have found in the other vendors. Again, we
are early in our evaluation process, but so far we are pleased. Leda does
not have any memory compilers to offer, so we are still searching for that
solution.
As you can see from our horror stories, it is not just "plug-and-play". I
suggest you spend some time developing an evaluation strategy and then
expect to spend some "quality" time with your proposed vendors.
- David Brantley
Dallas Semiconductor Dallas, TX
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