( DAC 03 Item 35 ) ----------------------------------------------- [ 01/20/04 ]
Subject: Tanner L-Edit & T-Spice, Silvaco SmartSpice
SMALL IS BEAUTIFUL: Intially created back in the Microsoft DOS days, Tanner
has a small, but fanatical fan base of long time users who are small
themselves. Water reaches its own level. Intel isn't going to buy Tanner
tools to run on PCs, when they can afford to get special treatment from
Cadence/Synopsys/Mentor. Conversely, Cadence/Synopsys/Mentor don't want to
waste their time trying to sell to a customer whose entire annual EDA
budget is under $30 K per year. But the small players like Tanner will
eagerly go after small customers. Because to Tanner, they're big.
The only thing I can compare Tanner L-Edit Pro to is Mentor Graphics,
and that's from experience I had about 5 years ago, so take it with a
grain of salt. Also, I only use portions of L-Edit, since I work on
MicroElectroMechanical System (MEMS) and not IC design. I'm just now
starting to learn about their design rule checking, so I can't comment
much on that either. There is a parameterized cell capability which
I've never used either, since our designs have enough variety that it's
not too useful for us.
Some strengths:
- Works on a PC (don't know which of the other are PC-based), which
makes it easy to use when traveling.
- Inexpensive relative to other tools, about 3k/license, and it
never expires, although it costs about 1k per year to keep getting
upgrades.
- Very intuitive user interface.
- Once you learn the tricks, you can design at a very fast rate.
- Responsive customer support, especially when you're pointing out
an issue that they need to fix.
- New version (v11, in beta form now) adds some AutoCAD-like
features like selecting midpoints of lines.
Some weaknesses:
- Layer derivation on a chip or wafer scale can be prohibitively
slow, so I normally have the mask house do it.
- Cross-section tool won't comprehend all-angle polygons, which are
common in MEMS design.
- Cross-section tool doesn't allow conformal deposition of layers,
and doesn't understand etch selectivity between materials.
- I've had some problems in the past with it outputting bad GDS
(incorrect rotations), but they seemed to have fixed that.
- As of v10, there were some problems handling tori, but they tell
me that new versions fix that.
Overall, I think it's a good, solid tool. When you take into account
that some of the competitors are 10X the cost, and have to be renewed
yearly, you certainly can't beat it for the price. Any issues I have I
let them know about, and within the next few releases I normally see
them taken care of.
- Peter Gulvin of Xerox Corp.
I didn't go to DAC, but I recently took a serious look at Paragon IC
vs. the Tanner Tools Pro. I have about five years of experience with
Cadence Analog Artist/Virtuoso and used Tanner for a few years before
that. Paragon had great pre-sales support; they even came by our office
to install Linux and their tools on our machine. The second time was
just because we wanted to use Silvaco SmartSpice with Paragon, but the
eECAD software doesn't work with Red Hat 8, so they reinstalled with 7.2.
The Paragon tools have a very nice interface that is similar to
Virtuoso and Mentor's IC Station, except even more user friendly.
However, once we got past the eye candy, we saw that there were several
features missing that would make working with the tools more painful.
For example, when you drop down a FET symbol in the schematic, it puts
down a blank template, so every time you have to re-enter all the
information.
The Tanner schematic editor (S-Edit) and waveform viewers are very poor,
but T-Spice and L-Edit are solid. L-Edit seems to be where most of the
work in improvements has been going the last several years. Overall,
the Tanner Tools are easy to install and get running and are well
integrated.
- Brett Warneke of Dust, Inc.
I like the fact that T-Spice has lots of sim parameters to tweak so
getting virtually any circuit to converge is fairly easy.
I like most features of the T-Spice GUI; however I wish that it behaved
like most regular text editors -- T-Spice doesn't recognize my
Ctrl-arrow key strokes for some reason, and I've given up using the
Undo command or copying and pasting large sections of text from other
documents after several instances where it's messed this up; it doesn't
seem to use the Windows clipboard properly.
It simulates fairly quickly with most modest sized circuits, but for
very large circuits (which I often work with) even table mode does not
speed things up enough (for instance, I've run simulations that go for
over a day on a fast computer). This is because it is still simulating
every MOSFET as an analog device. So a weakness is that T-Spice
doesn't support true digital or mixed-mode simulation "out of the box".
I'm currently working on a pseudo-digital MOSFET model with ViewDraw
symbols using the switch (SW) model type to see if I can get a 10X run
time improvement or better. I do this so I can netlist and simulate
the digital gate portions of my circuits as switches while keeping the
analog parts as FETs, caps, resistors, etc. So far I'm having success.
But if Tanner could make this easier, that would be great. (Perhaps
there already is a way, but I haven't read about it). I'm not the
programmer type so I can't create my own C code models as the User
Guide describes.
- JP Curzan of Nova Biomimetics
Cadence has cemented their spot as the central framework for all
well-heeled analog designers, who then flesh out their system with tools
from other vendors. Small players still use PC based tools like Tanner.
- John Weiland of Intrinsix
I use Tanner L-Edit because it is cheap, and it works. I have no
experience with any of the other tools you mentioned, so I can't
comment on them. L-Edit is real popular for doing analog and mixed
signal stuff. The biggest job I have done with L-Edit was about 1/4
million transistors, and first silicon worked. For big digital jobs I
suspect it will run out of steam, but I am not experienced with that
kind of stuff. The place and route tool is okay for small to medium
digital standard cell arrays. As for analog stuff, it can draw
whatever lines and polygons the designer can dream up, and most analog
stuff is handcrafted anyways. The LVS tool is a bit mystical, can be a
pain to decipher, but it works. By the way, L-Edit started out as a
DOS app, when keeping files sizes below 1.44 Mbyte was essential for
floppies, and the application data had to fit into 640K RAM. The Ledit
guys didn't forget their humble past when they migrated to Windows.
The file sizes are still miniscule, the app is very snappy, and can run
on almost any mediocre PC. It NEVER crashes.
- David Skurnik
Tanner is a good solution for me, so that I can get kids up to speed on
design, analysis and SPICE, floor planning, etc, -- all in a 1/4 based
schedule where our terms are 7 weeks long (honest!).
Wishes...
a. Better (cheaper) documentation
b. Better tutorials (most are based on the old DOS based L-Edit which
are out of date)
c. Book on Tanner is out of date (by a lot)
d. The license checking method is terrible - it randomly checks the
license and if you have 40+ students working on line, I swear the ONLY
traffic is license checking at random times from the tanner tools
running on every station.
e. license server is windows 98 based - very old, and not consistent
with their claim that it is a great PC tool (which in my opinion it is,
it is the license server that is old).
We looked at other vendors, and we use Cadence at the grad level and for
thesis/dissertation work (much more powerful, work station based, etc),
but for ease of delivery, PC based, class room quick up to speed
instruction, Tanner fits our bill.
- Fred J Looft of Worcester Polytechnic Institute
We use Tanner tools, but are currently re-evaluating our tools set, as
Tanner does a lousy backend job. Tanner has bugs, I report them, and
they usually get fixed or noted.
I have not much experience with other layout tools (just Caesar and
Magic). We actually had contact from Cadence and MyCAD in the pass
couple of weeks.
- Mark Jackson Pulver of Silverbrook Research
I am currently using Tanner L-Edit. In my previous company, I used
Mentor IC Station platform. I also performed some evals on Silvaco
Expert (among other tools from Silvaco) and MyCAD. I also evaluate EDA
tools from a new company called Paragon_IC.
My background is analog Power IC circuit design. I am action CAD
manager of the company for the reason that there is hardly any
administrative job for Tanner L-Edit. So you can see, my main job is
analog circuit design (but fairly hand on with L-Edit pro), rather than
a full time CAD manager.
Some of the younger tools are approaching fast close to Tanner L-Edit
but lack of friendly user interface, strong tech support or attractive
price of L-Edit.
L-Edit more or less is an older tool platform that is getting better
and better slowly. It has strong user base, reliable, low cost, very
low maintenance. It may not be suitable for many larger, more complex
ICs, but for the power IC we are making which usually consist of
several hundred devices, medium sub-micro plain CMOS process product,
it seems to serve us well. But from the trend that we are seeing from
more complex IC process with higher digital contents, the capability of
Tanner L-Edit will need to be revaluated.
There is not much to be said about Cadence and Mentor comparing with L-
Edit. There are much better and at the same time, much more expensive.
They are hard sell to us as performance (for our product) vs. price.
My opinion for them is that they are shooting themselves for their own
greatness.
At the beginning of this company (five years ago), I evaluated MyCAD.
I was very impressed with the tools (or what tools promised). But I
was very much put down by the sales attitude and their support. It
didn't present itself as established EDA Company for us even to
consider. I did go back to them two or three years ago, didn't see
their support improve. So I went away.
Silvaco has very attractive tools. We had evaluated their EXPERT many
times. There are many reasons that we didn't choose them. I knew some
of the reasons are no longer true now as the company made many changes
since.
Now since we are very much embedded with Tanner L-Edit. It will take
some convincing reasons and finance support to consider a change. It
has problems -- as you know, I might very well be the biggest
complainer known by Tanner EDA. But it does provide its strong value
for some companies. Overall, my feeling of Tanner is that it doesn't
present as greatest technical solution as an absolute value, but it
presents as a very attractive overall package for us, and hopefully for
many others.
- Tim Yu of Advanced Analogic Technologies, Inc.
What do I like about L-Edit? Nature abhors complexity, and so do I. I
like L-Edit because it just seems to work, and easily at that. The
simple file structure encompasses everything you need in one TDB file.
Importing DRC rules/ external cells, etc. is a breeze (and it always
works). The price is right! We are able to provide a relatively low
cost solution through the use of the Tanner Tools. I like the little
guys. It's a pleasure working with Tanner; the bureaucracy of an
industry giant is not there. Tanner Tools are aimed at "big A, little
D" - this is us.
What don't I like about L-Edit? I don't care too much for design suite
in which L-Edit is encompassed. L-Edit is great, but it's sister tools
are not up to par. The schematic entry (S-Edit) is lacking, which
requires me to hassle with things that would elsewhere be automated.
(I am used to all of the amenities provided by Capture CIS -- P-Spice
A/D.) L-Edit code is compatible with HSPICE, however this no longer a
cost effective solution if you are looking to get away from the rest of
the Tanner suite. The waveform viewer does not have the ease of use or
setup options that others do.
L-Edit in specific...
Good - The cross sectional viewer is super cool. The command line
interface expands the Layout capabilities and is a great idea. I can't
say enough about the file structure and setup simplicity.
Bad - Some warnings in extraction cannot be turned off unless one fools
the program. DRC sets up to run kind of slow (being picky here...) It
would be nice to be able to view shorts.
The Juice - overall, I like L-Edit. My initial ASIC/Layout learning
was on a Sun version of Cadence, which I seemed much more complicated.
Tanner's L-Edit has an advantage in that it is designed as a Windows
program, therefore it acts as a Windows based program which is quite
familiar. L-Edit is a top notch layout tool. In my experience, any
limitations in L-Edit stem more from the partner tools in the Tanner
suite. These limitations, however, fall into an easy trade off called
price which is what really does the talking in our small company.
- Jed Eaton of Healthspex, Inc.
I have used Tanner's T-Spice Pro in the past but haven't had to use it
lately so my memory is less than clear. I can only provide you with
some general feedback on the tool as I am not a power user of this tool
and have some limited experience with it. Although we have access to
more expensive institutionally provided tools, our cost-constrained
projects prevent us from using the higher-end tools, so we are driven
to operate on relatively lower cost PC-based tools.
The biggest advantage to the tool is the fact that it is integrated
with their S-Edit schematic tool (now replaced with ViewDraw). After
creating a test bench in S-Edit and hitting a button in S-Edit's
toolbar, the tool will automatically generate the required SPICE
netlist and start the T-Spice simulation. This is very convenient
since simulations often require multiple iterations and going back-and-
forth between schematic capture and the simulator tools can be very
laborious if the integration between the two is not there. I have not
tried to do the same with ViewDraw as the front-end for this flow.
Circuits I have simulated so far have not been that complex in terms of
transistor count. I have generally been pleased with the tool's speed
as well as accuracy and convergence, often an issue with SPICE
simulators, has never come up as an issue with T-Spice.
- [ An Anon Engineer ]
Some words about Tanner T-Spice Pro:
Downside:
1. Does not reach convergence as easily as (say) Silvaco SmartSpice.
This is its major down fall and reason I don't use it as much these
days.
2. S-Edit does not support buses.
Good points:
1. I like the user interface, nice test editor with key words
highlighted.
2. Able to simulate fairly fast through the use of table models.
3. If you want, you can go for increased accuracy by NOT using table
models, this gives more accurate results, but slows things down (longer
simulation run time). But, it is very nice to be able to choose between
different algorithms. This comes in handy when there lots of flip-
flops and such.
4. Can partition different parts of the netlist to use either table
or non-table algorithms.
5. Has a reasonable plot interface. Kind of primitive, but, not too
bad.
6. Can use current spice model files just like Hspice and
SmartSpice. That is, can used models binned by device size and
understands the ".LIB" spice directive for nested model libraries and
easy ways to use different model corners.
7. If you use their schematic editor ("S-Edit") you can mouse click
on a net to plot it, and, mouse click on a device to see its operating
point information.
8. They do offer the option of using Viewlogic VIEWDRAW as a
schematic capture front end. I don't know how integrated this is the
with the simulation engine compared to S-Edit.
The reason I almost always use SmartSpice is that is reached
convergence more easily and almost never fails! I was constantly
tweaking with T-Spice to try to get it to converge.
Another good point - I feel that Tanner has good tech support. They
always keep track of a bug reports and/or help requests and were always
able to help me out in a day or two.
- Paul Spitalny of Cascade Linear
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