( ESNUG 333 Item 2 ) --------------------------------------------- [10/20/99]
Subject: ( ESNUG 330 #1 ) Users Warn That Cheaper Ambit Really Quite Costly
> We are a small company just starting an ASIC design group. Most of us
> have lots of experience in using Synopsys (I have used it since the early
> 90's). We had Cadence in a couple of days ago and I must say that they
> caught our ear with Ambit. It is hard for us to ignore the price -- but
> I am really scared about leaving Synopsys. Can you give us some advice
> please? An EDA mistake for this company could result in a disaster -- and
> I am scared.
>
> - Paul Borsetti, Lead ASIC Design Engineer
> Enikia Corporation Piscataway, NJ
From: Kelly Fromm <kellyf@packetengines.com>
John,
We went through the same decision pains after many successful ASICs using
Synopsys. I too have been using Synopsys since the late 1980's and version
3.4b, so it is definitely my comfort zone tool.
Our current designs are close to 3-million gates and had we stuck with
Synopsys, we would've been dead in the water. Your design size will have
some influence on your decision, but their are other considerations. (1)
does your ASIC vendor support Ambit, i.e. is there an Ambit library of
cells? (2) what about ATPG? You need a Test-Compiler replacement if you
are all Synopsys. (3) insure that your output format is available (edif,
verilog, vhdl...)
Other than that, we have had tremendous AE support from Cadence on use of
Ambit. The tool works, the logic it builds is functional, the tool runs
incredibly fast, and the scripting is very workable. Scan insertion works
fine, SDF backannotation is a bit slower, but it works, timing analysis is
quick. I still use Design Analyzer to look at logic, but others here tell
me the graphical tool Ambit has works just fine, and has some path tracing
features that are very nice. On the whole, the tool is becoming quite
mature and I expect that we will stick with it. We still hedge a bit by
keeping Synopsys available as a fallback for really tough timing problems.
I haven't had to go back to it yet, however, since Ambit has no problem with
my tough logic at 125Mhz. Synopsys couldn't build an 18-bit subtract in
line with an 18x18 multiply in one clock. At least not without an
additional group of DesignWare. Ambit handled it easily. Hope this helps
with your decision making.
- Kelly Fromm, Design Engineer
Packet Engines
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From: "Joe Kryzak" <jkryz@rocketchips.com>
Hi John,
Last year, because we really need to save money as a start-up, we intially
decided to use Ambit.
Boy, was that a mistake.
Ambit was very aggressive with their price. But without having used the
tool, it was my opinion that we should test drive Ambit, and see what it
could do. I told Ambit that I wanted to have an evaluation copy, and they
were hesitant (and resistive) at first, but finally they gave in and issued
a license.
I created a small state machine that mimicked a typical design here.
I made a Moore machine, with 16 states, created next and present state
logic, outputs, etc. I ran it through Ambit and the output area was larger.
Inspecting the schematics generated by Ambit and DC was the first mistake
for Ambit. Ambit's output was a mess. Nothing was optimized, amature raw
sum-of-products 8-input AND gates stuff all over the place. The DC output
was crisp, clean, and reduced. I added another state machine, and some
counters, and some typical digital designs. Once again, the Ambit tool had
a larger area. I put the screens up next to each other and showed our vice
president the difference, and it was unmistakable. One black mark against
Ambit.
The second black mark on Ambit, and in my opinion the one that killed it,
was the support. Their support staff was bi-polar; some guys were good and
a lot were quite bad. It was random who I'd get on each call.
For example, we ran into the obvious situation that our cell provider didn't
have the Ambit libs. Ambit provided them with a their version of a library
compiler and after 4 months I got Ambit libraries. This wasn't 4 months
waiting; it was 4 months of many emails back and forth. (This is how I
discovered that the Ambit support staff, one the sale is done, is not as
conscientious as Synopsys.) It sucked trying to clean up Ambit's mistakes.
An example problem: one of the Ambit symlibs ( symlib was the name of the
symbol lib) I was sent contained bogus info -- it was tarred incorrectly.
But yet, they insisted that it worked on their side. When I found what the
error actually was (note *I* had to find the error (which took 4 working
days!)) they finally had to admit that the problem was theirs, and finally
I got the corrected lib. Another problem was that the library didn't read
in correctly. I had to download a new version of the Ambit tool to get it
to work. Then there's my horror story of having to debug Ambit vs. Ambit.
The Ambit support staff and I both using the same version, same netlist,
same script -- we got very different results. I gave them a 2,000 gate FSM.
The Ambit support guy said, "I only see 17 inverters in your design." I
spent two weeks on that issue and then had to just drop it because I happen
to design chips for a living, not debug Ambit for a living.
These were slap-in-your face problems, and it took 3.5 months. What if I
discovered a subtle problem, how long would it take? This was my breaking
point. I decided against Ambit, because of the massive time loss in
dealing with any problem that came up.
However, some things I liked about Ambit was its interface. I believe it's
better than Synopsys. Ambit's documentation is also less verbose, which I
prefer. I'm hoping Ambit will force Synopsys to eventually lower their
prices. ( And hopefully, my Design Analyzer licence will still work after
that comment! :^) )
If there are any "die hard" Ambit fans out there, I'm sorry to disappoint
you. I call them like I see them, and I gave Ambit too much of my time.
- Joe Kryzak, Project Engineer
RocketChips, Inc. Minneapolis, MN
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From: "Gregg Lahti" <gregg.d.lahti@intel.com>
Hi, John,
It scares me to think that cost-conscious CAD managers with almost no
accountability to a project schedule can affect my job so much. When you
buy an EDA tool, it's not just the purchase of the tool that makes it work
-- it's the bug fixes, AE support, and new revisions that mean the most.
In my experience this is where the rubber meets the road when you need to
get your project done and the tool is blowing chunks. In comparison of
Synopsys to Ambit, I'd much rather pay more for a tool that I KNOW works
95% of the time and comes with decent support. (Granted, DC is expensive
and competition for Synposys hopefully will keep the price down and out of
the anti-trust/monopoly courts).
I've also had great success on the last two projects I worked on when we
decided to use new Synopsys tools (BC, MC, PrimeTime). Our local AE support
was above anything I've seen stumble out of Cadence. Sometimes the tools
broke (doesn't all EDA?), but the fixes/work-arounds were quick which didn't
impact schedule.
Price isn't everything, or we'd all be driving Yugos.
- Gregg Lahti
Intel Corp Chandler, AZ
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From: "Mangesh Pimpalkhare" <mpimpalk@wharton.upenn.edu>
Hi, John,
While at NeoMagic, we evaluated Synopsys and Ambit head-to-head in a large
design, and finally chose Synopsys. I worked as a design manager and
our group was faced with the challenge of planning for our next generation
laptop graphics chip that was going to be much larger (about 2.5x) than our
previous chip. We wanted a reliable synthesis solution, which could give
us the best quality of results. We wanted to compare Synopsys' quality
of results with Ambit's, making sure it was as close to an "apple-to-apple"
comparison as possible.
People often compare synthesis results in a quick and dirty fashion, missing
details like wire load models, synthesis scripting methodologies (top-down
vs. bottom-up, or a mixture of the two), total negative slack vs. worst path
slack, design rule violations, etc. We also used this opportunity to
overhaul our somewhat outdated synthesis methodology. This helped us
realize significant area savings with better timing.
Choosing Ambit would just have introduced significant risk with no
commensurate benefits.
I would also like to point out that switching EDA tools, especially unproven
tools, has significant risks associated a with an impact on the layout
methodology, timing convergence, library development, QA, and training.
Each of these could cascade and eventually impact project schedule and
time-to-market. Living with known bugs is one thing, getting surprised with
the unknown is something else. Synopsys certainly isn't without bugs, but
we had a good understanding of how to get around them, having put several
designs that were synthesized using Synopsys into volume production.
The bottom line is, if Ambit would have been measurably superior in timing
and/or area relative to Synopsys, we would have weighed those benefits
against the risks of going with an unproven (compared to Synopsys, Ambit
has negligible amount of silicon in volume production) tool. In the end,
we got better results with Synopsys, so sticking with Synopsys was a real
no-brainer.
My final warning to anyone doing synthesis comparisons: the devil is in the
details! Make sure you are comparing apples with apples!
- Mangesh Pimpalkhare, MBA Candidate
The Wharton School of Management University of Pennsylvania
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From: "Gene K. Chui" <gchui@cisco.com>
John,
We evaluated both Ambit and DC and we decided to go with DC. From the
technical point of view, DC had about a %15-20 faster runtime with both
tools meeting timing. We were also concerned about the risks of using a
new tool that did not have many tape-outs, while DC has done thousands of
tape-outs. The Synopsys support was also much better than Cadence's
post-sales support and we liked their future roadmap of integrating
synthesis with the physical tools.
While Ambit did have some nice features, it was clear that DC was better
technically with far less risk then Ambit.
- Gene Chui
Cisco Systems San Jose, CA
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From: [ Microprocessor Slave ]
John:
Please keep my absolutely anonymous as [ Microprocessor Slave ]. This is
in reference to Paul Borsetti's question in ESNUG 330 #1.
We looked at Synopsys & Ambit sometime back, and decided to pick Synopsys.
We already had an existing flow with Synopsys, and wanted to look at Ambit
because of the promise of significantly better results.
The initial Ambit results looked good, and were better than our previous
Synopsys results. But once we got in touch with the Synopsys AE and
switched to a more recent version (98) of Synopsys, the Quality of
Results were better than Ambit's both in terms of runtime and area.
However the performance of the tool wasn't the only aspect we considered.
Methodology issues, training, reliability, and risk are also important
things to be considered. For example, we have working links from synthesis
to layout and backend tools, as well as ECO flows etc. There are standard
interfaces, and we also have lots of custom scripts. The current Synopsys
flow we have is proven and tested ... moving to another tool would
potentially be a huge time-sink in engineering time with uncertain results.
We concluded that unless Ambit had significant gains, it would not be worth
the risk since design cycles are very tight.
While as a solution Synopsys was better, there was one aspect to Ambit that
was somewhat interesting to us then, which was that Ambit was a startup. We
thought that they might be more responsive to our requests, and turnaround
custom changes faster. When Cadence acquired them, that stopped being a
plus for them !
- [ Microprocessor Slave ]
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From: Mike Davoudi <mdavoudi@picoturbo.com>
John,
We develop both high speed (300 MHz) and low power (less than 0.4mW/MHz)
synthesizable micorprocessors. Synopsys synthesis is critical during both
pre-layout and post-layout design. The convenience of an all-in-one
synthesis tool allows us to dedicate more time on the design-implementation
phase and less on the back-end flow. Once our RTL is complete the rest is
push-button. DC allows a simple script to run over night and prepares a
netlist and information about the netlist for the designer the next morning.
Synopsys has the right idea of creating an all-in-one design tool. It
eliminates complications and saves us time.
- Mike Davoudi, ASIC Design Engineer
PicoTurbo, Inc. Santa Clara, CA
---- ---- ---- ---- ---- ---- ----
From: [ Echoing From Within Texas Instruments ]
John,
I would like to submit this article for ESNUG. I would request to be
anonymous on this posting. Thanks.
Texas Instruments has gone through two major evaluations of the DC and AMBIT
synthesis tools, in the last one year or so. In both the evals, the DC
results are more promising. Looking at the benchmark results, I've found
improvements in both run-time as well as the quality of the synthesized
netlist (area reduction and faster circuits) for DC.
Additionally, a common integrated tool set for critical steps like datapath
synthesis (Module Compiler), static timing analysis (PrimeTime), timing
closure (links-to-layout), and equivalence checking (Formality) helped our
designers a lot.
- [ Echoing From Within Texas Instruments ]
---- ---- ---- ---- ---- ---- ----
From: sriram@neomagic.com (Sriram Ramamurthy)
Hi, John,
I'm a design manager in NeoMagic, and our company had looked at synthesis
alternatives seriously sometime back and decided to stay with Synopsys.
The point tool comparison between DC and Ambit should be just one aspect to
be considered. As a point tool, DC did give us better Area and better
Timing for the same designs. (For someone doing a high volume part, these
can translate to significant savings that directly affect the bottomline.)
There are also other more important factors to be considered.
Flow issues are very important, and we have working flows with Synopsys with
our back-end tools, verification tools etc. We know that if we need to add
other tools to the flow, they will support Synopsys tools, and that's very
important. It's also a lot easier to find engineers conversant with
Synopsys tools, otherwise we run into training issues with any new tool.
We have enough risk in our projects. It helps to know that the synthesis
tool has been tested extensively by others over the years, and is going to
be tested by thousands of others currently.
This minimizes the chance of us finding bugs ourselves the hard way.
One other suggestion: if you are already a Synopsys user, consider giving
your methodology and scripts a "tune-up" from time to time. We did that
with the Synopsys AE's help, and realized significant improvements in the
performance and Quality of Results.
- Sriram Ramamurthy
NeoMagic Santa Clara, CA
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From: [ Intel Inside ]
John,
I wanted to give you some feedback on the abmit discussions. Please keep
me anonymous.
When CAD mgrs pick point tools based mainly on cost, the results are
sometimes a hodge-podge of cheap point tools strung together with Perl
scripts to make a design flow. This is not always the best way to get
a best-in-class design methodology.
Ambit may have a decent synthesis tool that is worth looking at, and maybe
SYNOPSYS will be forced to discount DC a little more. But just having a
good cheap synthesis tool does not make a good design flow.
Synthesis is not a simple part of design, and knowledge of DC scripting will
hinder Ambit's acceptance -- but cutting the price won't really help them.
Our engineering costs far outweight EDA tool costs.
You need the other tools in the flow to work together and you need customer
support. I've found that Synopsys gives first-class customer support to us
at Intel. Their AE's are first rate & they are responsive to bugs we find.
Also, Synopsys has a very complete set of tools from behavioral/datapath
synthesis through static timing and layout ECO flows that has a proven track
record of working well with DC. Ambit is new stuff with absolutely no
track record of even passably working with any these other EDA tools. Saving
$50 K up front doesn't make up for the hundreds of thousands of dollars in
engineering costs and delays, I'd pay trying to make Ambit work.
- [ Intel Inside ]
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To: kegger@morphics.com <kegger@morphics.com>
John,
I am a ASIC design manager at a start-up. We are also in the process of
building an ASIC team for implementation of our early products. Like most
other start-ups, finances are extremely important. With EDA tools consuming
a significant portion of our overall budget, we must make our decisions
wisely because there is no second chance for us. Because of this, I you
need to review the fundamentals when making a decision on key implementation
tools such as synthesis. I tend to go straight to the bottom line:
BOTTOM LINE: Get a quality product out the door in a timely fashion.
This means:
A. Proven tools with proven flows
B. Available IP (both synthesizable and target library)
C. Available expertise (i.e. people who know how to use it)
D. Proven foundry libraries
While Synopsys isn't exactly cheap, the loss of revenue associated with a
slipped schedule is far more important. It can sometime even be fatal.
Paying more for tools which will *definitely* deliver and are widely
supported (both by people you need to hire as well as with vendors whom
you need to work) is not a bad decision in my book.
Having said this, however, I like to encourage competition. Thus, if
you are not in the critical path to your company's overall success, then
evaluating any new technology is a reasonable thing to do.
We don't have that luxary. Our designs have to work the first time around.
Best of luck on your decision,
- Keith Rieken, VLSI Manager
Morphics Technology Inc. Campbell, CA
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