( ESNUG 336 Item 1 ) -------------------------------------------- [11/11/99]
Subject: ( ESNUG 331 #1 ) FlexRoute's Hierarchical Approach Questioned
> For FlexRoute itself, our 3 Mgate ASIC with 23 top-level blocks and over
> 7,000 nets had routing runtimes of 30 minutes (for preliminary top-level
> routes during pre-tapeout timing checks) & 60 minutes (for full top-level
> routing with all preroutes and design data for tapeout-quality layout,
> including tuned clocks.) By comparision, our old Compass tools used to
> take 24 hours just to route a smaller sized design!
>
> This massive improvement allowed us to iterate many more times for optimal
> timing and area utilization than we were able to do before.
>
> We iterated on the top-level clock network approximately 50 times for
> the optimal skew characteristics. These changes were made in the
> FlexRoute database (instead of in a layout database), -- so that new
> changes to the netlist for timing and functionality did not disrupt the
> ongoing effort in clock tuning the top-level network.
>
> - Sam Appleton
> SGI Mountain View, CA
From: [ Jumpin' Jack Flash ]
To: "Sam Appleton" <sama@groovy.mti.sgi.com>
Hey Sam,
That was a *really* interesting article you posted to ESNUG 331. I enjoyed
reading your review of FlexRoute. Thanks. I'm glad that I am not the only
one who appreciates the value of ASCII database and file formats!
At my company, we were big COMPASS users (since 1983!!) and so we had a
great deal of infrastructure/knowledge which hinged on being able to "get
in there and hack". Now we have moved over to Cadence (gak!) we feel
somewhat held at arms length from our data.
We, too, have found that Cadence have little to offer in the way of top
level block routers not to mention floorplanning! We shyed away from IC
Craftsman as it was yet another P&R world with yet another database
required yet more techfiles. In the end we managed to get Avanti's
Planet-PL to talk to Cadence's Silicon Ensemble and then used Apollo to do
the top level block routing. I think we may give up on Silicon Ensemble
altogether before too long!
I like the sound of FlexRoute -- I think I had better go and give Synopsys a
call.... (The whole world seems to be turning purple!)
- [ Jumpin' Jack Flash ]
---- ---- ---- ---- ---- ---- ----
From: "Sam Appleton" <sama@groovy.mti.sgi.com>
To: [ Jumpin' Jack Flash ]
> At my company, we were big COMPASS users (since 1983!!) and so we had a
> great deal of infrastructure/knowledge which hinged on being able to "get
> in there and hack". Now we have moved over to Cadence (gak!) we feel
> somewhat held at arms length from our data.
We felt the same way since we went through the same progression. Our last
design used Compass, and I love Compose. Cadence doesn't have anything
similar, which really sucks. Cadence was a big surprise to us since the
tools' DB is binary although they do have DEF, which is a kind of limited
IC language. We did a lot of work with DEF and you can do it that way,
it's just a bit harder. The thing I like about Cadence/Avanti P&R is
fixed connectors -- Compass doesn't like fixed connectors after going
through "adjust topology", but Cadence/Avanti works with fixed floorplans,
which is better for me. We had some real Compass experts around and
we could never get fixed connector placement/adjust to work. Plus Compass'
density is not that great -- Cadence/Avanti are much better on that front.
> We, too, have found that Cadence have little to offer in the way of top
> level block routers not to mention floorplanning! We shyed away from IC
> Craftsman as it was yet another P&R world with yet another database
> required yet more techfiles. In the end we managed to get Avanti's
Exactly what we found. IC Craftsman is a kind of converted tool to make it
try and work for ICs, and it shows.
> Planet-PL to talk to Cadence's Silicon Ensemble and then used Apollo to do
> the top level block routing. I think we may give up on Silicon Ensemble
> altogether before too long!
I think SE and Avant! are probably decent solutions for block-level work,
although they can really stink (I haven't used Avant!s P&R tools yet). If
you're using hierachy though, they really don't work at the top-level at
all. Does Avanti have a top-level floorplanner/router -- they probably
just use their cell-based router at the top-level, I bet... FlexRoute does
have the advantage over cell-based routers because it is tuned for top-level
work in which nets go generally over greater distances than block-level
nets. It also has features tuned to IC work for floorplanning.
- Sam Appleton
SGI Mountain View, CA
---- ---- ---- ---- ---- ---- ----
From: [ There's A Sucker Born Every Minute ]
Dear John,
It's a big no-no to write you at my company. Please keep me an anon.
I've been doing P&R for years. Let me let you in on two foundry secrets.
The first secret is that the average design today is 200 to 300 kgates. We
tell our customers that our average design is 750 kgate to 1 million gates,
because that's what our customers want to hear and what our Marketing
department tells us to say. Reality is 200 to 300 kgates.
The second secret is Avanti easily does place and route on *FLAT* designs
of 200 K instances in 24 hours. YOU DON'T HAVE TO DO ALL THAT HIERARCHICAL
CRAP SYNOPSYS IS PUSHING!!! Sam could have intelligently partitioned his
750 K instance design into four parts by hand and Avanti could take it from
there. No brainer. Kick off Avanti on 4 workstations with lots of CPU
cycles and memory. Come back the next morning. Glue the 4 parts together.
Your final detailed placement and routing is done. FlexRoute and its
complicated hierarchical games are a waste of engineering time and money.
Aart should give a big bonus to the slick Synopsys salesman who sold
FlexRoute to SGI. They didn't need it.
- [ There's A Sucker Born Every Minute ]
---- ---- ---- ---- ---- ---- ----
From: [ Party Like It's 1999 ]
John,
Tell Sam good review. Lots of details. Please ask him whose placement
tools he used. He nixed Avanti and Cadence for routing, but said nothing
about what he used for placement. Did he use Qplace, Avanti, or Chip
Architect? Aristo? Anon. pls.
- [ Party Like It's 1999 ]
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