The Institute for System Level Integration (ISLI) has partnered with an offshoot
from EDA company Mentor Graphics Corp., called Cre8Ventures, to provide access
to Mentor Graphics EDA software to startups for free.
The software will be hosted at iSLI's Alba Centre campus (Livingston,
Scotland) where there is already close collaboration with Scottish Enterprise
and The Alba Innovation Centre to provide support services to companies. ISLI is
a high-level research institute sponsored by four Scottish universities.
Recently, I was working on a (not so big) module which required use of big registers. While synthesizing this module, DC was taking more than 4 hours of time on certain machine and it was becoming very frustrating. Finally I gave up and decided to investigate and address this issue. Following is the experiment information and possible fixes.
Hypothetical Requirements
3 sets of counters are needed to maintain status of various channels (512 channels). Each counter is 12 bit wide and at any given event, 6 counters from a set of counters may be accessed. In verilog, these counters can be declared as followed
reg [11:0] A[0:511];
reg [11:0] B[0:511];
reg [11:0] C[0:511];
There is a combinatorial logic reading these counters by providing two index variables - one is 4 bit wide (16) and another is 5 bit wide (32). Index is calculated by concatenating these two variable (16*32 = 512). Read and write code may look like as followed
input reg [3:0] index0;
input reg [4:0] index1;
output wire [11:0] dout;
input wire [11:0] din;
wire [8:0] index = {index0, index1};
assign dout = A[index];
....
A[index] <= din;
....
Ofcourse, there are 6 access paths for each of the counter set. Since this module has lots of flops (3*12*512 = 18K), DC is taking more than 4 hours to synthesize this module.
Solutions to Improve DC runtime
Do not use "flatten" - This improves a time little bit but not by big amount. In my case, by removing "flatten" command, I improved the time by 2%. Please note, timing of the module is affected by this command and for high performance and small logic, I recommend to keep this command.
Try to replace Registers with embedded RAMs. It improves runtime by 50% easily. But in my case, I could not replace registers completely.
Reduce options for DC to look for. What I mean here is that run time is directly proportional to number of possible arrangements. So for 512 registers in a set, DC will have to look for O(512) in a set and then pick an optimal arrangement. By reducing the options, runtime can be improved but ofcourse, timing optimization is adversly affected. (Less possible combinations to look for.) How to reduce number of combinations?? Look below
Straight way to reduce combinations is to perform logic partition explicitly. For our example, there is array of 512 registers which are accessed by two index variables. We can simply divide 512 registers in 16 groups, each group accessible by index0. Each group holds 32 registers and is indexed by index1. Declaration for this scenario will look like,
reg [11:0] A0[0:31] ;
reg [11:0] A1[0:31] ;
reg [11:0] A2[0:31] ;
reg [11:0] A3[0:31] ;
reg [11:0] A4[0:31] ;
reg [11:0] A5[0:31] ;
reg [11:0] A6[0:31] ;
reg [11:0] A7[0:31] ;
reg [11:0] A8[0:31] ;
reg [11:0] A9[0:31] ;
reg [11:0] A10[0:31] ;
reg [11:0] A11[0:31] ;
reg [11:0] A12[0:31] ;
reg [11:0] A13[0:31] ;
reg [11:0] A14[0:31] ;
reg [11:0] A15[0:31] ;
By Following this methodology, I am able to reduce runtime to little over 70 minutes.
Update: Currently, I have applied above three in my design and able to reduce synthesis time to ~39 minutes. I am still experimenting and will update if anything changes.
It appears that most analysts think that EDA maybe hot again
sometime in late 2007- 2008, when new re-tooling must take place to maintain competitiveness.
The big problem is still design starts—which are still falling due
to the cost of ASIC’s and advances made in ASSP “multiprocessors”,
and FPGA’s.
EDA tools, offering new functionality, may cost more to allow companies to remain profitable because of low volume. For example, NEC announced it's C-2-RTL tool for $300K a piece!
Many IC verification teams use C++, but there are few resources or tools to
help them develop verification environments. Two engineers have launched a web
site with open-source tools that can help, and they've also co-authored a book
on the topic.
Mike Mintz, verification engineer with a large systems company that prefers
to remain unnamed, developed Teal, a C++ class library that adapts C++ to
Verilog and provides threading support. He also created Truss, an applications
framework for C++ verification that sits on top of Teal.
Working to support modeling and verification at a higher level of abstraction,
Jeda Technologies is adding transaction-level assertion to native SystemC
assertion (NSCa), a verification automation tool suite introduced in February.
NSCa is a native SystemC assertion development and debug environment. Its
assertion syntax is said to provide a fourfold to tenfold code reduction over
writing assertions directly in SystemC. An integrated development environment
provides debug, coverage and trace tools, along with editing and make-file
creation.
Until now, however, NSCa supported only cycle-level assertions.
Jasper is offering free verification planning tool, GamePlan. Nice huh! I have not yet played with it so can not offer much. However, check it out... they have user forum/discussion board, documentation etc too!