Case
Study 1: The Jurassic Chip
 A hapless engineer
named Jones was bemoaning his latest assignment. "Why me?"
he lamented. "They want me to reinvent a very old wheel."
His cellmate
Bob was almost asleep when the tirade started. "Hey! Not
so loud!" he barked. "Just because you're miserable
doesn't mean I have to be too!"
Jones
shot back, "Well, what am I supposed to do? I wasn't hired
to do archeology!"
"What
are you whining about?" Bob asked.
"The
company has this system that's still being produced, even though
it's not much better than an abacus. They have chips on the board
that they can no longer purchase, at any price," Jones explained.
"The inventory is like a ticking time bomb. They want me
to reintegrate the entire thing into an FPGA."
Bob countered,
"So what's the problem? You get the design files and talk
to the original engineer, and reintegrate ­ no big deal."
"Oh,
really? I think the design files were partially destroyed in
the San Francisco earthquake ­ you know, the 1906 one! The
only documents I can find aren't the final ones. The actual implementation
is a mystery. There is a one-page, coffee-stained data sheet
describing the 'state of the art' 3 micron NMOS process used
in fabrication. The only thing I can get is test vectors."
"What
about the engineer?"
"He
took early retirement. The last anyone heard he lived in a commune,
growing organic kumquats."
"It
sounds like all you have is test vectors and a chip," chided
Bob. He thought a minute, which also happens to be the length
of his attention span. "I heard about this device... What
was it? Hmmm... Oh well, it's just about time to punch out."
"What
device? What are you talking about?" Jones insisted.
"I've
really got to go," said Bob. "I've got to get home
to sweep my garage."
"Don't
move!" Jones was getting agitated. "If you leave, I'll
quit and they'll stick you with this project! Now tell me: What
device?"
Bob sat
down again, hiding the delight he felt at torturing a colleague.
(He had all the requisite skills to move up into management.)
"Well, I think it's called PinPort. It's supposed to connect
a chip to a simulator. If you have vectors, then you can apply
them to the chip."
"I
don't want to test it ­ I want to replicate the logic in
readable, understandable Verilog source code so I can synthesize
it," Jones declared.
"Well,
what's the first step?" countered Bob. "You need to
get a test bench that you can rely on as accurate, accurate to
the silicon, not the nonexistent specification. This PinPort
thing allows you to do that. Then you can take what you've got
and create the RTL code, all the while testing it against the
actual chip."
"Well,
yeah, I guess that would be a big help. Now tell me it costs
a lot, and I need to spend 3 months in training just to turn
the power on."
"Absolutely
not, but you should check it out for yourself, and let me go
home."
Later
that week...
Jones
was in the lunchroom with his feet up on the table. Bob noted
this with some trepidation. "What are you doing? I thought
you were in the hot seat."
 Jones casually
mentioned that he had gotten a product called PinPort, and his
problems were over. "This thing is great. I wrote a simple
Verilog model to interface to the chip. Next I applied the test
vectors, and they actually stimulate the chip, and the test passes.
Then I had to get some coffee, and latched onto our new intern.
He's writing code for the replacement RTL. After he writes a
little, he runs the test. It passes, or not, the code is good
or not. All I need to do is wait a while, and he will have this
thing done. I was thinking about taking a vacation."
Bob was
fuming. "Hey, that was my idea ­ I should take the vacation.
And who said you could use our intern for actual work?'
"Sorry,
but now that I have the PinPort, life is good again. I don't
stay up at night wondering if the silicon will be the same as
the test. I know I can get this done right the first time,"
Jones gloated.
"It's
not you ­ it's the intern, and my great idea about using
the PinPort!" shouted Bob.
"I
can't talk right now, I have my review coming up. I should be
getting a raise big enough to cover my stock options." Jones
walked out.
Bob went
back to their cubicle and promptly set Jones' desk on fire. |
