LVDS and terminators

Tak Asami asami at
Wed Oct 4 16:27:50 PDT 1995

Well, Jim.
I admire you for being so good at making everyone else feel so inadequate
with only an over-simplified half-a-theory.  I should learn how to do that
as well as you do.

But seriously.
You are not telling me that I should wait for 6 months to buy my 4GB SCSI
drive, since it'll be free by then?  Well, I guess not, or both you and I
are out on the street and can't afford to buy one.

Being in the business of selling the chips, I'd love the idea of everyone
having to buy more expensive chips, that can do everything.
But despite high cost of inventory, people do produce multiple products.
Why?  Mostly, because the cheapest products (i.e., highest volume products)
always want to be cheaper, and don't want to carry excess baggage for the
more expensive, lower volume products.

You should talk to our customers more.  Unfortunately, they want to buy
cheap chips for cheap applications, and they want to buy cheap chips for
EXPENSIVE appllications.  Alas, I am not good enough to supply them with,
for example, a single chip target device that does Fast-40 LVDS and Fast-20
single ended and have the buffer bandwidth wide enough for 80MB/sec (plus
whatever your media rate and CPU access) for the same price as if we just
do Fast-20.  So they'd want to buy Fast-20 chip for Fast-20 applications,
even if we have a whiz-bang fast-40 single chip.
Well, that's also somewhat oversimplified, strictly not true, but I'm not 
giving away my trade secret.

And your point about inventory is well taken. But that doesn't seem to
directly translate to something having to transform from SE to LVDS and
back in an instant notice.  It seems to me it's more like the installation
stays one setup or another, but you don't have to repurchase all your drives
when you upgrade.  Otherwise, why the hell are you doing with expensive (it's
a relative term, however) twisted-pair flat cable with teflon insulator?
Or is there someone who sells the cable that transforms from A-cable to 
Fast-40 cable depending on the state of diffsens?

Yes, we do sometimes engage in practice where same silicon dies are put
in different packages with different part number, and with some feature
differentiation, priced differetly ("the price has nothing to do with
the cost" - biz 101).  But that is of no concern of NATIONAL STANDARDS
that we are talking about here....

> Obviously we will NOT be buying terminators that cannot do both LVDS 
> and SE for our drives (big hint to terminator manufacturers everywhere),
> since that would defeat the purpose of the SE/LVDS in the drive.

You are touching upon the exact point I was trying to make.
If you studied the terminator requirement for LVDS and compared that to
single ended, you can easily imagine that your "switchable terminator" 
is not *A* terminator but two terminators in a box.
So you were talking about the cost???  So you or your customer is ready to
spend extra for the do-it-all terminators and do-it-all drives even though
you know you'll be staying on a mere single ended fast SCSI, because you 
want to keep your CDROM drive want to reserve the right to go Fast-40 one
of these days? 

Enough of that.  I just said it to frustrate you, did I succeed?

I'll get to the point before I completely lose it.

We need more defined migration path to strategically place the Fast-40.
It indeed is the main theme of the upcoming Fast-40 marketing meeting
that you are hosting.
I don't think what you suggested even begins to answer the question,
and I believe I asked a valid question.  I'm waiting to hear more 
questions like that, so our marketing reps can start thinking about them.
                           Tak Asami
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