Re: PS/2-to-USB adapter - why does this work?
- From: et472@xxxxxxxxxxxxxxxxxxx (Michael Black)
- Date: 3 Jan 2007 17:28:15 GMT
George (gh424NO824SPAM@xxxxxxx) writes:
I see this for about $6 at Newegg:
http://www.byteccusa.com/product/adapter/bt-2000.htm
It lets you connect both a PS/2 keyboard and mouse to one USB socket
on your computer (for laptops which have no PS/2 ports).
Just looking at it, and with the price being so low, it appears that
this may just be straight-through wiring, with no processing or
logic circuitry at all.
If that's true, then I'm confused. I'm no expert on either the PS/2
or USB protocols, but I just always thought they were not
compatible, as well as being pretty complicated (well, USB, at
least). Particularly if, as is the case with this adapter, you
parallel two separate devices at the input. I've checked on my old
desktop, and the two PS/2 ports are not paralleled - only the power
and ground pins are common.
So I guess I'm saying that I'm surprised this works. Does anyone
have an explanation, or even a link to an explanation?
I just got a new laptop, and just assumed I would need to buy new
USB keyboard and mouse stuff for those times when I just need to go
faster than the laptop's touchpad and keyboard will permit. But
apparently not. And I really really really like my old keyboard and
mouse. So this is officially nifty if it works.
This is hardly a design question, but you forget that design isn't just about
making something, but often about making something cheap.
When something sells well, the manufacturer can lessen their cost
by buying in quantity and going to custom components that result
in lower manufacturing cost. They can then translate that to a lower
price to the consumer.
That lower price increases demand for the item, which can in turn cause
another iteration in design that drops manufacturing costs again, which
drops the selling price further.
The history of electronics has always been this history. VCRs were out
of sight price wise when they first went on the market, and they were
made with many off the shelf components and as a result were big and bulky.
But as consumer demand increased, manufacturers were able to use higher
integration components, which brought prices down, and so on. The
price drop seems even more spectacular with DVD players.
So your equation is missing this. You don't need to seek some false
path to understanding of what's going on in that device, you simply need
to know that what's inside has now been compressed down to what amounts
to a blob of epoxy over a bit of silicon and the cost of designing
such high integration is spread over a large number of the item being
sold.
Now, if this had been soemthing that few people would be interested in,
a low price might indicate something that is making do with some wires,
because demand could not reflect a low price.
Mice and keyboards aren't particularly simple devices, floppy drives
either, yet all can be had for a song now, while they cost hundreds
of dollars a couple of decades ago.
Michael
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