[SIGCIS-Members] FC: Oral history of USB

JoAnne Yates jyates at mit.edu
Sat Jun 1 05:05:51 PDT 2019

Very interesting story. Does anyone know why they didn’t try to work through IEEE or IEC to develop the standard?  Was it ever considered?

Sent from my iPad

On Jun 1, 2019, at 3:04 AM, Joly MacFie <joly at punkcast.com<mailto:joly at punkcast.com>> wrote:

Fast Company interview with Ajay Bhatt, Bala Cadambi and Jim Pappas of Intel



AB: Good question. We had looked at it, but the whole goal here was to make it very inexpensive, and at that point, we were trying to solve all the USB problems with two wires. At that point, if you added wires to make things flippable, you have to add wires, and you also have to add a lot of silicon. Wires and pins cost real money, so we decided to keep it as cheap as possible. With serial port and parallel port, there were versions that were 25 pins and 36 pins and so on and so forth. The cables were very thick and expensive. We were trying to solve all the problems. We went in favor of fewer wires. In hindsight, a flippable connector would have been better.

AB: Our goal was to say that this interface should be such that it should work on a mouse and it should also work on a high-end printer or on digital cameras. That’s what we were looking at, the range of products. At one end, we wanted it simple enough, so there could be very low costs. At the other end, we wanted to make sure that it could be scaled and, just as we speak today, we’re running the USB at tens of gigs. The original one was running at 12 megs. We’ve come a long way in scaling.

JP: One of the people we met at Microsoft was Betsy Tanner, and at the time, she was the engineering manager for the mouse. I talked to Betsy and said, “if there ever comes a day that you’re not going to use USB for your next Microsoft mouse, I need to know.” And she says, “okay, that’s a fair request.”

We were designing USB—originally, it was supposed to be a five megabit-per-second bus, which at the time was faster than anything else that normally would come at the back of the PC. It’s not fast by today’s standards, but at the time, it seemed fast. And the reason we wanted high speed was so you could fan it out through hubs, and basically, however many devices would be attached to that single port would be sharing that bandwidth—not necessarily all being used simultaneously, but we wanted it to be fairly robust. Well, Betsy called me one day and said, “Jim, you asked me to call you if we’re not going to be using USB for the mouse. I’m calling you to tell you we’re not going to be able to do it because we have a problem.”

And I said, “what’s the problem?” She says, “Well, 5 megabits is just too fast.”

I said, “For a mouse, we don’t need that much bandwidth, and secondly, I’m really afraid of whether we can pass the electrical magnetic interference specifications. Signals going through a wire become an antennae. Am I going to have too much EMI radiation coming off creating digital noise?”

She said, “we could solve it by putting a shield around it, but it adds 4 cents per foot to the cost of a cable. If I’ve got a six foot cable that adds 24 cents. So I can’t do that. Secondly, if I put a shield on it, a mouse needs to have a simple cable. The cable can’t affect the movement of the mouse, and I’m afraid that if I put a shield, it becomes too stiff.”

So I said, “Betsy, what could you live with?” She said, “We’d be comfortable with two megabits per second.”

And I said, “Damn, that’s just as slow. Give me a week, can you do that?”

She said yes. I came back to the team, and we discussed Microsoft’s problem, and that’s where we actually split it, where we had a high speed and a low speed in the bus. At the high speeds, we brought it up to 12 megabits per second. And then we made the slow speed down to one and a half megabits per second, which was three quarters of the speed that was her maximum.

We saved Microsoft, we saved the mouse. And I think that that call from Betsy saved the program. One of the reasons why USB was so successful is because it hit the cost point that was required. It didn’t add any significant cost to the PC. You can even make the argument that it reduced the cost, over time.


Joly MacFie  218 565 9365 Skype:punkcast
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