Re: Architectural implications of locate mode I/O

Thomas Koenig wrote:

John Levine <johnl@taugh.com> schrieb:
>

The 709 introduced data channels in 1958 which allowed the CPU to do
other stuff while the channel did the I/O. Wikipedia says the first
I/O interrupt was on the NBS DYSEAC in 1954 but it's hard to see how
an I/O interrupt would be of much use before channels. Once you had a
channel, I/O buffering made sense, have the channel read or write one
area while you're working on the other.

>
Not sure what you mean by "channel" in this context - hardware
channels like the /360 had, or any asynchronous I/O in general,
even without hardware support?

I think he is talking about anything between the PPs of CDC 6600
through that of System 360 channels, where there is enough smarts
in the channel to perform the mundane tasks of shuttling data to
or from the device (DMA) and sending an interrupt at the end
(exchange Jump in 6600 parlance).

>
Sending the next character to a teletype after the user program
fills a buffer and waiting for the next interrupt to tell you it's
ready makes sense, without a busy loop, makes sense anyway.

At that time, TTYs were slow enough to poll (PDP/8) or interrupt
per character.