Browse Prior Art Database

Data Streaming

IP.com Disclosure Number: IPCOM000087747D
Original Publication Date: 1977-Mar-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Cormier, RL: AUTHOR

Abstract

The IBM System/370 (I/O) interface may be adapted for high-speed block streaming operation by providing two simple signalling functions on existing lines. One function distinguishes the subject streaming mode from normal mode data transfers. The other function tags and clocks "streamed" data. These functions are described below.

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Data Streaming

The IBM System/370 (I/O) interface may be adapted for high-speed block streaming operation by providing two simple signalling functions on existing lines. One function distinguishes the subject streaming mode from normal mode data transfers. The other function tags and clocks "streamed" data. These functions are described below.

Control and tag lines referred to below and their normal mode operations are described in "IBM System/360 and System/370 I/O Interface Channel to Control Unit Original Equipment Manufacturers' Information", Document GA2269742, file No. S/360S/37019, third edition (September 1974).

A) Indication of Streaming Mode - Normal mode selection comprises the control sequence: "Address In" (from device or control unit) followed by Command Out (from the I/O channel) followed by either Status In or Service In (from the device or control unit). To initiate a streaming mode, the device (control unit) repeats Address In after Command Out and the channel responds with a second Command Out (assuming the channel is one adapted to support a data streaming operation).

B) Streaming Operation - In the streaming mode Mark In and Mark Out signals are used in a DC interlocked manner to tag the beginning of a block of multiple data bytes following on a data bus. The direction of data transfer (in/out) and timing of individual bytes is designated by time-staggered clocking signals on the Service (In/Out) and Data (In/Out) tag lines. The staggering of the clocking signals on the two lines avoids overtaxing the bandwidth capacity of a single line when the byte rate of "streamed" data is maximized.

In the data transfer phase of a streaming mode operation (Fig. 1), the Mark In and Mark Out tags are raised in sequence (by the control unit and channel respectively) in advance of the appearance of the first byte of a block of up to 32 bytes (on Bus In for an input transfer to the channel or on Bus Out for an output transfer from the channel). The sa...