Browse Prior Art Database

Address Trace Compressor

IP.com Disclosure Number: IPCOM000078120D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Fuegel, EF: AUTHOR [+3]

Abstract

This is a method of obtaining a trace of an address stream being generated by a high-performance computing system, where the sequence of address's presented to the memory address register cannot be recorded in real time on conventional tape drives, because the data rate is too high. This method reduces the data rate without significant loss of information relating to memory segmentation, by capturing a version of the computer address stream which, although not exact, is statistically similar to the exact version. The version departs from exactness due to: (1) congruent class subsetting; (2) sequence sampling; and (3) address compression.

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Address Trace Compressor

This is a method of obtaining a trace of an address stream being generated by a high-performance computing system, where the sequence of address's presented to the memory address register cannot be recorded in real time on conventional tape drives, because the data rate is too high. This method reduces the data rate without significant loss of information relating to memory segmentation, by capturing a version of the computer address stream which, although not exact, is statistically similar to the exact version. The version departs from exactness due to: (1) congruent class subsetting; (2) sequence sampling; and (3) address compression.

Data compression achieved through sampling by class refers to the segmentation of memory so that the address stream for a subset of all segments can be monitored.

Data compression through address compression, refers to a technique of deleting repeated references to pages already in the directory of the monitored address stream. The number of page addresses which the directory is capable of holding determines the amount of compression available through this technique.

Data compression by sequence sampling, refers to a sampling of sequences of addresses by filling buffers with the sampled address stream while, at the same time, writing the buffers out to tape. Since the writing operation is slower, the buffers will eventually fill. At that time, the sampling sequence will be ended until the write operation has unloaded the buffers. At that time, sampling the next sequence of addresses will be begun. With this technique, long sequences can be recorded out of short buffers when the buffers are initially empty and the data rate out is close to the data rate in, and when the buffer is driven until it overflows.

Referring to the drawing, the 16 bits addressed from the memory address register 1 are gated to a manually operated switch 2, which selects up to 7 class bit positions. Bits to the right of these class bits are ignor...