Random Access Tape 2446

'sqrfolkdnc' worte, in part: Of course the LGP-30 had main memory AND the accumulator on DRUM, and addresses were NOT sequentially buttigned.

While I never worked with an LGP-30, though I helped get replacement systems for it up and running. In 1965-66 Pittsburgh Plate Glbutt Company replaced the LGP-30 in each of their 5 paint plants with Univac 1050 systems (24 to 32 K 6-bit core memory.) I remember discussions of placing data and instructions to avoid rotational delay. For the 1050 replacements we had severe memory limitations even with the much larger size; we used very complex instructions (that took a very long time to execute) to compress the code. The main I-O was 800 bit-per-inch tape; even sequential access was slow.

Phil Weldon

Of course the LGP-30 had main memory AND the accumulator on DRUM, and addresses were NOT sequentially buttigned. A good programmer located his working storage so that it could be most often fetched in the same revolution as the instruction, then fetch the next instruction wihout wasting a whole revolution of the drum. There was a chart showing what memory locations could be accessed from an instruction at any location, without losing a revolution. It had 4096 words of memory, IIRC. Don't modern tape drives have multiple tracks, going to the end and back multiple times, so if you want to get to something 95% through the complete linear image, you only have to scan down one track part way to get it, not through 95% of the data?