On Fri, 31 May 2024 09:49:09 -0400, Phil Smith III wrote: >I remember hearing that some Amdahl 370 clone was upgradable by cutting a >wire. Anyone else ever hear this? Can't find a cite on the web. > As I heard it, they were always delivered with memory fully populated but partly disabled. The upgrade enabled it.
And the CDC 6603 disk had a performance enhancement. Originally after positioning heads it waited for a fixed time for vibration to damp. The enhancement was to read immediately and continuously until the data wers reliable. The 709x always had an undocumented STore Zero instruction by a fluke of circuit design. It was later introduced as an option. There was no Illegal Instruction fault detected. Some microprocessers were reported to have useful undocumented instructions. The conjecture was they were design features that failed design test. Use at risk. And 5% and 10% resistors come from the same manufacturing process; selected by test. If you buy the 10% you are practically guaranteed to get none within 5% of spec. My employer ordered evaluation samples of a floppy disk drive and observed that they performed at higher than specified density, designed and marketed to that, but discovered that the production units were not so good. All citations needed. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
