Ask HN: Questions for two 40 year IBM Mainframe repair and programmers • Hacker News Board

Re: Ask HN: Questions for two 40 year IBM Mainframe repair and programmers

#41

Post by elsherbini » Fri, Dec 29, 2023, 2:12 PM UTC

bjornlouser wrote: post #9

Did either ever come close to leaving the field? If so, what made them want to quit tech?

I never considered leaving my IBM Field Engineering job. The job was rewarding and gave me a great sense of purpose; however it was very stressful and had a lot of high expectations. With the 360 line of computers the field was flooded with engineering changes (ECs) to be installed and IBM eventually hired part time people just to install ECs. The ECs eventually fixed the many problems with the 360s and the job demands settled down to more normal.

Re: Ask HN: Questions for two 40 year IBM Mainframe repair and programmers

#42

Post by norwayjose » Fri, Dec 29, 2023, 5:44 PM UTC

elsherbini wrote: post #31

1920musicman wrote: post #11

Would love to know whether security was a concern at all on those systems (eg industrial espionage, internal program meddling for the purpose of tricking auditors, etc). And if yes, then what are some interesting stories about investigating and resolving security issues. Thanks for doing this!

Hacking was not a problem in the early days of computing as there was no internet and computers talked to each other over dedicated telephone lines. - Grandfather

In the late 1970s, we used dial up modems (the kind with the klunky acoustic coupler) to dial into Honeywell's response center to close out repair calls. I also discovered they had games on the response center computer and was able to entertain myself on quiet night shifts by playing Adventure and Star Trek on a TI Silent 700 terminal.

Some of the mainframes we servicced were also connected to ARPANET which provided networked access to university and various government agencies. I know there was an ARPANET worm around 1980. Not sure if there was hacking prior to that.

Re: Ask HN: Questions for two 40 year IBM Mainframe repair and programmers

#43

Post by elsherbini » Fri, Dec 29, 2023, 10:36 PM UTC

norwayjose wrote: post #40

elsherbini wrote: post #32

Earlier quoted context omitted.

I do not remember any transistors being inside the core house but sometimes the welds inside the house would break loose and if you could find the broken weld you could resolder it. IBM core units did not have spare positions. Sometime the entire core house would have to be replaced. - Grandfather

Thanks. That's interesting. I've only seen the outside of IBM mainframes in the few computer rooms which had both types of machines.

I think my most challenging diagnostic problem was a channel hanging the system. I used a 360 I/O channel test box that connected to the channel and when a error or hang condition would occur it had recorded the last several instructions and the channel responses to those instruction. IBM sent a factory engineer to the site and it was determined that a test I/O instruction to a 3271 was generating a device end status when it should not generate any new status. The fix was a EC to the wiring of the 3271. My most unusual repair was not in the maintenance manual. One morning about 2 am I had a bad 12v power supply in a disk controller unit. I asked the customer to bring me a 12volt car battery. I rewired the 2841 to the battery sitting in the floor beside it. The 2841 powered up and ran for about 15 minutes before it started getting disk read errors. I asked the customer to bring me a battery charger which I connected to the battery. The computer ran two days with the battery supplying the 12v until I could get a power supply. Sometimes experience and good luck are the troubleshooters best tools. In 1988 I was in China helping the Chinese with their computers and received a call from The Bank Of China as their system was down and they had closed the bank because of it. My assistant Chen Wei and I walked into the computer room and I looked at the console. The console showed a MPX channel error. I looked around the computer room and saw several sections of the raised floor were pulled up which indicated the Chinese service company had been moving boxes around. Due to past experience I knew the buss and tag cables could be switched and would cause a MPX channel error. The first box I checked had the cables switched and Chen Wei switched them correctly. Everyone in attendance thought I was a true computer expert but it was experience and good luck.