Booting an IBM MP 3000 S/390 System

In many cases more than one! ;-) But more to the point, having a separate processor handing the booting chores frees the main CPU from those tasks. Initialization can be a pain just look at the x86 ISA and the hoops it makes the S/W (BIOS & OS) just to get to the point where the OS can really start it's own initialization! And that doesn't even cover the "magic" that goes on just so that the x86 CPU can fetch the first instruction. As folks have mentioned, a lot of larg(er) system have service processors to handle the booting chores. However, it's more than that. The service processor (as the name implies) is doing a whole lot more than just booting. It is also responsible for running low level diagnostics and capturing the results of hard crashes for later diagnosis. For example, the RS/6000 series, had a service processor. It was even responsible for loading the OS kernel image into RAM. This made the OS's like much easier. Back to the MP 3000. There are a number of CPUs in the box. Two are the most obvious: the SBC running OS/2 and the actual S/390 CPU. However, there is another S/390 CPU in the box as well. It is not visible (at least directly) to S/W. It is responsible for providing the high performance I/O capabilities (like native disk access and making them appear as conventional channel attached devices instead of RAID-5 SSA drives). The OS/2 SBC is there to emulate some of the slower devices (card reader/punch, direct attached 3270s, etc). TTFN - Guy On 8/6/15 10:07 AM, Lee Courtney wrote: