> -----Original Message----- > From: cctalk [mailto:[email protected]] On Behalf Of Al Kossow > Sent: 06 August 2015 15:34 > To: [email protected] > Subject: Re: Booting an IBM MP 3000 S/390 System > > > > On 8/6/15 6:16 AM, geneb wrote: > > One thing I don't understand - why can't the machine boot on its own? > > Why would IBM design a computer that required another computer just to > > boot it? > > > > > > Main processor microcode is in RAM. Putting microcode in ram and having a > small computer load it was actually pretty common in the 70's and 80's in > larger systems since then you didn't have to manage the hassle of patching > microcode in ROM. >
On a "normal" 360/370/390/Z there are multiple independent I/O processors, called Channels. When you hit the IPL button it is one of the i/o processors that actually loads the OS. On an MP3000 the PC does some of the I/O work so it may be needed to IPL. Most IBM Mainframes from 370 onwards have control processors to manage the main CPU. Some even have smaller mainframes, so one has a 43xx box running VM/CMS as the control box... I believe that Gene Amdahl patented the use of a control processor and IBM paid him licence fees for every Mainframe with a control processor. Of course IBM owned the patents on Virtual Memory so Gene had to pay IBM to use those.... > Apple ended up putting a small TI microcontroller in the G5 because it also > couldn't boot on its own. There was a bunch of volatile state you had to set > up before it would fetch its first instruction. > Lots of newer servers have some sort of control processor. I am used to IBM "X" series which have a control CPU, and on payment of the appropriate licence fee, you can enable remote console support which provides a Java app which can be used to boot the server, power the main CPU up and down, and even map a remove floppy/CD/DVD so you can remotely install an OS. Before anyone asks it has a separate RJ45 jack. As long ago as 2000 I remember Compaq having a RIB board which did the same. I think it is now standard.. Dave G4UGM
