6 Aug
2015
6 Aug
'15
7:59 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Al Kossow
Sent: 06 August 2015 15:34
To: cctalk at classiccmp.org
Subject: Re: Booting an IBM MP 3000 S/390 System
On 8/6/15 6:16 AM, geneb wrote:
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....
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.
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