-----Original Message-----
From: cctalk [mailto:cctalk-bounces at
classiccmp.org] On Behalf Of Michael
Thompson
Sent: 09 August 2015 13:49
To: cctalk at
classiccmp.org
Subject: Re: Booting an IBM MP 3000 S/390 Syste
Date: Thu, 6 Aug 2015 18:43:53 +0100
From: "Dave G4UGM" <dave.g4ugm at
gmail.com>
Subject: RE: Booting an IBM MP 3000 S/390 System
Actually I remember booting an IBM4381 from cold after we shut it down
over Christmas. Just pressing the Power button powered it up
eventually, but I am pretty sure it took nearly an hour to get to the
IPL prompt. So it did disk drives, then tape drives, then other bits
and bobs. But when it spun up the disks it brought them up one at a
time so the startup surges didn't trip the main breaker. The same with
the tape drives. Then it loaded the microcode into all the
controllers. Then it booted the OS. As we were running VM this last
bit took a few seconds (I think). I do know if VM crashed you screen logo
frequently re-appeared before you had time to think.
Dave Wade
G4UGM
I have done the same on a Honeywell mainframe. After powering up
everything manually the only the mag tape and card reader I/O controllers
had boot capability. Push the INIT and BOOT buttons and it would read and
load tape controller microcode from mag tape, then read and load the disk
controller microcode, then the processor's boot code, and then boot from
disk. It took just seconds for the mag tape part. Getting the front end
processors bootloaded, and getting online communications, timesharing, and
batch processing up took a while.
This system was capable of booting from binary punched cards. We used to
try it periodically just to make sure that this capability worked.
I wonder which system that was. I have also booted various Honeywell L66 and DP300 but
from what I remember you had to power everything up manually. I booted up a newly
installed L66/10 from cards, it was done like that so we could correct the config. On the
4381 it was all done under control of the Microcode in the control processor. Having
written that I now remember that loading the Microcode into IBM mainframes and device
controllers was called IML or Initial Microcode Code....
Dave