Booting an IBM MP 3000 S/390 Syste

Dave G4UGM dave.g4ugm at
Sun Aug 9 12:38:02 CDT 2015

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Michael
> Thompson
> Sent: 09 August 2015 13:49
> To: cctalk at
> 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>
> > 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....


> --
> Michael Thompson

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