WOW!!!! $15k DEC PDP-8 CLASSIC MINICOMPUTER SYSTEM DIGITAL PDP8
pkoning at equallogic.com
Wed Jul 6 08:23:01 CDT 2005
>>>>> "Brad" == Brad Parker <brad at heeltoe.com> writes:
Brad> Vintage Computer Festival wrote:
>> In the old days, IBM was stupid and didn't want anyone to learn
>> about their computers. They kept them locked up behind glass
>> walls where one could only drool over them, and only let
>> priveleged people touch them. So
Brad> My experience is the S/360 & 370's machines ran 24x7 and there
Brad> was little time left over for hacking. But if you got to be
Brad> friends with the operators and read all the manuals and what
Brad> source code you could find, you could do some pretty fun hacks.
I've had some operator time in college on a 360 model 44 (running
OS/PCP, which was unusual since most 44s ran an OS specific to that
machine -- it didn't normally have a full 360 instruction set). It
belonged to a nearby grad school, and didn't run anywhere near 24x7.
So powering it on and off was part of the experience.
I had some fun hacks on it. The console wasn't considered a normal
I/O device (it had no name so programs couldn't reference it in the
usual way). But if you constructed a few of the relevant data
structures "by hand" you could read/write it just fine. So I messed
up all the UI conventions by doing exactly that.
The other hack was a switch into supervisor mode from my application
(the WATFOR compiler, actually...) to install a patch into the kernel
to capture an interrupt (some operator panel button). It was really
easy, quite obvious from reading the manuals. I found out later in
grad school that the same security bug was still around in OS/MVS
21.x. Didn't use it there (verified it existed but resisted the
temptation to exploit it).
Lastly, there was the 360 program for reading and printing PDP-11 DOS
formatted tapes... including search by name, something OS/360 could
not do even for native tapes... I wish I still had that program, but
no such luck, not even a listing.
So yes, you could hack those machines if they weren't too large and
you were in the right spot. But I'll agree that I'd grab a PDP-11 way
before I'd be tempted by a 360.
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