Jim Bohnsack wrote:
> I had an XT/370 PC sometime in the mid-late 80's. It used PAM as it's
> native or default CMS file system if I remember correctly.
> Jim
re:
http://www.garlic.com/~lynn/2006m.html#53 DCSS
http://www.garlic.com/~lynn/2006m.html#54 DCSS
part of the issue was that even tho xt/370 hard disk was single user, it
used the xt hard disk which had 110ms access with block at a time ...
(plus the latency communicating back&forth between the 370 processor and
cp/88 running on the pc processor). The combination of the significantly
slower disk (vis-a-vis mainframe) and CMS being quite a bit more disk
intensive (vis-a-vis applications developed for the PC environment) ...
there was noticeable perception about poor performance.
PAM offers a much better matchup between filesystem operations and
virtual memory paradigm ... resulting in significant efficiencies
(most ibm mainframe operating systems inherited filesystems that had a
significant real memory and real i/o paradigm orientation).
http://www.garlic.com/~lynn/subtopic.html#mmap
CMS filesystem operations had "diagnose I/O" for pathlength reduction
but continued to retain channel program (a "real" memory) orientation. I
had done the precursor to CMS "diagnose I/O" as an undergraduate ...
demonstrating significant pathlength reduction for CMS I/O intensive
operation (which was sort of continuation of a lot of cp67 kernel
pathlength operations I was already doing).
The other place that PAM helped was minimizing real storage requirements
for filesystem operations ... especially evident in environments with
limited real storage configurations. Actually the CP kernel PAM
infrastructure could dynamically adapt filesystem operations to the
level of real storage contention and/or amount of real storage
available. In one high-end (real mainframe) filesystem intensive
benchmark, PAM demonstrated something like 300percent increased
efficiency in filesystem operations (compared to highly optimized
standard CMS EDF filesystem).
XT/370 was significantly real memory contrained for lots of cms
operations. I had done various performance analysis on pre-announce
XT/370 "washington" boxes and found significant page thrashing. When the
information was distributed, I got blaimed for delay in XT/370 announce
and ship while they retrofitted the hardware with larger real storage.
However, XT/370, being a single user system, saw no benefit from the
extensive segment/page sharing capability available via PAM (especially
compared to the limited capability offered thru the namesys/dcss method).
http://www.garlic.com/~lynn/subtopic.html#adcon
misc. past washington, xt/at/370 postings:
http://www.garlic.com/~lynn/94.html#42 bloat
http://www.garlic.com/~lynn/96.html#23 Old IBM's
http://www.garlic.com/~lynn/2000.html#5 IBM XT/370 and AT/370 (was Re:
Computer of the century)
http://www.garlic.com/~lynn/2000.html#29 Operating systems, guest and actual
http://www.garlic.com/~lynn/2000e.html#52 Why not an IBM zSeries
workstation?
http://www.garlic.com/~lynn/2000e.html#55 Why not an IBM zSeries
workstation?
http://www.garlic.com/~lynn/2001c.html#89 database (or b-tree) page sizes
http://www.garlic.com/~lynn/2001f.html#28 IBM's "VM for the PC" c.1984??
http://www.garlic.com/~lynn/2001i.html#19 Very CISC Instuctions (Was:
why the machine word size ...)
http://www.garlic.com/~lynn/2001i.html#20 Very CISC Instuctions (Was:
why the machine word size ...)
http://www.garlic.com/~lynn/2001k.html#24 HP Compaq merger, here we go
again.
http://www.garlic.com/~lynn/2002b.html#43 IBM 5100 [Was: First DESKTOP
Unix Box?]
http://www.garlic.com/~lynn/2002b.html#45 IBM 5100 [Was: First DESKTOP
Unix Box?]
http://www.garlic.com/~lynn/2002d.html#4 IBM Mainframe at home
http://www.garlic.com/~lynn/2002i.html#76 HONE was .. Hercules and
System/390 - do we need it?
http://www.garlic.com/~lynn/2003f.html#8 Alpha performance, why?
http://www.garlic.com/~lynn/2003h.html#40 IBM system 370
http://www.garlic.com/~lynn/2004h.html#29 BLKSIZE question
http://www.garlic.com/~lynn/2004m.html#7 Whatever happened to IBM's VM
PC software?
http://www.garlic.com/~lynn/2004m.html#10 Whatever happened to IBM's VM
PC software?
http://www.garlic.com/~lynn/2004m.html#11 Whatever happened to IBM's VM
PC software?
http://www.garlic.com/~lynn/2004m.html#13 Whatever happened to IBM's VM
PC software?
http://www.garlic.com/~lynn/2005f.html#6 Where should the type
information be: in tags and descriptors
http://www.garlic.com/~lynn/2005f.html#10 Where should the type
information be: in tags and descriptors
http://www.garlic.com/~lynn/2006.html#10 How to restore VMFPLC dumped
files on z/VM V5.1
http://www.garlic.com/~lynn/2006f.html#2 using 3390 mod-9s
http://www.garlic.com/~lynn/2006j.html#36 The Pankian Metaphor
