From: g4ugm@dave.invalid   
      
   On 21/09/2025 21:31, Lawrence D’Oliveiro wrote:   
   > On Sun, 21 Sep 2025 10:56:33 +0100, David Wade wrote:   
   >   
   >> On 21/09/2025 00:40, Lawrence D’Oliveiro wrote:   
   >>>   
   >>> No IBM Z [in supercomputer rankings]. Not before, not now, not ever.   
   >>>   
   >> No, but these machines are all special purpose.   
   >   
   > My point exactly.   
   >   
   >> The real advantage of the 360/370 etc. architecture was the way it did   
   >> IO. The original channel with its own dedicated processor and 8-bit bus   
   >> running at 1Mhz yielding 8 Mbits/sec was rapid for its era.   
   >>   
   >> Then the use of block mode terminals so the management of input fields   
   >> was all done in the terminal controller. The Mainframe never saw an   
   >> interrupt until a complete form was filled in.   
   >   
   > In other words, mainframes are, and were, all about high I/O throughput   
   > and efficient batch operation. Notice that they are *not* about low I/O   
   > latency, which is important for interactive and real-time work.   
   >   
   > Imagine trying to run a full-screen text editor on those block-mode   
   > terminals -- TECO, TPU/EVE, Emacs ... a few dozen users interrupting the   
   > CPU on every keystroke would probably bring a big, multi-million-dollar   
   > IBM system to its knees.   
      
   You actually can't write an editor that works like that, and you don't   
   need it. IBMs  XEDIT is just as powerful as EMACS in its own way, with   
   the while screen being multiple, editable fields. You have to leverage   
   what you have. I still prefer xedit to teco or emacs.   
      
   >   
   >> I think DEC or was it HP forgot this with the Alpha.   
   >   
   > No they didn’t. DEC machines were all about interactivity, right from the   
   > original PDP-1. That meant low latency, even at the expense of high   
   > throughput. That’s why they were able to run circles around far more   
   > expensive (and complex) IBM hardware in the interactive timesharing   
   > market.   
      
   Then why did they try and sell them as Database Servers or Exchange   
   Server. In fact the converse applies. I well remember sharing a drink   
   with a friend who was rolling out office automation in a big bank.   
      
   At the time the VAX servers he had for All-In-One would not scale to all   
   the users he needed to deliver OA too. So senior managers and directors   
   got all-in-one, but the plebs got IBMs Office Vision because the   
   mainframe scaled better with large numbers of screens, with sub-second   
   response.   
      
   >   
   > Remember machines in the various PDP families were quite popular in lab/   
   > factory situations, doing monitoring, data collection and process control   
   > in real time.   
   >   
      
   We must have had hundreds of 11-s running CAMAC crates, but there is   
   usually no random database access on such systems. Bang the data to tape   
   or floppy disk. Send to mainframe for analysis..   
      
      
   >> I remember looking at Alpha for Microsoft Exchange on Windows/NT. It was   
   >> really hard to justify using an Alpha because Exchange is very IO   
   >> intensive. You couldn't get enough RAID to use the CPU.   
   >   
   > Or maybe Windows NT (and Exchange) were just too inefficient. Did you   
   > compare performance with DEC Unix on the same hardware? Linux was also   
   > starting to build a reputation for offering higher performance on the   
   > vendor’s own hardware than the vendor-supplied OS.   
      
   Thats crap. Exchange is very efficient in terms of CPU use. It just   
   hammers the disks. So how could adding an Alpha CPU increase   
   performance. The alpha that is simply overkill. You could get the same   
   performance, running the same OS on much cheaper, lower performance, in   
   CPU terms boxes. You just need a mirror set for every 250 users...   
      
   If you were Microsoft at the time you wanted Exchange which only runs on   
   Windows so other OSs not an option.   
      
   >   
   >> But we digress, I don't believe the techniques IBM use to perpetuate the   
   >> use of Z would have worked with VMS.   
   >   
   > Correct. VMS, again, followed in that DEC tradition of being primarily an   
   > interactive, not a batch, OS.   
      
   well yes, but it degrades terribly when you get short of RAM and hit the   
   dreaded type-behind. I remember some of my users coming back from a VMS   
   introduction and saying there was no way they were having a VAX how   
   could we get an IBM 4381. I told them and they were very happy...   
      
   Dave   
      
   --- SoupGate-Win32 v1.05   
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