Path: utzoo!attcan!uunet!bywater!scifi!paladin!beal From: beal@paladin.Owego.NY.US (Alan Beal) Newsgroups: comp.arch Subject: Re: Computer Architecture methodology(really A-series arch) Summary: Answers to my questions Keywords: A Series, B6700 Message-ID: <555@paladin.Owego.NY.US> Date: 17 Jul 90 23:59:06 GMT References: <8533@canterbury.ac.nz> <14279@burdvax.PRC.Unisys.COM> <550@paladin.Owego.NY.US> Distribution: comp.arch Organization: The Design Committee Lines: 110 Following is the response from Barry Traylor to my questions in an earlier posting on Unisys A-series machines. I hope you find it interesting. Alan Beal ------------------------------------------------------------------------ In article <550@paladin.Owego.NY.US> you write: >I used to work on B7800s and A-series machines and I was wondering how >they are doing in the market place and what changes have been made in >the last 3 years. The big iron has been doing OK. The small iron has been growing at about a 20%/year rate (our advertising says that, but our internal numbers confirm it). The stuff still is not "amazingly popular", and they are *mainframes* regardless of their size (block mode datacom, etc). >The most powerful system I recall was an A-17 using >MCP/AS. The A17 just came out a couple of years ago (I think). I was one of the software project leaders for that box, largely responsible for the hardware process switching software and interface specifications. I like the A17. >Is there now a more powerful machine? Yes, but not yet, if you know what I mean. >Have the B1000 users >moved on to the A-3s and A-5s or to another architecture entirely? Don't know. >The 32 bit scheme seemed to be a work around the 20 bit hardware >addressing limitations. Is there any effort to increase the word >length from 48 bits or change the descriptor formats? I was also a project leader for ASD memory management before I moved east. The ASD stuff has been much more successful than we would have ever hoped. There are no immediate plans to increase the data portion of the word, although the tag portion was increased to 4 bits when the A17 was introduced. >I read where >the global table allows a program to address 2**20 objects, each >up to 2**32 words. Is that true? What portion of this is implemented >in hardware and which in software? I also read that the global >table decreased the amount of stack searching for copy descriptors. >How much does this offset the penalty of the extra indirection using >the global table? Lotsa good questions. The current limit (to be increased soon) is 2**20 objects, each of which may be 2**20 words long. If you go to paged arrays, the first number decreases (although memory management gets easier), but the second does not increase (this will also be changing soon). There is a significant amount of software to support the new memory scheme, but the basis is a change in the architecture that makes the old address field a global segment index, so yes, there are also hardware changes. The global table pretty dramatically decreased the stack searching requirements, but did not eliminate them (new architectural changes will eliminate nearly all requirements for stack searching). While the lack of stack searching does somewhat counteract the cost of the indirection, the big gain is in the lack of memory partitioning and the subsequent thrashing. >Any other new hardware features on the A-series >machines? Are they still selling well? There is a new level of e-mode that is being used in a soon to be announced machine. > >I really liked the operating system and the use of compilers instead >of assembly language. However, the Algol compiler did not allow any >complex data types other than arrays. Will this ever change? Ain't algol a bitch! This stuff seems to be continuously going around in circles in the development groups. Apparently there is an implementation of records for Algol that is not generally usable except by SIM. >My >last expereience was on MCP 3.6 and I am wondering how the MCP >has changed since then. Being in the middle of it, it's hard for me to say. The A17 is supported as well as the Micro-A (an A Series processor in a PC box). Lotsa new peripherals are supported. >How well is the semantic database software >being accepted? I don't know. >Any new developments in distributed computing? There is BNAV2. I don't know if that is a new development. It does have some interesting features, however. >Before I leave, does Unisys still provide >the source code for the MCP and other software? Yes, but for an extra fee now. >Are TCP/IP and >other non-Unisys protocols supported? Yes, but other than TCP/IP, I'm not sure. Barry Traylor Unisys Large A Series Engineering barry@tredydev.unisys.com barry@prc.unisys.com (next door)