martillo@ATHENA.MIT.EDU (11/23/87)
Before I receive hundreds of letters about my faux pas with the mailer, I am aware of the mistake and apologize for it. Since I am mailing out this letter, I may as well may it somewhat useful. I noticed arcnet being discussed here. Now my friends at Clearpoint use arcnet networking cards with vme bus interfaces for some sort of distributed memory testing. After seeing arcnet mentioned in this newsgroup, I have become curious. Where does arcnet come from? Who uses it and why (instead of some other networking scheme)? What are the achievable data rates? Where can I get literature on arcnet? Yakim Martillo
socha@drivax.UUCP (Henri J. Socha (7-x6628)) (11/24/87)
Answering your questions even as I read them: In article <8711222235.AA13789@ARES.MIT.EDU> martillo@ATHENA.MIT.EDU writes: >I noticed arcnet being discussed here. Now my friends at Clearpoint >use arcnet networking cards with vme bus interfaces for some sort of >distributed memory testing. After seeing arcnet mentioned in this >newsgroup, I have become curious. > >Where does arcnet come from? It was developed at Datapoint Corp. of San Antinio Texas in 1976 by members of the Advanced Product Development (R&D) group I was a memeber. Datapoint (and people in this group) also architected the "Intel 8008", the first dBase type of programme (that I know of), the 2nd PC (IBM's 5100 was first), one of the first glass TTYs, etc. (But enough of this.) The ARCnet hardware and protocol was designed by one Engineer with the help of two techs. and about 3 other people who discussed it and gave advice/suggestions. The limitations of board (TTL MSI) space generated some of its idiocyncracies for example the DID is transmitted twice on the wire. The changes to Datapoint's DOS similar to what happens/happened when you go from PC-DOS 2.x to 3.x was done by one individual. This DOS used a similar similar system to the NET USE of PC-DOS call MOUNT. By the way, remember that we are talking about a networking OS in 1976! >Who uses it and why (instead of some other networking scheme)? It was first used inhouse to connect multiple Datapoint machines together so that production/purchasing/etc. could access common databases and allow more that 10 DataShare users access to one database. The only other network known (by us in R&D) was Ethernet (the original 3MegaBaud XEROX one). It was decided (demanded) that a system be used where assured transmission within a maximum time be used. The concept of CSMA/CD (Ethernet, etc.) still is revolting to me. ARC has very simple installation using what I call a connected star configuration. And is VERY robust in that most anything that happens to the cable (connections/disconnections/wiring changes) can be done on a live system with reconfiguration handled automatically by the hardware. I.E. as long as your node doesn't need something now disconnected, your node does not even know that the break occured. The robustness, its reasonable speed, etc. have put it in I hear over 400,000 installations (said so in some magazine in an article about OTHER networks!) I know of users in the * Business industry (Datapoint customers like the local city government with all departments on an ARCnet of many nodes.) * factory floor (large German manufacturer) * Actually anywhere you see nets, you'll see ARCnet. Remember, It was one of the first high speed commercial PC machine nets. And is still up there performance-wise against all newcommers in this market. (OK, not 50MegaBaud Hyperchannel but we're talking PCs here!) >What are the achievable data rates? Ask anyone about effective rates and you get down to issues of OS performance as well (how well/much can the OS handle). But let me mention some interesting facts even if not quite what you requested. * The system is defined as 2.5MBaud but because it uses an isocronous(sp?) transmission scheme (resync on each character in a message) to send 8 data bits you must send 11 baud (3 sync bits preceed each data bit) therefore the effective data rate is about 1.8MegaBit per second. * When one person was testing some (bad?) hardware on a live network while many REAL users were using it, the response time degraded. The network of course still operated correctly but was loaded down by over 400 (256 byte) messages per second. * A live ARC system (at Datapoint again) had over 200 nodes on it (max is 255). About 150+ were active on the net and the message rate was about 200 per second. (And yes, I saw this myself.) Response time was good enough that all engineering nodes in R&D were diskless (not even diskettes). And, many/most other nodes were diskless too. Dedicated files servers were used but the OS, a newer one written in '80 called RMS, considered any node a requestor or server so you could go to the Server and use it like any other machine. They were just used as Servers so that all of memory could be a disk cache (fully dynamic, run an App. and cache shrinks). Response time? OK, not as good as a local disk but good enough that it was not an issue. In fact, in one test a copy from file server to file server by a user machine was slightly faster than a local copy! Why? the caching! The file server could pre-read and post-write whole tracks to/from the disk optimally servicing requests from the network. Meanwhile the programme in the local machine was being handed BIG buffers of data that it just "wrote" back out over the net back to a file server. >Where can I get literature on arcnet? Try: Standard Micro Systems (they make the chip and sell a PC board) Datapoint (of course) (They may have an 800 number) Radio Shack (UGH!) Does sell some ARC hardware. Novell puts its LAN on ARCnet (and one of the fastest implementations) >Yakim Martillo Shalom v'litraot Yakim -- UUCP:...!amdahl!drivax!socha WAT Iron'75 "Everything should be made as simple as possible but not simpler." A. Einstein
socha@drivax.UUCP (Henri J. Socha (7-x6628)) (11/25/87)
OOPS, I made a typo in the previous message (and an important one) please 'n' if you 'n'd the ARCnet discussion. In article <2756@drivax.UUCP> socha@drivax.UUCP (Henri J. Socha (7-x6628)) writes: > I know of users in the > * Business industry (Datapoint customers like the local city government with > all departments on an ARCnet of many nodes.) **** That was: The local city govt. uses a Datapoint ARCnet system and they are very happy with it (including the programmers) last time I talked with them. > * The system is defined as 2.5MBaud but because it uses an isocronous(sp?) > transmission scheme (resync on each character in a message) to send > 8 data bits you must send 11 baud (3 sync bits preceed each data bit) **** OOPS that's 3 re-sync bits per BYTE! > therefore the effective data rate is about 1.8MegaBit per second. (2.5 * 8/11) -- UUCP:...!amdahl!drivax!socha WAT Iron'75 "Everything should be made as simple as possible but not simpler." A. Einstein