gerry@zds-ux.UUCP (Gerry Gleason) (01/11/90)
In article <47800@sgi.sgi.com> rpw3@rigden.UUCP (Robert P. Warnock) writes: >X3T9.3 is also looking at a Fiber Channel (FC) version of HPPI. At least two >companies offer single chips *today* which take HPPI-speed 32-bit-word streams >and serialize them into gigabit/sec bit-serial streams, and vice-versa. The >holdup right now is affordable fiber-optoelectronics at gigabit speeds, but >that will change. And in the mean time, people are considering going back >to *copper* (but still bit-serial to keep the cables small) for "I/O bus" >distances, since wire is still cheap. [Yes, you can run at 1 Gb/s over cheap >coax, for some 10's of meters. That's about the same distance as HPPI-PH.] That reminds me, I've been thinking about the possibility of fiber as a replacement for SCSI and/or present LAN technologies. The application would be more typical desktop micro's, not killer micro's so the bandwidth doesn't need to be pushing the limits, and cost is a much more important factor. To be practical, the implementation would be constrained as follows: 1) Bandwidth appropriate to cheap optoelectronics and serial to parallel conversion. Preferably a single chip that can directly drive an infra-red LED. 2) Bandwidth fast enough to beat (or at least tie) what it replaces (SCSI = 1-40MB/s =~10-300M bits/s >> Ethernet). 3) Cheap, simple connectors and cables. I recently read about plastic fibers, which are thicker so they capture light from higher angles, which should also imply that the connectors don't need to be a precisely made (any comments on this?). So, is this reasonable? What are the limits of "cheap" opto-electronics (for me, cheap is < 10$ for a transmitter and reciever, with an expectation that it could be 1/10 that for large quantities in a year or two). If it's cheap enough it could be applied to interconnecting digital audio and video components too. Gerry Gleason
rpw3@rigden.wpd.sgi.com (Robert P. Warnock) (01/11/90)
In article <94@zds-ux.UUCP> gerry@zds-ux.UUCP (Gerry Gleason) writes: +--------------- | That reminds me, I've been thinking about the possibility of fiber as a | replacement for SCSI and/or present LAN technologies. The application | would be more typical desktop micro's, not killer micro's so the bandwidth | doesn't need to be pushing the limits, and cost is a much more important... | 2) Bandwidth fast enough to beat (or at least tie) what it | replaces (SCSI = 1-40MB/s =~10-300M bits/s >> Ethernet). | So, is this reasonable? What are the limits of "cheap" opto-electronics | (for me, cheap is < 10$ for a transmitter and reciever... +--------------- Well, plastic fibers (e.g. H-P 1mm plastic "snap-in" links) can be made to run at Ethernet speeds at distances to 25 meters; I've done it. (Yes, they're only rated for 5 Mbaud, but if you use "impulse coding" you can get 10 Mbit/sec easily and *very* reliably. And impulse coding can be converted/deconverted to Manchester, so you can use standard Ethernet chips.) And an active multi-port star coupler is very simple, and needs no clocks, due to the impulse coding. But much above Ethernet speeds, the pulse dispersion in the fiber kills you. 1mm fiber has a numerical aperture of about 0.6, which limits the distance to not much more than a bit-time's "length". For example, 10 Mb/s -> 100ns -> ~20 meters. It's better than that (obviously, see above), but not much. And unfortunately, the cost of a pair of transmitter/receivers plus several meters of plastic is not much cheaper than today's Ethernet transceiver chips plus some RG-58C/U. It's a technology whose time passed it by. (*sigh*) (...unless you *have* to have very high isolation.) In any case, glass fibers aren't that expensive anymore, and plastic- packaged optics for glass have appeared which will handle plain 20Mbaud data (and therefore 10 Mb/s Manchester), so at 10Mb/s I'd just use some kind of fiber-"Ethernet"-with-active-hub. Rumor has it that the standards folk will look at 10baseF right after 10baseT gets steadied down. The next convenient speed above that is 100 Mb/s, which you can get up to several hundred meters with relatively cheap glass or PCS fiber, plastic package 900nm optics, and AMD "TAXI" serializers. Cost per end of a full duplex "fiber UART" (optics + TAXIs) is less than $100, and likely to fall. This is FDDI speed (uses FDDI's 4b/5b coding), but *much* cheaper. With a simple "byte bridge" active hub, you could use it like a 100Mb/s "Ethernet". The hub would cost just a few bucks + <$100 per port... about the same or less than a 10baseT hub. I've nicknamed it "100baseF", but I doubt it will really get standardized any time soon... ;-} (FDDI is too "hot" right now.) And then there are the gigabit speed devices I mentioned in the previous article. "1000baseF"??? Well, for now gigabit/sec optics are *very* expensive (need lasers?), but cheap coax works for ~30 meters if you can accept wire. So that's the range of links I know of. For the "fiber-as-I/O-bus" I'd probably choose the 100Mb/s speed, since it could handle even fast SCSI. (Note that it's also roughly the same speed as a fast IBM 370 I/O channel.) For performance, you'd need a link per device; for cost, you'd share a "channel" among several devices with a hub. -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
ching@snap.amd.com (Mike Ching) (01/12/90)
In article <94@zds-ux.UUCP> gerry@zds-ux.UUCP (Gerry Gleason) writes:
-
-That reminds me, I've been thinking about the possibility of fiber as a
-replacement for SCSI and/or present LAN technologies. The application
-would be more typical desktop micro's, not killer micro's so the bandwidth
-doesn't need to be pushing the limits, and cost is a much more important
-factor. To be practical, the implementation would be constrained as
-follows:
-
- 1) Bandwidth appropriate to cheap optoelectronics and serial
- to parallel conversion. Preferably a single chip that
- can directly drive an infra-red LED.
- 2) Bandwidth fast enough to beat (or at least tie) what it
- replaces (SCSI = 1-40MB/s =~10-300M bits/s >> Ethernet).
- 3) Cheap, simple connectors and cables. I recently read
- about plastic fibers, which are thicker so they capture
- light from higher angles, which should also imply that
- the connectors don't need to be a precisely made (any
- comments on this?).
-
-So, is this reasonable? What are the limits of "cheap" opto-electronics
-(for me, cheap is < 10$ for a transmitter and reciever, with an expectation
-that it could be 1/10 that for large quantities in a year or two). If it's
-cheap enough it could be applied to interconnecting digital audio and video
-components too.
-
-Gerry Gleason
At AMD we have toyed with the idea of building a SCSI cable using our TAXI
transceivers (32-140Mbit serial data rate) and fiber. We estimated that the
cable would probably cost $75. I suppose a large market would drive the cost
down.
Mike Chingemv@math.lsa.umich.edu (Edward Vielmetti) (01/13/90)
In article <28758@amdcad.AMD.COM> ching@snap.amd.com (Mike Ching) writes:
At AMD we have toyed with the idea of building a SCSI cable using our TAXI
transceivers (32-140Mbit serial data rate) and fiber. We estimated that the
cable would probably cost $75. I suppose a large market would drive the cost
down.
Mike, SCSI cables (q1) are already in the $75 range if they're relatively
scarce and hard to make yourself (i.e. sparcstation cables). You'd
have no problem with the cost. Now how far would you be able to
get the drive away from the workstation?
--Ed
ps. anyone for comp.periphs.scsi? discussion now in comp.periphs.gideony@microsoft.UUCP (Gideon YUVAL) (01/14/90)
In article <28758@amdcad.AMD.COM> ching@snap.AMD.COM (Mike Ching) writes: >At AMD we have toyed with the idea of building a SCSI cable using our TAXI >transceivers (32-140Mbit serial data rate) and fiber. We estimated that the >cable would probably cost $75. I suppose a large market would drive the cost >down. > What do ordinary SCSI cables cost (to compare to that $75 figure)? Is there also a cost per extra foot of cable? Thanks -- Gideon Yuval, gideony@microsof.UUCP, 206-882-8080 (fax:206-883-8101;TWX:160520)
ching@pepsi.amd.com (Mike Ching) (01/15/90)
In article <EMV.90Jan12140628@urania.math.lsa.umich.edu> emv@math.lsa.umich.edu (Edward Vielmetti) writes: -In article <28758@amdcad.AMD.COM> ching@snap.amd.com (Mike Ching) writes: - - At AMD we have toyed with the idea of building a SCSI cable using our TAXI - transceivers (32-140Mbit serial data rate) and fiber. We estimated that the - cable would probably cost $75. I suppose a large market would drive the cost - down. - -Mike, SCSI cables (q1) are already in the $75 range if they're relatively -scarce and hard to make yourself (i.e. sparcstation cables). You'd -have no problem with the cost. Now how far would you be able to -get the drive away from the workstation? I was a bit careless. The $75 is component cost. Retail would be 2-3x that? You could send data over 2 kilometers using fiber. Using copper would make the component cost $40 and the distance 30-100 meters depending on the quality of the coax. Anyway we decided that the low demand for differential SCSI meant it wouldn't have wide appeal either. (BTW, we weren't trying to build these. Just considering it for an application note for the chips. Our business is ICs.) Mike Ching
gnb@bby.oz.au (Gregory N. Bond) (01/16/90)
In article <28795@amdcad.AMD.COM> ching@pepsi.amd.com (Mike Ching) writes:
You could send data over 2 kilometers using fiber. Using copper would make
the component cost $40 and the distance 30-100 meters depending on the
quality of the coax. Anyway we decided that the low demand for differential
SCSI meant it wouldn't have wide appeal either. (BTW, we weren't trying
to build these. Just considering it for an application note for the chips.
Our business is ICs.)
Wow. I reckon there would be a market for this. How often have I
cursed having to walk down 3 flights of stairs to get to the machine
room to change a cartridge tape? When the tapes live in the storeroom
on my floor? Run a fibre scsi bus to an unused corner of my office,
stick the tape drive there, and no more walking, and no dumping across
the ethernet!
Where do I order?
Greg.
--
Gregory Bond, Burdett Buckeridge & Young Ltd, Melbourne, Australia
Internet: gnb@melba.bby.oz.au non-MX: gnb%melba.bby.oz@uunet.uu.net
Uucp: {uunet,pyramid,ubc-cs,ukc,mcvax,prlb2,nttlab...}!munnari!melba.bby.oz!gnbgerry@zds-ux.UUCP (Gerry Gleason) (01/17/90)
In article <28795@amdcad.AMD.COM> ching@pepsi.AMD.COM (Mike Ching) writes: >-In article <28758@amdcad.AMD.COM> ching@snap.amd.com (Mike Ching) writes: >- At AMD we have toyed with the idea of building a SCSI cable using our TAXI >- transceivers (32-140Mbit serial data rate) and fiber. <I was a bit careless. The $75 is component cost. Retail would be 2-3x that? <You could send data over 2 kilometers using fiber. Using copper would make <the component cost $40 and the distance 30-100 meters depending on the <quality of the coax. Anyway we decided that the low demand for differential <SCSI meant it wouldn't have wide appeal either. (BTW, we weren't trying <to build these. Just considering it for an application note for the chips. <Our business is ICs.) Let's be clear about this. I assume you are talking about an assembly with SCSI connectors on both ends, and modules that convert to and from the fiber. In this case wouldn't the costs be much more equivalent since the transceivers and conversion electronics more or less replace the SCSI interface circuitry? Of course SCSI drives are available from many people now, and to do what I'm suggesting means you'd have to almost make your own drive controllers, but why worry about such details ;-). Gerry Gleason
brb@rhi.hi.is (Bjorn R. Bjornsson) (01/17/90)
In article <28758@amdcad.AMD.COM> ching@snap.amd.com (Mike Ching) writes: >At AMD we have toyed with the idea of building a SCSI cable using our TAXI >transceivers (32-140Mbit serial data rate) and fiber... and In article <28795@amdcad.AMD.COM>, ching@pepsi.amd.com (Mike Ching) writes: >... Just considering it for an application note for the chips. > Our business is ICs.) I saw a new product brief for an SCSI fiber optic extender about a year ago. Needless to say, I no longer remember who makes these, but I seem to recall a max distance of a about 1 km. I can certainly think of situations where such a cable could come in handy, especially if the transceivers aren't too bulky and don't need a lot of power. -- Bjorn R. Bjornsson brb@falcon.is Gagntaekni / Bijective Tech.