admiral%m-5@Sun.COM (Michael Limprecht SUN Microsystems Mt. View Ca.) (10/04/89)
Does anyone out there know of any boards for the A2000 that's a bus master? I'm doing some research on the amiga 2000 bus. Please email me with the responses. Thanks in advance. Mick sun.com!admiral
swarren@eugene.uucp (Steve Warren) (10/04/89)
In article <125730@sun.Eng.Sun.COM> admiral%m-5@Sun.COM (Michael Limprecht SUN Microsystems Mt. View Ca.) writes: > >Does anyone out there know of any boards for the A2000 that's a >bus master? > >I'm doing some research on the amiga 2000 bus. > >Please email me with the responses. > >Thanks in advance. > >Mick >sun.com!admiral Which brings up a point, and I would appreciate it if someone really knowledgeable about the Amiga bus would answer. I keep seeing articles about IBM's MC bus standard, and as I read them I keep trying to find what it is about MC that is so special. I recently saw an article which promoted an 80 MB/s bus speed on 32-bit MC busses, which I didn't credit (it was some kind of marketing announcement, and I don't think they had the hardware to demonstrate these speeds). Can someone please explain what it is conceptually about MC bus architecture that is so unique, and in what ways this is superior to the Amiga bus (besides sheer speed). It looked to me like they were getting excited because it allowed auto-config. --Steve ------------------------------------------------------------------------- {uunet,sun}!convex!swarren; swarren@convex.COM
daveh@cbmvax.UUCP (Dave Haynie) (10/05/89)
in article <1956@convex.UUCP>, swarren@eugene.uucp (Steve Warren) says: > Keywords: bus master A2000 boards > Which brings up a point, and I would appreciate it if someone really > knowledgeable about the Amiga bus would answer. I keep seeing > articles about IBM's MC bus standard, and as I read them I keep > trying to find what it is about MC that is so special. I think lots of people are trying to figure out the same thing. Which basically points to the truth -- there's nothing all that special about the new IBM Microchannel bus. It's a basic 32 bit, non-multiplexed bus with fairly arbitrated multimaster capability and a pseudo-autoconfiguration mechanism. All the hum about it was generated, I suspect, for two reasons. First of all, because it has the IBM name on it, which some folks respect for some reason (I guess before my time -- I've only been active in the computer business for about 10 years). And, if nothing else, IBM is BIG, so anything they do is bound to have an effect, even if it's a negative effect. Secondly, because of how bad the IBM XT/AT buses are. For instance, the XT/AT buses don't allow interrupts to be shared, so if one card uses a particular interrupt line, no other card can. Soon you run out of interrupts. Also, there's no way for an expansion card to master the bus, and the DMA controller in these systems (which, in an ideal world, could run transfers at 1/2 the rate of a bus master for things like hard disk transfers, etc) is so slow, most folks opt for using programmed I/O (eg, the CPU does the transfers) anyway. And of course, XT/AT cards are simply I/O and memory mapped at fixed locations, so when you add one, you typically have to adjust jumpers so that your new board doesn't conflict with any of the older boards. All of these issues were addressed in the Amiga Bus originally, so other than for speed and arbitration fairness, the Microchannel bus doesn't sound all that amazing compared to the Amiga bus. Or the NuBus in the Mac II. In fact, while I haven't actually used a Microchannel system, the stories I've heard about it make it's autoconfiguration mechanism (or perhaps just the OS/2 interface to this mechanism) real bad compared to what you have in the Amiga system. For instance, when you plug a memory card in the Amiga bus, it gets added into the memory pool on the next powerup, automatically. If you remove it, it goes away. If you add a hardware device, like this Bridge Card I have here, it's device driver gets automatically bound in on startup (assuming you copied the driver into SYS:Expansion on your boot disk), when you remove the card, the driver doesn't get started. Apparently, on the Microchannel, you have to specifically tell the system to add a card in. And when you remove a card, you have to specifically tell the system it's leaving, or it won't boot. Like I said, I haven't tried it, but one of the folks discussing this on BIX said that you've basically "traded hardware jumpers for software jumpers". Amigas generally work without any jumpers, and I gather Mac IIs work about as well. So it's obvious that IBM doesn't have all the answers. > I recently saw an article which promoted an 80 MB/s bus speed on 32-bit MC > busses, which I didn't credit (it was some kind of marketing announcement, > and I don't think they had the hardware to demonstrate these speeds). You have to watch bus speed claims, because a maximum rate rarely tells you the whole story. For instance, the Mac NuBus has a top speed around 32 MB/s (as I recall), but the CPU access is closer to 3.5 MB/s. Top speed is only in burst mode, which typically can only be achieved between I/O devices. So take the base maximum stated speed of MC bus, which is 20 MB/s (I don't know what mode; chances are the CPU isn't talking this fast on the bus). Now double the mimimum bus cycle time; now you're at 40MB/s. Now, instead of sending address on 32 wires and data on another 32, send address out on 32 wires, let whoever's listening latch that address, and then send data out on 64 wires. Now you're up to 80MB/s. That's essentially, if not exactly, what IBM's doing here. Depending on how clever they were when they designed the bus, existing implementations may or may not be able to support these new modes. Certainly existing implementations won't all of a sudden start sending 64 bit data packets, but they may work OK with bus master and slave cards that want to talk that way between each other. Some company's recently discussed a very similar 64 bit approach on VME bus, and you can certainly imagine that the same principles can be applied to any bus that's sophisticated enough to keep the "old-mode" cards at least quiet while any "new-mode" things are on the bus. > It looked to me like they were getting excited because it allowed > auto-config. To a large extent, they were -- that's what most of the world sees in the new IBM bus. Then again, to a part of the computer world, IBM is computers, and if they don't have it, it doesn't exist. In fact, you can often understand a conversation between IBMers if you substitute the phrase "has finally adpoted" for the word "invented". As in, "IBM invented the 3.5 inch microfloppy drive", "IBM invented an autoconfiguring expansion bus", etc. > --Steve -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Too much of everything is just enough
brian@grebyn.com (Brian Bishop) (10/08/89)
In article <8103@cbmvax.UUCP> daveh@cbmvax.UUCP (Dave Haynie) writes: [ lots of stuff about how IBM's new bus is no big deal ... then: ] >and if they don't have it, it doesn't exist. In fact, you can often >understand a conversation between IBMers if you substitute the phrase >"has finally adpoted" for the word "invented". As in, "IBM invented the >3.5 inch microfloppy drive", "IBM invented an autoconfiguring expansion bus", >etc. Ahhh!!!! Yes, this sums up the nasty feeling I have about 'BM entirely. You see, I have this nightmare that I am a 40 year-old hacker somwhere (I'm 24 now) and someone offhandedly mentions that IBM invented multitasking when they released OS/2. Aiiieeeeeeeeeeeee!!!! Brian "Caught With His .Sig Down" Bishop
phil@ingr.com (Phil Johnson) (10/13/89)
In article <13998@grebyn.com> brian@grebyn.UUCP (Brian Bishop) writes: > Ahhh!!!! Yes, this sums up the nasty feeling I have about 'BM >entirely. You see, I have this nightmare that I am a 40 year-old >hacker somwhere (I'm 24 now) and someone offhandedly mentions that IBM >invented multitasking when they released OS/2. Aiiieeeeeeeeeeeee!!!! I BEG your pardon, forty is fine 8-{). You can bet IBM will announce their discovery of a new approach to computing. They will dub it multitasking and the official name will be OS/2. They did this with 5 1/4 inch floppies about 7 or eight years ago and have mentioned a new more portable media in a smaller size in the past 2 years. I can hardly wait for this new inovation maybe they have developed a disk that will fit in a shirt pocket. WOW! -- Philip E. Johnson UUCP: usenet!ingr!b3!sys_7a!phil MY words, VOICE: (205) 772-2497 MY opinion!
pa1014@sdcc13.ucsd.EDU (pa1014) (10/13/89)
I believe it was IBM that invented the original floppy disk, so maybe
their claims concerning floppies are valid (maybe not the pocket
sized, though). Let them claim what they want, we know better and
if those CBM commercials are any good...
Vinh Le
BitNet: vle@UCSD.BITNET
InterNet: vle@UCSD.EDUjoe@cbmvax.UUCP (Joe O'Hara - QA) (10/13/89)
In article <6862@ingr.com> phil@ingr.UUCP (Phil Johnson) writes: >In article <13998@grebyn.com> brian@grebyn.UUCP (Brian Bishop) writes: > >> Ahhh!!!! Yes, this sums up the nasty feeling I have about 'BM >>entirely. You see, I have this nightmare that I am a 40 year-old >>hacker somwhere (I'm 24 now) and someone offhandedly mentions that IBM >>invented multitasking when they released OS/2. Aiiieeeeeeeeeeeee!!!! > >I BEG your pardon, forty is fine 8-{). ^^^^^^^^^^^^^ | | I wholeheartedly agree! :-) > >You can bet IBM will announce their discovery of a new approach to computing. >They will dub it multitasking and the official name will be OS/2. IBM did pretty much the same thing in the mainframe world. Honeywell and Burroughs had multi-tasking/multi-processing machines circa 1960. Yet IBM 'discovered' multi-tasking with the release of System/370. Go figure. > >They did this with 5 1/4 inch floppies about 7 or eight years ago and have >mentioned a new more portable media in a smaller size in the past 2 years. > >I can hardly wait for this new inovation maybe they have developed a disk that >will fit in a shirt pocket. WOW!
bn@attcc.UUCP (10/17/89)
/* Written 10:15 pm Oct 12, 1989 by pa1014@sdcc13.ucsd.EDU in attcc.UUCP:comp.s.amiga */ I believe it was IBM that invented the original floppy disk, so maybe their claims concerning floppies are valid Actually, it was some guy in Japan. He also invented some sort of chair which gives you the equivalent of 8 hours of sleep in just 1 hour. (sounds just like just what I need)