Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: SCSI II specs Message-ID: <14620@cbmvax.commodore.com> Date: 24 Sep 90 17:47:17 GMT References: <1232@tardis.Tymnet.COM> <3769@ruuinf.cs.ruu.nl> <14418@cbmvax.commodore.com> <1990Sep20.125810@wjg.enet.dec.com> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 34 In article wayned@wddami.spoami.com (Wayne Diener) writes: >>In article <1990Sep20.125810@wjg.enet.dec.com> guineau@wjg.enet.dec.com (W. John Guineau) writes: >>SCSI II also specifies a 32 bit data path option. Couple that with FAST >>and you get 40MB/s. Both 16 and 32 bit require a second cable (termed the >Before everyone gets too excited about the _possible_ data transfer rates >for high speed disk drives, just remember that you _cannot_ take the data >off the disk & put it somewhere useful (i.e. memory) at any higher rate >than the bandwidth of the bus. I don't know what the bandwidths of the >Zorro I/II/III busses are, but I have serious doubts that a 40 MB (or even >20 MB) per second transfer rate is possible. Zorro III can handle 20 MB/s on-bus with no problems, though not going to the A3000's 68030 bus fast memory. And between a Zorro III master and slave with burst capability, 40 MB/s is certainly possible. Which doesn't matter in this case, because the A3000's DMA controller is not on the Zorro III bus, it's on the 68030 bus. That bus would have no trouble supporting 40 MB/s transfers, though the standard A3000 memory isn't quite that fast. Which doesn't matter in this case, because the A3000's SCSI chip is only an 8 bit SCSI, which, even with the fastest SCSI-2 transfer, only yields 10 MB/s. So you're not likely to have much trouble with the A3000's internal bus speeds. Anyone planning a 32 bit SCSI-2 bus mastering Zorro III board, feel free to give me a call. I'll help you all you need if I get free sample :-)... >| // Wayne D. Diener | -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Standing on the shoulders of giants leaves me cold -REM