Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!sjsca4!poffen From: poffen@sj.ate.slb.com (Russ Poffenberger) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: ISA SCSI adapters - summary of replies Keywords: ISA, SCSI, adapter Message-ID: <1990Jul26.204317.6899@sj.ate.slb.com> Date: 26 Jul 90 20:43:17 GMT References: <2683@bruce.cs.monash.OZ.AU> <8527@inco.UUCP> Reply-To: poffen@sj.ate.slb.com (Russ Poffenberger) Distribution: comp Organization: Schlumberger Technologies, San Jose, CA. Lines: 39 In article <8527@inco.UUCP> pauls@inco.UUCP (Paul Stygar) writes: >In article <2683@bruce.cs.monash.OZ.AU> herbie@bruce.cs.monash.OZ.AU (Andrew Herbert) writes: >>Here is a summary of the information I received regarding AT bus scsi cards. >>Many thanks to the people that replied. > ... >>I have not included prices > > Best price I've seen on the 1542B is at Treasure Chest > (see ad in Computer Shopper for phone #) ... about $230 > >>Adaptec AHA1540B/1542B >>---------------------- >>* Maximum SCSI->AT transfer rate: 10M bytes/s (motherboard-dependent). >> (Bus master DMA, => card drives bus directly, not via the PC's DMA >> controller.) > > Where did this info come from ???? > I didn't see any info in the User Manual for the 1542B > to directly confirm this ... > > The board can be jumpered to set the DMA Transfer Speed > to 5.0, 5.7, 6.7, or 8.0 MB/s (via PINS 12,13 of the J5 Jumper Block) > (p. 2-9 of AHA-1540B/1542B User's Manual, Rev 1.0, April 1990). > > Not to mention, I don't understand this info, since the 1542B > seems to run OK on an ancient (circa 1988) MICRONICS 20 Mhz > motherboard which only supports 4 Mhz DMA transfer rate. Most likely the reason why it works is because the disk itself is the limiting factor. I have only been able to achieve an actual transfer rate of 3Mbytes/sec from a disk that has a lot of cache on it, and even then, this is really only a real benefit under very limited circumstances. (Where you happen to be reading the same disk data over and over, like some disk benchmark programs.) Russ Poffenberger DOMAIN: poffen@sj.ate.slb.com Schlumberger Technologies UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen 1601 Technology Drive CIS: 72401,276 San Jose, Ca. 95110 (408)437-5254