garys@techbook.com (Gary Scott) (04/12/91)
OK all you PC Hardware People Here is a question that I have been trying to get a reasonable answer to for several weeks without any solid response. Situation: I intend to purchase a new hard drive and controller for use on a 486/33 Question: How do I determine what drive/controller will give me maximum performance for minimum $$$$. Just buying the most expensive drive/contoler combo may not be the optimum solution. My computer has a standard AT bus, so at some point the bus speed becomes the limiting factor along with the controller card. High transfer rate specs for drives only covers the exchange between the drive and controller and is not the (w)hole picture as the bus and processor cannot run at drive transfer speed. Ideally, I would want to purchase a controller and drive combo that would exceed the bus throughput rate by say 10%. Qusetion: How do I determine what the maximum bus throughput rate is for an AT bus? How do I measure the throughput rate? What is the optimum controller/drive combo? My current research says that I should go with an EDSI drive with about a 20MB transfer rate and the cheap Ultrastore controler that has a 32K cache. I can't find any reason to use the multi-meg cache controllers as the system will be running single user DOS/Windows. Any thoughts/experiences/help would be greatly appreciated. Thanks. Gary Scott -- Gary L. Scott, Decision Technology, Beaverton, OR (503) 642-4196 "Strategic Business Applications" garys@techbook.com (subscription unix) Any opinion expressed are mine and do not reflect the opinion of anyone including myself!!!
douglass@davidsys.com (JEFF (PC) DOUGLASS) (04/24/91)
In article <1991Apr12.043027.2695@techbook.com>, garys@techbook.com (Gary Scott) writes: > > I intend to purchase a new hard drive and controller for use on a 486/33 >[ ... ] > solution. My computer has a standard AT bus, so at some point the bus speed > becomes the limiting factor along with the controller card. High transfer > rate specs for drives only covers the exchange between the drive and > controller and is not the (w)hole picture as the bus and processor cannot > run at drive transfer speed. A 33.3 MHz 80386 with an 8.33 MHz AT bus can handle about 3 MB/s. (At least that's what I get. On an 8 MHz 80286 I get 2+ MB/s.) This is flat out, assuming that the device on the bus supports 0 ws. Faster on certain machines under certain conditions. Most hard drives spin at 3600 RPM. That's 60 RPS(revs per second). All current (PC) hard drives only read one head at a time. (Too bad) Many hard drives have 36 or fewer 512 byte sectors per track. Taking all these together, I get: 60*36*512 = 1,105,920 or about 1 MB/sec. drive transfer rate. Yes, there are some drives with >36 sectors/track. I have heard rumors about future drives that will spin faster than 3600 RPM, and have 64+ sectors per track. Sector size would probably still be 512 bytes. Consider 5400 RPM, 64 sectors at 512 bytes is close to 3 MB/s. Not bad, but the bus can still probably keep up with it. Best would be a hard drive that reads/caches all heads. In that case, 60*36*(15 heads)*512 = about 15 MegaBytes per second! > Ideally, I would want to purchase a controller and drive combo that would > exceed the bus throughput rate by say 10%. You shouldn't want a controller that exceeds the speed of the bus by anything. > My current research says that I should go with an EDSI drive with about a > 20MB transfer rate and the cheap Ultrastore controler that has a 32K cache. > I can't find any reason to use the multi-meg cache controllers as the system > will be running single user DOS/Windows. Some ESDI-buses are 15 Mb/s (that's 15 Mega-bit/second) = under 2 MB/s if you can find a drive to keep up. Any 20 MB/s (read MegaByte/sec) drive of ANY kind I WANT to know about! No, I'm not interested in a floor-mount model :-) > Any thoughts/experiences/help would be greatly appreciated. Thanks. > Gary Scott > -- > Gary L. Scott, Decision Technology, Beaverton, OR (503) 642-4196 > "Strategic Business Applications" garys@techbook.com (subscription unix) > Any opinion expressed are mine and do not reflect the opinion of anyone > including myself!!! [personal opinion mode on] ST-506 I've had these up to 500+ KB/s, 1:1 interleave 17 sector drive. SCSI I've gotten over 1 MB/s with a small drive of _only_ 300 MB (36 sec). The larger drives (1 GB) ARE quicker. ESDI I've tried the older 10 Mb/s ESDI-bus. Drive had ?? sec, I saw 1 MB/s. IDE Actually a variant of ST-506 with embedded controller on the drive. My current drive has 32 sectors/track. I get 880+ KB/s uncached. Of course this doesn't even consider that there could be a cache on the drive itself. Since the bus is slower than main RAM by a factor of up to (fill in this blank), I kinda prefer local write-through cacheing (in CPU space) using any/all 'unneeded' ram (up to 15 MB?). [personal opinion mode off] -- -{JD}- Jeff (Douglass@DavidSys.Com) David Systems, Sunnyvale CA,(408)720-8000 "Never count on the inevitable until it happens. . ."