acs@pccuts.pcc.amdahl.com (Tony Sumrall) (12/22/88)
Has anyone hooked up an ESDI drive to an Amiga? I've seen some prices here in Sillycon Valley that are quite competitive with SCSI. Having also seen Adaptec SCSI->ESDI controllers available for around $100 it seems like it may be a worthwhile (read "about as cheap...or expensive") move. Since I know nothing about ESDI, I have no idea if a run-of-the-mill SCSI driver will work in this config nor if it's even a good idea. Are ESDI drives more reliable? Will I lose anything by going ESDI instead of SCSI? Does ESDI provide anything (aside from, perhaps, an increase in transfer speed) that SCSI doesn't? Reply to me and I'll summarize. -- Tony Sumrall acs@pccuts.pcc.amdahl.com <=> amdahl!pccuts!acs [ Opinions expressed herein are the author's and should not be construed to reflect the views of Amdahl Corp. ]
thad@cup.portal.com (Thad P Floryan) (12/25/88)
Re: Tony Sumrall's question "Has anyone hooked up an ESDI drive to the Amiga?" the answer is yes. Several callers to BBS-JC (415/961-7250) have done so using an Adaptec translator (ESDI<=>SCSI). Feel welcome to call BBS-JC and browse the archives for more specifics (i.e. Adaptec part number, disk drives that have been known to function, etc.) If "raw" performance is your quest, the advantage of such drives is minimal. Even though (for example) the Maxtor XT-4380 is less expensive than its SCSI counterpart (the XT-3380), any purported benefits of ESDI are negated by the need to translate to/from SCSI. Even a "straight" ESDI connection (as reported in various UNIX REVIEW test reports over the past 6 months) appears to be slower than what one can expect using SCSI on the Amiga under 1.3 with the FFS. PLEASE NOTE: those reported speed differences are most likely due to the OS and file system and not because of intrinsic speed differences of the actual hardware interface. Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]
lphillips@lpami.wimsey.bc.ca (Larry Phillips) (12/26/88)
In <12915@cup.portal.com>, thad@cup.portal.com (Thad P Floryan) writes: > If "raw" performance is your quest, the advantage of such drives is minimal. > Even though (for example) the Maxtor XT-4380 is less expensive than its SCSI > counterpart (the XT-3380), any purported benefits of ESDI are negated by the > need to translate to/from SCSI. This is like saying that any purported benefits from ST506 are negated by the need to translate to/from SCSI, as is done with any SCSI controller (as opposed to an SCSI host adapter). ESDI is a controller/drive interface spec, as are ST506 or ST412. More than likely, the lack of expected performance improvement is due to another factor. I would suspect the Adaptec cotroller, judging from their rather poor performance in the SCSI/St506 area. -larry -- "Intelligent CPU? I thought you said Intel CPU!" -Anonymous IBM designer- +----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca or uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 | +----------------------------------------------------------------------+
thad@cup.portal.com (Thad P Floryan) (12/28/88)
Re: Larry Phillips' comments to my answer to Tony Sumrall's question about ESDI on the Amiga ... It's clear (now) that my answer wasn't clear. (Howzat? :-) ST506/ST412 is "ancient". That interface was in its heyday during the early years of the IBM/PC. Surprisingly, I get over 250KBytes/second from a Maxtor XT-2190 connected to an Adaptec 4000A SCSI<=>ST506/ST412 on the Amiga using 1.3 with FFS (and the Supra 4x4 interface). This performance exceeds that published for most of the "modern" systems that are reviewed in, for example, UNIX REVIEW (ref. Compaq 386, PS/2-80, certain Sun-3, etc.) ESDI is a modern, high speed interface, as is SCSI. "RAW" speed of both a modern SCSI and an ESDI interface "should be" around 750KBytes/second, but this is not achieved in practice (likely due to an OS and its filesystem) One caller to BBS-JC (Steven Schaem) claims DiskPerf results of over 350KBytes per second with his ESDI drive and an Adaptec SCSI:ESDI translator on his Amiga; you'd have to ask him for more details since I'm not in the habit of "capturing" the message base (40-100 messages/day) on BBS-JC. The point I wanted to make is that any cost savings (of an ESDI) drive would be negated simply by the need to purchase a translator (such as Adaptec's) and that one would not see any performance gains; the embedded SCSI drives themselves are extremely fast. Thus, the $200 saved (getting, for example, a Maxtor XT-4380 ESDI drive instead of the XT-3380 SCSI drive) are "lost" by the need to get a SCSI translator with attendant power cabling, ESDI cabling and connectors, etc. (plus having one more "box" in the chain (the translator) as a source of potential problems (interface, reliability, whatever...)). Getting a translator for a high-performance (and LOW cost) ST506/412 drive does make economic sense, and there's no apparent performance penalty. Most of the people I know who've added ESDI drives to their Amigas have done so solely because either "the drives were available at work" or "I got the drive on an indefinite loan." For THOSE people, it did make economic sense to use the ESDI drive. To date, I'm not aware of anyone making a "native" ESDI interface for the Amiga and, due to SCSI's other advantages, I don't foresee anyone doing so on a commercial basis (making an ESDI interface,that is) Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]
lphillips@lpami.wimsey.bc.ca (Larry Phillips) (01/01/89)
In <12995@cup.portal.com>, thad@cup.portal.com (Thad P Floryan) writes: > Re: Larry Phillips' comments to my answer to Tony Sumrall's question about > ESDI on the Amiga ... >Surprisingly, I get over 250KBytes/second from a Maxtor XT-2190 connected to >an Adaptec 4000A SCSI<=>ST506/ST412 on the Amiga using 1.3 with FFS (and the >Supra 4x4 interface). This performance exceeds that published for most of >the "modern" systems that are reviewed in, for example, UNIX REVIEW (ref. >Compaq 386, PS/2-80, certain Sun-3, etc.) Not overly surprising. The Amiga's FFS is quite quick, and is part of a real time OS. My current drives, a 40 meg Atasi and a 70 meg Fujistsu, running off the SCSI port on a 2090A through two Adaptec 4000As, (two, because CBM does not provide support for LUNs in their driver yet) get 290K and 375K/second respectively, when they aren't fragmented badly (DiskPerfA, 32K buffer read figures). These same drives, running off the ST506 ports would probably get significantly lower numbers running off the ST506 port on the 2090A. Since they are ST506 drives, and since they transfer data across the drive/controller interface at the same rate (5 MBits/sec) regardless of the controller they are attached to, the difference is obviously in the controller. >ESDI is a modern, high speed interface, as is SCSI. "RAW" speed of both a >modern SCSI and an ESDI interface "should be" around 750KBytes/second, but this >is not achieved in practice (likely due to an OS and its filesystem) Remember, ESDI and SCSI are two different 'types' of interface. SCSI is the part that provides the interface between the host (computer) and the disk controller. ESDI provides an interface between the disk controller and the disk drive. The 'RAW' speed of an ESDI interface is 10 MBits/sec, and SCSI speed is dependent upon the handshaking from the host itself, up to a (spec'ed) maximum of 1.25 MBytes/second, more for extended SCSI, and in fact often more for standard SCSI, as there is nothing to stop a manufacturer from exceeding the SCSI max speed spec. As you can see, the limiting factor in the hardware, assuming every piece of that hardware runs as fast as it can, is the ESDI interface itself. In practice, however, the bottleneck, from a hardware point of view, is more often than not the disk controller itself, and these are definitely not all created equal. >The point I wanted to make is that any cost savings (of an ESDI) drive would >be negated simply by the need to purchase a translator (such as Adaptec's) and >that one would not see any performance gains; the embedded SCSI drives >themselves are extremely fast. Thus, the $200 saved (getting, for example, a >Maxtor XT-4380 ESDI drive instead of the XT-3380 SCSI drive) are "lost" by the >need to get a SCSI translator with attendant power cabling, ESDI cabling and >connectors, etc. (plus having one more "box" in the chain (the translator) as >a source of potential problems (interface, reliability, whatever...)). Embedded SCSI drives are also not all created equal. All that has been done with the embedded SCSI drives is that the functions of the disk controller have been moved inboard to the drive, effectively 'hiding' the controller/drive interface completely. The controller/drive interface can be anything from ST506 (probably never dne, but I don't know for sure), to ESDI (fairly common), to a prorietary and completely non-standard interface running at a higher data rate than ESDI (I suspect a few of the fastest drives do it this way). You cite the case of a Maxtor XT-4380 ESDI vs. an XT-3380 SCSI drive, neither of which I am familiar with, but can make some general comments about. It's a fairly safe assumption that drives from the same company, with the same mechanism, and having the same capacity, one being embedded SCSI and the other being ESDI, are both operating with the same ESDI controller/drive interface (it doesn't make economic sense to do it otherwise). So.... why the difference in performance? In a word, the controller, or as you called it, the SCSI:ESDI 'translator'. To compare the one embedded in the SCSI drive with the Adaptec is a valid comparison, but it only serves to compare two controllers. Believe me, there _are_ faster controllers out there. The Emulex MD-21 comes immediately to mind, and there are probably others. The real beauty of embedded SCSI is that a manufacturer does not have to stick with any controller/drive interface, and can do things out there in the way that will net the best performance. I have always wanted to see, for example, an 8 data head drive that stores 1 bit position per track, making the sectors 1/8 the length (in time of rotation), and of course coming in 8 times faster. With embedded SCSI, this is possible, and may already be done in one or more drives. Without the need for compatibility with other controllers, nifty things can be done. >Most of the people I know who've added ESDI drives to their Amigas have done >so solely because either "the drives were available at work" or "I got the >drive on an indefinite loan." For THOSE people, it did make economic sense >to use the ESDI drive. To date, I'm not aware of anyone making a "native" >ESDI interface for the Amiga and, due to SCSI's other advantages, I don't >foresee anyone doing so on a commercial basis (making an ESDI interface,that is) I agree wholeheartedly with your cost evaluations, which I guess was the main thrust of your posting, but wanted to correct the view of SCSI vs. ESDI that it presented, as shown by this paragraph. Since SCSI and ESDI 'look at' two different parts of the chain between the host and drive, they are just not comparable. SCSI does not preclude ESDI, even when a drive has embedded SCSI. If by 'native' ESDI interface, you refer to something similar to the ST506 ports on a 2090A (or to something like the XT-style ST506 controllers), then it is quite likely that one will never be produced. If one were produced though, it could theoretically transfer data at the full rated speed of the ESDI interface, or even have a large buffer for caching data (as do many embedded SCSI drives). In short, it could perform at the same raw data rate as an embedded SCSI drive that happens to use ESDI in the controller/drive interface. >Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ] -larry [ somewhre in the wilds of the Great White Frozen North ] -- "Intelligent CPU? I thought you said Intel CPU!" -Anonymous IBM designer- +----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca or uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 | +----------------------------------------------------------------------+