ephraim@wang.UUCP (11/21/86)
Steve Brecher writes: > to: news@cit-vax.Caltech.Edu (Usenet netnews) > Subject: SCSI hard disks > > > Does anyone know what brand of drive is used for the major > > SCSI disc drives. i.e dataframe, Apple etc.. > > I would especially like to know what drive apple uses since > > their drive is said to support filetags. > > File tag support is a function of the controller rather than of the drive > itself. The Apple HD20SC uses a Seagate 225N with embedded controller; it > probably has custom ROMs to support tags. It does support tags, 'though Apple > has indicated that tags will probably not be supported by future products. This is very misleading. The only thing that the controller provides for tag support is funny-sized sectors. For HFS tags support, 512 data bytes plus 20 tag bytes = 532 bytes/sector. The ST 225N *does not* need custom ROMs to do this. The current firmware supports unusual sector sizes as a standard feature. Some other disks provide at least as much support. The Rodime RO 651 and 652, for example, support *any* sector size from 128 to 1024 bytes. Most of the work in providing sector tags falls to the disk driver in the Mac. When writing, the tags have to be retrieved from low memory globals (for the first sector) or calculated (for successive sectors of a multi-sector write) and inserted in the data stream. When reading, the tags have to be stripped out and the last set (from a multi-sector read) deposited in the globals. Apple Tech Support, BTW, is actively *discouraging* developers from supporting tags. They will not answer technical questions about them and say that Apple may drop tag support in future products. Ephraim Vishniac decvax!wanginst!wang!ephraim
ix21@sdcc6.ucsd.EDU (David Whiteman) (11/24/86)
Steve Becher states that the Seagate 225N drive, the drive used in Apple's SCSI HD-20 may need custom ROMS in order to implement file tags in an article in Delphi Digest V2 #52. Ephraim Vishniac states also in a previous article that this drive does not need custom roms for this function as it already has this capabity. All one needs for file tags with a Segate 225N drive is Apples software. I was playing with MacMate drive which is sold by Relax Technologies in Union City. All this drive contains is a power supply, a Seagate 225N drive and a very cheap case. I tried just out of fun to initialize the drive with the floppy that came with the Apple HD20 SCSI. The MacMate drive formatted and initialized without any difficulty, and Fedit Plus confirmed that this drive now had file tags, which it did not when previously formatted with the MacMate software. Another problem is that for some reason the MacMate software won't reformat the drive, but the experiment proves that the Seagate 225N drive does not need special ROMS for file tags. By the way I can not recommend the Mac Mate drive several of my friends had problems with them and received less than satisfactory help with their problems from the manufacturer. Apparently the drive is marked with a serial number internally on the drive when it leaves the company, and the enclosed software will not initialize the drive if it does not match the serial number. Their initialization software comes on the drive itself, and not on any enclosed software. So if you don't think of copying the program or if you buy two drives and only copy the program off one drive, if you want to reformat a drive you cant. They won't send you a copy of the format program. You have to send them back the drive, so they can format it and inscribe a new serial number. Of course this is not covered by the warranty because it is your fault for not knowing that each drive has its very own formatting program Also their driver will not recognize another company's driver, nor will it mount if another company's driver is used on startup; unless you pay $15 for an upgrade of the driver. Of course you will not have these problems if you buy the drive and then use Apple's software. Another thing about file tags: the only 3rd party company who has drives that will be supporting file tags is Levco. -- David Whiteman, University of California, San Diego The America's Cup, don't leave Perth without it.