sl@van-bc.UUCP (07/17/86)
Relay-Version: version B 2.10.1 6/24/83; site van-bc.UUCP Posting-Version: version B 2.10.1 6/24/83; site van-bc.UUCP Path: van-bc!sl From: sl@van-bc.UUCP (Stuart Lynne @ SLI) Newsgroups: net.micro.mac Subject: Re: Make A Mac+ Hard Drive Question Message-ID: <105@van-bc.UUCP> Date: Thu, 17-Jul-86 00:26:47 PDT Article-I.D.: van-bc.105 Posted: Thu Jul 17 00:26:47 1986 Date-Received: Thu, 17-Jul-86 00:26:47 PDT References: <541@hope.UUCP> Reply-To: sl@unix.UUCP (Stuart Lynne @ SLI) Distribution: net Organization: SLI, Vancouver, BC Lines: 112 Summary: In article <541@hope.UUCP> deano@hope.UUCP writes: > The Challenge of the week.... >. > I understand that it is fairly simple to hook up a Hard Disk to >the MAC+ SCSI Port. The Way I understand it is... >. >1. Get an off the shelf hard drive at your local electronics surplus. >2. Hook a SCSI Disk controller to the drive. >3. Hook the controller to the MAC+ SCSI port (custom cable?) >4. Tell the Mac that there is a H.D. (modify H.D. 20 DOC.?) >5. format dialog should magically appear, and your on your way. >. It's even easier. To assemble the hardware. 1. Buy an off the shelf case & PS for about $50 2. Buy a Seagate ST225N (specify rev 9 firmware) for about $450 3. Make a small cable with 50 pin header and 50 pin amphenol connectors 4. Bolt together case, PS and drive. 5. Connect to Mac+ with Apple System Cable and adapter cable. Total cost should be around $550. I got all my stuff in Canada so I can't be sure about US prices. Hamilton Avnet has a good supply of these drives with nationwide offices. You may be able to get a better price if you live in an area where you can shop around. Software is a little harder. I have the Apple SCSI software but don't use it. I think it will work with above hardware with a little work. The release I have does have some obvious errors, and some extra code is required to make the Seagate work properly. Specifically the Seagate has a problem with "Unit Attention". When the Mac is reset the SCSI bus is reset. The Seagate goes into a Unit Attention state. The Mac+ ROM does not know how to cope and cannot boot off the drive. Turning the drive on and off (several times) will eventually allow Mac to boot from the drive. With newer drives (rev 9 firmware does work) use the Mode Select command to set turn the Unit Attention "feature" off. This needs to be done only once (at the same time you format the drive is appropriate). Be sure to specify that you need at least rev 9 firmware. There are a bunch of the older drives in the field. If you do get one ask to have it sent back to the factory to get new firmware. One glaring bug in the Apple software is on page 10 (3/28/86 3:16 PM listing). The fifth line is move.l #512,SCArg2+2(a0) This should read: move #512,SCArg2+2(a0) or move.l #512,SCArg2(a0) Also the the description of the drivers capabilities don't exactly match reality. For example it doesn't hanlde multiple drives correctly. As I remember you end up with multiple copies of the driver in memory, one for each drive. I didn't spend a lot of time playing with their software, I just needed the parameters to the boot/init routine and thats how the published the info. Once the drive is formatted just mount the drive and the Mac OS will be quite happy to put an HFS file system on it for you (you must support the proper control calls to tell it how big the drive is). The Seagate is fairly fast (around 40ms average seek). Any faster would be wasted on the Mac. The main limitation is data transfer. Using the best case, a fast blind transfer will still only allow you to format with a 2:1 interleave (not Apples routines, they will only get you 3:1). The Seagate is a half height drive and not unduly noisy. I've run two of them on my desk without a case without being to annoyed at the noise. In a case under the desk, and you'll forget it's on. Speed seems to be better than Hyperdrive. Although I've only done some very quick rough and ready benchmarks. For example time to duplicate 1MB of files on the Hyperdrive 20 under MFS was about 32 secs. On Seagate with HFS was about 24 secs. All in all the drive seems to be fairly reliable, fast, and very inexpensive. (The only data loss I've encountered was due to user incompatence, and I'm the only user!) There are other SCSI compatible drives about to come onto the market. Priam with a 60MB, Quantum 80MB, Maxtor 240MB, CDC 240MB, etc. For the most part embedded SCSI will simplify your life when you write the driver (for example no need to tell the controller about the disk geometry, its in it's firmware so just say format and away you go). Also embedded SCSI is allowing the manufacturers to lower their prices by improving their production yields. (Because they handle the format, they can use advanced slip sector techniques to eliminate bad sectors, allowing them to use what would have been a bad platter if it had been put into a 506 style drive.) It also allows them to use RLL encoding or other techniques to increase the storage without adding extra heads/platters. Priam uses this technique to make a 60MB SCSI out of a 40MB ST506 drive. So we should see an avalanche of large, cheap SCSI drives in the final quarter 1986. Stuart Lynne ihpn4!alberta!ubc-vision!van-bc!sl 604-937-7532 Disclaimer ========== I am not in any way associated with either Seagate Technologies Hamilton Avnet, other than having purchased several drives from them. I am not associated with any of the other disk drive manufactures mentioned in this article and have not used their products.