| Title: | AMIGA NOTES |
| Notice: | Join us in the *NEW* conference - HYDRA::AMIGA_V2 |
| Moderator: | HYDRA::MOORE |
| Created: | Sat Apr 26 1986 |
| Last Modified: | Wed Feb 05 1992 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 5378 |
| Total number of notes: | 38326 |
Can someone un-confuse me please? I've been looking into hooking an
RD51 (yes, the Decus type) to my A1000. Have gotten a lot of help from
other noters, but am still confused. There's the option of "SCSI host
controller"'s from Supra and C-Ltd, used with an Adaptec ACB4000 "SCSI
to ST506 adaptor". I've talked with mail order houses, along with
Supra and C-Ltd. What I originally thought was the scenario:
+-----------------+
| Amiga |
+-----------------+
||||||||||||
|86-pin bus| <- commands to controller
||||||||||||
+-----------------+
| Supra or C-Ltd |
| "SCSI host |
| controller" |
+-----------------+
||||||||||||
||SCSI bus|| <- commands to control hard disk
||||||||||||
+--------------------+
| Adaptec "SCSI |
| to ST-506 Adaptor" |
+--------------------+
||||| ||||||||
||ST-506 lines| <- commands to control hard disk,
||||| |||||||| converted from SCSI protocol to ST-506
||||| ||||||||
+---------------------+
| |
| ST412 hard disk |
| |
+---------------------+
This seemed to make sense to me, however:
1) Supra claims that they do not make a "SCSI host controller" for the
Amiga 1000, only a "SCSI host adaptor", which merely converts the
86-pin bus to SCSI. But, they did assure me that their "adaptor" comes
with software to format and use SCSI hard drives. Does this mean that
all "SCSI drives" come with the controller electronics built in?
2) The Adaptec ACB4000 board (which, btw no one seems to have in stock,
and all say over a month to get) is listed in the Computer Shopper as
an "MFM SCSI controller", rather than an adaptor. If this is indeed a
controller, and the C-Ltd is a controller, who's doing the controlling
here?
I've read claims for the C-Ltd SCSI whatever-it-is stating that you can
use it with "any SCSI drive". This seems to suggest that a "SCSI
drive" gets its controlling commands directly off of the SCSI bus,
so there is no "controller" per se. Am I getting warm?? :-(
P.S. An encouraging note for A1000 owners: Supra says they've been
swamped with a totally unexpected deluge of orders for their SCSI
whatever-they-are's for the A1000. Looks like there is enough of
an installed base of us out there such that we won't be totally
forgotten or ignored by Amiga manufacturers. :-)
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1427.1 | BAGELS::BRANNON | Dave Brannon | Wed May 18 1988 20:17 | 16 | |
yes, you're getting warm.
"controller" means different things to different folks.
the Amiga-to-SCSI adapter could be called the computer's SCSI bus
controller. I don't know the protocol, is SCSI master/slave or
peer-to-peer (i.e., does it actually control the bus or just talk
on it?)
the SCSI-to-ST506 adapter could be called the SCSI disk drive controller.
The idea is each SCSI interface is intelligent, you just need to
hook them together so they can talk SCSI protocol.
-dave
| |||||
| 1427.2 | Yet Another Surprise to Me | VTHRAX::KIP | Eschew obfuscation! | Thu May 19 1988 00:46 | 8 |
A friend of mine who works for a microcomputer hardware store in
Westboro told me that they sell a lot of "SCSI drives." He's handled a
lot of them and tells me that most them have a controller board built
in, which accepts SCSI input and sends *ST-506* to the drive itself!!
He said that a few of them he's seen actually have Adaptec boards (4000
or 4070) mounted right inside the drive.
"SCSI drives" my butt.
| |||||
| 1427.3 | some background | WJG::GUINEAU | Thu May 19 1988 09:47 | 54 | |
ST-506 is a dying breed. It requires significant intelligence in the controller to make these drives work. SCSI is an intelligent interface, requiring little (other than SCSI protocol) of the adapter. (My version) of the seperation of controller and adapter is this: HOST-->ADAPTER--->CONTROLLER----->DISK(HDA) Some systems do not require an adapter (like RQDX3 which is a QBUS (host) to ST506 CONTROLLER). The adapter is basically a transport/translation device. It takes the host bus and converts it to the storage system bus. The controller has some interface at the "host" side, and does all the HDA specific functions to the disk. There is confusion on SCSI devices these days, with respect to real SCSI or SCSI to ST506. Most "true" SCSI disks have "embedded controllers". This means that the drive has a SCSI interface on it (50 pin connector). Some vendors take ST506 and put a SCSI to ST506 controller card in between the disk and host. This is a marketing ploy to make customers think they're getting a SCSI interface disk/performance. When in reality there getting ST506 performance, slowed a bit by doing the SCSI to ST506 conversion. The only advantage is that now you can plug your ST506 drive into the same (SCSI) bus that your printer, tape drive, optical disk, etc.. is on. Now every disk has low level functions it must perform. (seek, read/write etc.). This is the level of ST506 (you (controller) tell it which direction to seek, which head to use, and you get raw data that must be phase lock looped on, data separated,and ECC'ed. SCSI, on the other hand, allows you to give it a READ command for LOGICAL BLOCK x, and length x. It does all the head cylinder, sector level stuff, and sends you back bytes of data. All in all, SCSI is the way to go for PC's. It's the most versitile bus of it's class with reasonable performance (up to 1.2 megabytes/second in async mode, 4-5 megabytes in synchronous mode - compared to st506 which is a 5 megaBIT/second interface (about 600Kbytes/second) And the older ST506 drives are real slow. some at 50-70 milliseconds average access! Newer disks are down around 20Ms and some at 17 or 18! John | |||||
| 1427.4 | Sassy (?? SASI ??) | CIMAMT::CROMACK | Tue Aug 16 1988 14:22 | 14 | |
I have a First Class Peripherals hard drive called "The Sider." Apparently it works with the Mac. I want to connect it to my Amiga. I talked to a First Class technician who said that the drive uses the "sassy" (?? SASI ??) interface, a subset of SCSI. The drive is a 20Mb drive which I got for free. It would be very nice if I could use it. Any suggestions? Dean P.S. I have an Amiga 1000 with 512K and 2 floppies. Nothing on the external port yet. | |||||
| 1427.5 | Might work? | WJG::GUINEAU | Fri Aug 19 1988 09:55 | 9 | |
Yup, SASI (Shugart Associates Storage Interconnect - or something like that) SCSI came from SASI. You'll need a SCSI adapter for the 1000, and make sure you get one that doesn't mind the limited vocabulary of SASI! John | |||||
| 1427.6 | Adaptek 4010 | CGFSV2::CADAMS | Clint Adams - Calgary, Canada | Wed Mar 01 1989 17:54 | 19 |
On the subject of adapters etc., does anyone know what an Adaptek
ACB-4010 is? I thought it was an old version of their ACB-4000A
(the newest model) but it seems that the ACB-4000A is the
replacement for the ACB-4000 and the ACB-4010. In the ACB-4000A
manual they talk about it being able to handle "hard sectored" and
"soft sectored/removable" devices (previously seperate
capabilities of the two older ACB-40X0 controllers).
I assume the ACB-4000 is for "hard sector" devices because that is
the one everyone seems to be using on the ST506 type drives. Does
that make the ACB-4010 for "soft sectored/removable" type drives
only rendering it useless for a normal ST506 type device.
If anyone has any old documentation on these old devices, I would
like to hear from them.
Regards..... Clint
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