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           Dr. Ken's Roll-Your-Own Vanilla SCSI Hard Disk Drive

                        by Dr. Kenneth Buchholz

NOTE:  Since this was written, some things have changed.  My comments are
enclosed within brackets ([]) to bring you up to date.  Otherwise, this text
is STILL the 'bible' on how to 'do-it-yourself'.  I've built about 10 hard
drives, SCSI & SASI, and it's very easy.  I claim credit for none of this,
other than my updates.  Ken deserves all the thanks!  <GG>


     With the advent of cheaper memory, larger software and especially the
Apple IIgs, Apple // computer users are using their systems for more complex
and larger tasks resulting in greater demands for high capacity disk storage
systems.  Since the birth of the Apple ][, we have seen changes in disk storage
from the original 13-sectored 5.25 inch floppy drive, to the 16-sectored 5.25
inch floppy drive (160K maximum capacity), to 3.5 inch micro floppy (800K
maximum capacity) to the rise in popularity of hard disk drives from 5
megabytes capacity on up.  These changing demands are not Apple //-specific but
are common throughout the industry, and the advances in hard disk drive
technology have been coupled with ever-decreasing costs.  Where once a hard
drive was the property of the wealthy few, more and more "home users" are
finding hard drives are no longer dreams of their futures but realities in
their dens and living rooms.

     When I purchased my Sider 10 meg SASI hard drive in April 1986, I paid
$695 "mail order".  When I purchased my 60 meg CMS SD60 A2S SCSI hard drive in
January 1988, the mail order price was $950.  As you can see, the price per
megabyte storage decreased from 69.50/meg to $15.83/meg - quite a price
decrease!  And although the price of commercial hard drives has not decreased
very much in the year since I purchased the CMS drive, you can easily assemble
your own SCSI hard drive at a cost of about $10.93/meg for a 64 meg SCSI drive!
I'll explain how (and how easy) it is in this document.

                            Why a SCSI Drive?

     For Apple // owners, there are basically two types of hard disk drives
which are popular: SASI and SCSI.  And example of a SASI drive is the Sider
series by First Class Peripherals (formerly XEBEC), and examples of the SCSI
drive are the CMS, Chinook and Apple hard drives.

     The SCSI (Small Computer Systems Interface) hard drives are by far the
most popular devices these days, especially in light of Apple's committment to
the SCSI interface (also used on the Mac line).  The SCSI interface allows you
to chain several SCSI devices [HDs, tape backups & CD-ROMs] on the same
"chain", and both ProDOS and GS/OS were designed with the SCSI interface in
mind.  To keep pace with future design advances in CPU and software, it is
highly recommended that you choose the SCSI interface type hard drives for your

                  Which Brand SCSI Hard Drive Do I Choose?

     There are several manufacturers of SCSI hard drives of excellent quality:
Seagate and MiniScribe are, in my opinion, two of the best around.  Both
manufacturers market a wide array of drive types (SCSI, MFM, RLL), capacities
(10-345 megs) and speeds (65-19 milliseconds) and provide very high quality
products backed by a 1-year manufacturer's warranty.  The CMS drives, for
example, use the Seagate SCSI series of drives in their products.
[Addendum:  Connor, Rodime, Quantum, Imprimis are all much better than the
drives mentioned above.  Basically, anything 'true' SCSI will work for this

     When searching for a SCSI hard drive, the first thing you need to know is
how to identify a SCSI drive from another interface type (such as MFM or RLL).
Seagate's SCSI hard drives are identified by numbers beginning with "ST" and
ending in "N"; for example, the Seagate 20 meg SCSI drive is identified by
ST255N, their 40 meg SCSI drive by ST251N and their 65 meg drive by ST277N.
MiniScibe identifies their SCSI hard drives by a 4-digit number followed by
"S"; their 20 meg drive is identified by 8425S and their 40 meg drive by 8051S.
[And you can always just ask your dealer.]

                      Which Size Drive Do I Choose?

     Which drive you choose depends upon several personal factors, such as
total storage capacity you need and the types of applications you'll be running
at present, what you think your future needs will be, and how much money you
can afford to spend right now.

     Your present needs and applications are the easiest thing to determine.
Consider how many 800K micro floppies and 160K 5.25 inch floppies you have as
"work disks" (vs backups) and calculate the total storage capacity that all of
these collectively take to get a rough idea as to what your present hard drive
useage would be.  Consider how fast you accumulate disks - 10 per month, 50 per
month?  Most of your disk accumulations should be for data, since most folks do
not accumulate program disks anywhere near as fast as they do data disks. 
Next, consider which of all your programs you would actually be running off the
hard drive.  Note that many games are copy-protected and thus can not readily
be moved to hard disk unless (a) you can remove the copy protection (or in rare
cases, the copy protection only applies to floppy copies and the copy protected
program can be moved to high capacity storage devices) and (b) the program was
written such that it is not dependent upon a specific volume name "hard coded"
into the program itself (if it does require a specific volume name, even when
run off the hard drive, it will require the floppy to be in the drive and will
most likely use that version rather than your hard drive version).  All of
these considerations are guidelines for getting some rough idea as to your
current hard drive needs; the bottom line is that you will have to give serious
thought to exactly what it is you'll be putting on your hard drive.

     The hardest thing to determine is what your future hard drive needs will
be.  This is especially difficult because, in many regards, the requirements of
future software applications is not only out of your hands but remains unknown
to even the developers themselves!  If you are using an Apple IIgs, about all
that can be said is that software is growing at an unbelievable rate and even
now many IIgs-specific products come on multiple 800K microfloppies.  Look to
the Mac and MS-DOS and OS/2 worlds to get a taste in the trends: single
applications requiring a dozen or more high density floppies are not uncommon
by any stretch of the imagination.

     Just like buying a new car, determining what you can afford on a new hard
drive is extremely difficult in large part because the cost per megabyte of
storage decreases dramatically as the overall capacity of the drive increases.
For example, ComputAbility's prices for Seagate SCSI hard drives in February
1989 were $319 for 20 megs and $419 for 65 megs: $15.95 per meg vs $6.45 per
meg.  Considering the per meg cost, it really does pay to stretch your wallet
to the max and get the largest hard drive you can possibly afford if you're
looking for both the best dollar value and the maximum expandability for the
future.  [These prices are VERY old.  You can find drives very cheap now. 
Check magazines like Computer Shopper, and Mac & IBM magazines.  SCSI is SCSI,
and many mail order houses advertise in the Mac/IBM mags, at cut-throat

     Finally, consider the sizes of the data files with which you'll be
working, and their number.  Many database programs, for example, use "virtual
memory" - using the disk in lieu of RAM memory.  An example of such an
application is Managing Your Money.  Applications which use virtual memory
require not only disk space for the file but more (which can be double the size
of the disk file itself) for virtual memory.  Again, there is no global
rule-of-thumb for this - it varies from user to user based on specific software
applications running and the amounts of data being maintained and manipulated.

                      What Speed Drive Do I Need?

     To the greatest majority of folks, Speed Is King.  In addition to large
storage capacity (and the concomitant elimination of constant swapping of
floppy disks during your application), hard disk drives offer great
improvements over floppies in I/O (input/output) times.  Several factors play a
role in the effective I/O speed of the device: seek time (how fast the drive
itself can find specific blocks on the disk surface), transfer rates (how fast
the data can be moved between drive and computer), and CPU speed (how fast your
computer can handle data movememts within itself).

     "Slow" hard drives have a speed of approximately 60 msec or greater.
"Fast" hard drives have speeds in the range of 18-28 msec.  The most common
"average" SCSI hard drives operate in the 40-42 msec range. [Most 'common'
drives now run at 23ms - Access times DO make a difference.]  Of course, you
pay for increased speed (nothing is free in life), and to give you a rough idea
of how much you pay for the speed increase, consider these prices from Hard
Drives International on identical type (non-SCSI) and sized drives which differ
ONLY in access speeds: the Seagate ST251 40 meg drive at 40 msec runs $329
whereas the exact same drive running at 28 msec is $399.  That's $1.75/meg
added to the cost for increased speed alone.
     The most popular speed today on the Apple // series is 40 msec since
neither the CPU nor the host adapter cards (plugged into the Apple's slots and
connected to the hard drive itself) can handle drives much faster than this. 
[This is no longer the case. My Wren III runs at 19ms, and works on any
current SCSI interface, and on a IIe & IIgs without a problem!] Of course, this
will change in the future, but for now spending more money on drives faster
than 40 msec does not give you any direct benefit. [Yes, it does.] If today is
your main concern, you are better off spending the extra dollars to get a
larger capacity drive; if you are concerned with tomorrow as well, and speed is
your main concern, getting the faster drive today may pay off in the near
future.  About the only other suggestion I can offer is to NOT get a drive
slower than 40 msec (i.e., an access time whose number is greater than 40,
e.g., 65 msec).  [I agree!]

                     Rolling My Own - A Short History

     Last year, when my BBS needed to expand its hard drive storage beyond the
10 megs it had, I was faced with again spending $950 for another commercially-
available 60 meg hard disk drive.  And my pockets just weren't that deep,
especially after having blown $950 several months earlier.  I was also
somewhat green with envy at all my MS-DOS friends (yes, I admit it - I do have
MS-DOS friends!) constantly bragging about just how cheap their hardware was.
These were the circumstances which lead me to buy my first copy of Computer
Shopper and thus began my journey into the unknown world of assembling my own
vanilla SCSI hard disk drive.

     Having a CMS drive already, I popped open the hood and looked inside.  I
found that the CMS hard drive - once mysterious and magical - was nothing more
than a Seagate ST277N SCSI drive and power supply unit inside a metal box.  It
appeared that CMS did no alterations whatsoever to the Seagate drive itself;
that is, all of the interfacing to my Apple IIgs was done via their SCSI Host
Adapter card which plugs into a slot inside the Apple itself.  Time to call in
my chips with all my contacts in the industry, so off I went through
CompuServe, GEnie, a series of telephone calls and numerous letters.  To my
surprise, no-one seemed to know if my assumptions about the CMS were correct. 
I was on my own, with a lot of "Best wishes and let me know how you make out!"

     I obtained a loaner Seagate ST277N in plain, no-frills case with power
supply.  I replaced my CMS drive with this generic drive and booted the system.
After several attempts, I got it to work flawlessly off the CMS SCSI Host
Adapter.  My suspicions were indeed true!

     Out came the Computer Shopper and in went my orders to vendors.  Here's
the hardware I went with and highly recommend:

                             Hardware Required

     - Seagate STxxxN SCSI hard drive.  I used the exactly same 65 meg drive
that CMS uses in their 60 meg SD60 A2S model (the difference in size is
explained below; the drive itself is indeed 65 megs unformatted capacity).

     - The Tulin Apple Hive case with 30 meg power supply, fan and all internal
cables and hardware.  [A truely good unit, but shop around.  There's LOTS of
cases available now.  You can even build this into a dead Sider or other HD

     - The CMS SCSI Host Adapter Card with external cable and formatting
software.  [Terrible.  Get either a (old) Apple Rev C SCSI, or the new Apple
HS-SCSI (high-speed), but I HIGHLY recommend the RamFAST SCSI. Tremendously
fast, and going for as little as $75 more than the Apple card. RamFAST is made
by CV Technologies: 1800 E.Whipp Rd. Suite 200, Kettering, OH 45440. (513)
435-5743.  Most mail-order houses carry them now.]

     As of the February 1989 advertised prices in Computer Shopper, this same
drive subsystem will run approximately $653 without shipping if you use the
ST277N model (65 megs).  I supply a list of vendors and February 1989
advertised prices at the end of this document; you can bargain hunt through
Computer Shopper and local computer faires and flea markets and save a few
extra dollars if Lady Luck is on your side.

                                The Roll

     Assembly is truly a piece of cake if you have mastered the fine art of
using a Phillipshead screwdriver, and total hardware assembly time is less than
5 minutes (taking your time).  Since all cases are basically identical in terms
of assembly of the unit, I will be relying upon my personal experience using
the Tulin Apple Hive here.

     Secure the Seagate drive to the base of the case using the supplied 4
screws and tighten securely but be careful not to exert too much torque (if
this is at all possible).  Take one of the two power cables coming from the
power supply and plug it into the back of the drive itself.  The power line
terminates in a D-shaped male connector which plugs into a D-shaped female
socket on the back of the drive; the D-shape prevents you from plugging the
power cable into the drive in the wrong orientation, so this is fool-proof. 
Next, plug the cable coming from the twin DB-25 pin connectors on the back of
the case into the drive.  This cable terminates in a 50-pin connector.  Examine
this connector closely and you will note that there is a guide on it which will
allow you to insert it onto the connected on the back of the drive ONLY in the
proper orientation, so you can't possibly install this cable wrong.  Next,
examine the 4 sets of pins on the lower left back side of the drive itself.  If
any of these pairs have jumpers (small black plastic tabs which slide over a
pair of pins), remove them.  Without too much discussion on their function,
suffice it to say that without any of these pin sets "jumped", the drive will
have a device number of 0 (zero).  [This is ok, as long as the hard drive
is the ONLY SCSI device online.  Otherwise, you'll have to give it an ID
to keep it from interfering with other SCSI devices on the bus.]  Next, connect
the two single-stranded lines running from the power supply to the green LED
light on the front of the case.  This light is the power ON/OFF indicator. 
Finally, replace the top of the case, securing to the base with the 3 screws
provided, and insert the external power cord into the back of the case (but
don't plug it into the wall just yet).  Assembly of your hard drive system is
now complete and ready for attachment to your Apple //.
     How you interface your SCSI to your Apple depends upon the specific host
adapter card you are using.  In this example, I'm using the CMS SCSI Host
Adapter card; if you are using another brand card, follow the manufacturer's
directions for setting up the card.  You will need to know that your hard drive
has a device number of 0 (zero).
     The CMS card is configured using jumpers (exactly like those which may
have been on the back of your Seagate drive that you removed).  These jumpers
control such things as capacity of the drive, volume partitions (start
locations and size), device number, etc.  Note that GS/OS will allow you to
access volumes greater than 32 megabytes but if you are using any ProDOS-8 or
ProDOS-16 applications, you must partition your drive so that no single volume
exceeds the ProDOS limitation of 32 meg maximum volume size.  Thus, in this
example, we'll be partitioning the drive into 2 30 meg volumes.
[None of the following paragraph matters to you unless you're running a CMS
SCSI card.  (Why are you?)]
     The CMS card has 6 banks of 8 pairs of jumpers to control Device ID (DID),
Host ID (HID), Partition Starting Point and Size (PS1 and SZ1) for the first
partition and Partition Starting Point and Size (PS2 and SZ2) for the second
partition.  Since we set our drive to a device ID (DID) of zero, none of the
pin pairs should be jumped.  To select a host ID (HID) of 7, the first 4 pin
pairs (1-4) should be jumped and the last 4 pin pairs (5-8) should be open. 
Our first partition will start at a location of zero and be 30 meg in size, so
the jumper settings for PS1 should be all open (none jumped) and SZ1 should
have jumpers ONLY on pin pairs 1, 3, 4 and 5 (pin pairs 2, 6, 7 and 8 should be
open).  The second partition will begin at location 30 and be 30 megs in size,
so the jumper settings to accomplish this are PS2 should have a jumper ONLY on
pin pair 4 (all others are open) and SZ2 should have jumpers on pin pairs 1, 3,
4 and 5 ONLY (2, 6, 7 and 8 are open).
     Having set the card for the correct configuration, insert the card into an
open slot in your Apple // (6 or 7 is preferred), connect the short ribbon
cable coming from the card to the back of the // at an open panel in the back
plate.  Connect one end of the heavy- shielded cable supplied with the host
adapter card to the DB-25 connector at the back of the Apple and the other end
to one of the two (either one) DB-25 connectors on the back of the Apple Hive
case.  Make sure all connections are secure.  Plug the hard drive power cord
into a wall socket and turn the hard drive ON using the ON/OFF switch on the
front of the Apple Hive case.  Put the utilities disk supplied with the host
adapter card into your floppy drive and boot your computer.
     Before you can use your hard drive, you must perform two tasks.  One is
the "low level" formatting of the disk surface itself.  The software to do this
is supplied on the CMS utilities disk that comes with the Host Adapter card. 
The other task is the ProDOS formatting of the drive, which is done after the
low level formatting.
[On a IIgs, you can use Advanced Disk Utility to format this drive.  The
Chinook SCSI Utilities are a great set too, and there's SCSI.Hacker and
HDFormat in the public domain/shareware world.  All are good.  On a RamFAST
SCSI interface, all the formatting/partitioning software is on the card. 
Another reason to use it!]
     Use the CMS Utilities Disk to low-level format the new drive surface. 
This will take several minutes to perform. [This will take a helluva long time
to perform on a very large drive!]  When done, it is an excellent idea (not
really an option in my opinion) to run the test procedure.  This test procedure
performs read/write activity on each and every block on the disk surface
repeatedly until you stop the test.  It takes quite a bit of time to do one
"pass" - that is, to read/write/verify every block on the disk - and it is
recommended you let this procedure do several passes.  Take the time to do
this, since the procedure will mark as "unavailable" those bad blocks it finds
and this will prevent you from loosing valuable data in the future.  Don't
worry if your system turns up several bad blocks - hard drives all have bad
blocks, and thus the manufacturers allow extra tracks on the disk for
replacement blocks.
     After the test for bad blocks has been performed, you can exit the
utilities and you're ready for the last step in preparing your hard drive for
use: the ProDOS formatting.  I use Prosel's CAT.DOCTOR utility exclusively
(more on this later) but any utility which allows you to ProDOS format a disk
will do.  [Do this no matter WHAT you low level formatted the drive with, just
to be safe!]
Run your ProDOS format utility and select S6D1 (assuming your hard drive host
adapter card is plugged into slot 6) for formatting.  You will see that this
takes less than 2 seconds to perform!  Next, select S6D2 for formatting.
Remember, we had to partition the drive into 2 30 meg volumes, and these are
mapped as Drive 1 and Drive 2 in the slot in which your host adapter card is
plugged into.  You can name each of these volumes with any valid ProDOS volume
name, such as /HARD1 and /HARD2.
     Congratulations!  Your hard drive is now fully ready to use.

                        Where Do I Order From?

     In addition to the vendors that I have purchased from, there are several
others advertising in Computer Shopper.  Here is a list, by no means
exhaustive, of some of the dozens of vendors selling various hardware you'll

     Hard Drives International (1-800-234-DISK) is an extremely reputable firm
dealing ONLY in hard drives.  HDI provides near rock bottom prices, usually
delivers quickly (if item is not out of stock), and provides a full technical
support team.  Here are prices for some of the more popular Seagate and
MiniScribe drives, as advertised in Computer Shopper February 1989:

[Prices removed here, as they were from 1989, and no longer current.]

     ComputAbility (1-800-558-0003) offers rock bottom prices:

[Same here...]

     Tulin Corporation (1-408-432-9025) provides an excellent case - sturdy and
quite attractive - in the Apple Hive.  The Apple Hive cases come complete with
power supply, fan and ALL internal hardware and cables necessary - you only
need to buy a drive.  They also now provide "kits" including everything (except
the SCSI host adapter card) needed:

          - Apple Hive with 30 watts power + fan $119
          - Apple Hive with 60 watts power + fan $169
          - 30 meg SCSI Drive System w/ Formatting Software $425
          - 40 meg SCSI Drive System w/ Formatting Software $489
          - 61 meg SCSI Drive System w/ Formatting Software $529

          * SCSI Drive Systems do NOT include host adapter card
          * Each Seagate SCSI drive (STxxxN) requires 12.5 watts power
               so the 30 watts Apple Hive will sufficiently power two
               hard drives.

     HardTimes (1-408-452-1929) offers an inexpensive alternative to the Apple
Hive case by Tulin.  The HardTimes case ($79) features a fan, 50 watts power
supply, brackets, room for 2 half-height or 1 full height drive and room for a
controller.  (*Note: the Seagate STxxxN drives contain a SCSI controller
embedded within the drive and do NOT require an external controller board.)

     CDA Computer Sales (1-800-526-5313) is an excellent source of SCSI host
adapter cards, both CMS and Apple.  Both brands run approximately $115.  CDA
provides excellent service and is reliable and priced competitively.

                          Alternative Life Styles

     You do NOT absolutely need to get a hard drive mechanism with SCSI
embedded.  Adaptec markets controller cards which allow you to use MFM or RLL
hard drives off an Apple SCSI host adapter.  The basis for this card (Adaptec
4000 series) is that the card is positioned between the drive mechanism itself
and the host adapter card in the link.  The non-SCSI drives generally can be
had for about $80 less than their SCSI counterparts, but then you need to shell
out approximately $100 for the Adaptec card; its therefore usually cheaper, and
a whole lot neater, to simply obtain a SCSI drive.  But if you're lucky enough
to obtain a non-SCSI drive for free, you can indeed use it with the proper
Adaptec card.  Hard Drives International is the best source of information on
the Adaptec cards, so give them a call.

                               Warren T.

     One of the most important questions (after "What is the price?") is "What
kind of warranty do I get?"  Most people are afraid to assemble their own
vanilla hard drive for fear that, unless they purchase a designer name brand
drive, they will be left out in the cold in terms of warranty.  Not so. Seagate
warranties all their drives for a period of 1 year; other manufacturers offer
similar warranties on their hard drives.  If you don't particularly like
dealing directly with the manufacturer, some vendors, such as Hard Drives
International, will provide a limited coverage in addition to that offered by
the manufacturer - simply return the defective drive to them within a certain
period of time and they will replace it.  After that, you must go directly to
the manufacturer.

     What about the case?  Well, the case is a non-mechanical item and short of
having an elephant stand on it or backing your pickup truck over it, there is
little that can go wrong with the case itself.  The internal power supply and
fan are something else, though: they are electronic components subject to wear,
tear and failure.  Tulin, for example, warranties their power supply and fan
for a period of 6 months.  If you decide to go with the HardTimes or other
brand case/power/fan, ask about the warranty BEFORE you purchase.  Should your
fan and/or power supply unit go out after the warranty expires, you can always
purchase a brand new replacement part inexpensively.  For example, replacement
power supplies run $35-$50, and since you are saving approximately $300 by
building your own hard drive to begin with, that savings can purchase a lot of
new replacement parts before you "break even".

                             Miss A. Laney

     If you opt for the HardTimes or other brand case, other than the Tulin
Apple Hive, you may be faced with needing to order a cable or some other
internal hardware.  Before you ask, tell the vendor exactly what you'll be
using the case for and ask what internal hardware (cables, brackets, etc.) is
provided and what is not provided (and thus what you will need to secure
elsewhere).  In this sense, the Tulin Apple Hive is the easiest, most
hassle-free case to get.  [Agreed, but perhaps not the cheapest.]

     In case you find the need to make your own cable, I provide the pinouts
below.  Seagate provides a short 50 line ribbon cable, terminating at both ends
in a 50-pin connector.  Thus, you may need to make (or otherwise obtain) a
heavy-shielded cable going from 50-pin at one end (drive end) down to DB-25 pin
at the other end (computer host adapter end).  If you're not good at soldering,
or simply faint-of-heart, Mytech (1-800-527-7435) might be able to provide you
with exactly the cable you need at extremely reasonable prices.

                     The Home Brewed External SCSI Cable

     The pinout needed for the SCSI external cable (host adapter to drive) is
as follows:

                                              Actual Pin Views
   From              To         ____________________________________________
DB-25 male     50-pin connector \                                          /
----------     ----------------  \ 1  2  3  4  5  6  7  8  9  10 11 12 13 /
   1                 48           \  14 15 16 17 18 19 20 21 22 23 24 25 /
   2                 42            \____________________________________/
   3                 50              ______
   4                 40             |      |
   5                 38             |1    2|  NOTE: all odd pins are
   6                 36             |3    4|        grounded on a SCSI
   7                  1*            |5    6|        50-pin connection
   8                  2             |7    8|
   9                  1*            |9   10|
  10                  8             |11  12|
  11                 12             |13  14|
  12                 14             |15  16|
  13                 16             |17  18|
  14                  1*            |19  20|
  15                 46             |21  22|
  16                  1*            |23  24|
  17                 32             |25  26|
  18                  1*            |27  28|
  19                 44             |29  30|
  20                 18             |31  32|
  21                  4             |33  34|
  22                  6             |35  36|
  23                 10             |37  38|
  24                  1*            |39  40|
  25                 NC             |41  42|
                                    |43  44|
NOTE: 1* implies a connection to    |45  46|
      1 or any other ODD pin/wire   |47  48|
      (which is GRND)               |49  50|

                         Apple II SCSI Card: Spec Sheet

I believe this spec sheet is directly from Apple Corporation, but can not
state that for sure.  It is something I pulled from one telecommunications
services but long forgot which one.  [This is for the older Rev C SCSI card]

I. Technical Specifications

     A. Hardware:

          -- Provides an electrical interface between external SCSI devices
             and the CPU.

          -- Provides the address and control lines required by the Apple
             II's microprocessor for accessing and controlling the SCSI chip
             and Smartport firmware.

          1. NCR 5380 SCSI IC
               a. Implements SCSI bus
               b. 5380 data sheet in Chapter 2 of the hardware technical
                  reference manual

          2. Other circuitry to interface the 5380 IC with the Apple II CPU
             control signals

          3. RAM:

              -- 8 banks of 1K
              -- Accessed with special logic circuits
              -- Used for status of devices at SCSI bus initialization
                 (including the status of the Apple II SCSI card itself)

          4. ROM:

               -- 8 banks of 1K
               -- Accessed with special logic circuits
               -- Used for storing Smartport firmware

          5. Interface: 25-pin SCSI connector

    B. Input/Output:

         -- Parallel transmission

         1. Two modes for data i/o operations:

              a. PDMA (pseudo-DMA)
                   -- default
              b. Block Move
                   -- only supported by 65816 CPUs
                   -- must be enabled by the application

         2. Maximum storage area under ProDOS: 32 megabytes

     C. Firmware: Smartport program

          -- converts the microprocessor commands or calls issued by CPU to
             format compatible with external SCSI devices

          -- issues calls to the microprocessor to give it the status of the
             external SCSI devices and allow the CPU to control their

          1. Commands supported: STATUS, READ BLOCK, WRITE BLOCK, FORMAT,

          2. Boot capablility with Autostart ROM when you install the card in
             the slot with highest priority, which may depend on the
             operating environment

               -- When Smartport does not find the SCSI device capable of
                  booting the system, Smartport returns control to the
                  environment of the Apple II and the boot search continues
                  through lower-priority slots.

      D. Electrical

           1. Voltage requirement: 4.75 to 5.25 volts DC

           2. Power consumption in milliamps (ma)
                a. Standby: 340 ma
                b. Operating: 390 ma

      E. Environmental

                                   Celsius   Fahrenheit
           1. Ambient temperature: 10 to 40  50 to 104

           2. Relative humidity: 20 to 95 percent (noncondensing)

II. System Configuration

      A. Cable: Apple SCSI System Cable

      B. One or more SCSI-compatible peripherals

         -- Can be a high-speed printer interface

         1. Daisy chaining

              -- Apple II with the card in slot 5 and no card in slot 2,
                 except a card for a serial printer or modem:

              a. Running ProDOS 1.2: 4 external devices
              b. Running ProDOS 16: 7 external devices

      C. Additional SCSI system components as required:

           1. Cable Terminator
           2. Peripheral Cables
           3. Cable Extenders

           -- Maximum total length of cables: 20 feet (6.5 meters)

           Important: Read the manual for the Apple SCSI Cable System
                      before trying to connect any devices

      D. Computer with disk drive

           -- Apple IIGS
           -- Apple IIe
           -- Apple II Plus
           -- Card fits into standard slot to connect to Apple II Internal
              bus for Apple II standard I/O and control (Slot 3 reserved for
              80 column capability)
|                                                                            |
|Contributed by: K. Buchholz & The Washington Towne Crier BBS    201-689-3649|

|                                                                           |
|  This updated version of VanillaHD by the sysop of the Bloom County BBS   |
|        (Which is running on a home-built 155mb Wren hard drive!)          |
|      You CAN do this yourself!  If I can help, contact me at the BBS or   |
|      on America Online:  AFC GaryG     Good luck!                         |
|                                                                           |
|      For the finest in PD, Shareware, and Demos, Call the County!         |
|                                                                           |
|Bloom County (313) 582-0888 - 3/12/24 - 24Hrs - PC Pursuit via /MIDET 12/24|
|                                                                           |
|       The Bloom County BBS..."The reason you bought a modem" (tm)         |


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