16 Bit SCSI Host Adapter  (250-4161)     Versions       Faxback Doc. # 5084

There are currently 4 different versions of the 250-4161 board.  They are the
250-4161, 250-4161A, 250-4161B, and the 250-4161C.  The way to tell them 
apart is as follows.


250-4161:  This was the first board Tandy sold.  This board will run in
asynchronous mode only (J1, pin pair 1 must be off.  The large surface mount
IC at position U20 will be marked as AIC-6250.

250-4161A:  This was the second version Tandy sold.  It looks essentially
identical to the 250-4161 except that (1) J1, pin pair 1 is jumpered, which
means it can run in synchronous mode; and (2) the large surface mount IC at
position U20 is marked AIC-6250DL.

┌─────────────────────────────────────────────────────────────────────┐
│                                   LED           J1           ┌┐F1   │
│   ┌─────────┐                      ┌┐   ┌─────────────────┐  └┘     │
│   │         │                      └┘   └─────────────────┘ ┌─┐     │
└─┐ │ BIOS    │                                               │S│A    │
  │ │         │                                               │ │D    │
  │ └─────────┘                                               │C│A    │
  │                                                RN6┌─────┐ │ │P    │
  │                                           J4      └─────┘ │S│T    │
  │              J6                          ┌──┐  RN7┌─────┐ │ │E    │
  │     J5┌┐   ┌───┐           J8            └──┘     └─────┘ │I│R    │
  │       └┘   ├───┤        ┌──────┐       ┌──────┐           │ │     │
  │            └───┘J7      └──────┘       └──────┘      ┌┐   └─┘     │
  └────────────────┐               ┌────┐     J9      J10││   ┌───────┘
                   │               │    │                └┘   │
                   └───────────────┘    └─────────────────────┘
Figure 1. 250-4161 and 250-4161A


25-4161B:  This is the third version of the board.  It is quite different
from the 250-4161 and 250-4161A.  Most IC's are surface mounted, the jumpers
are different and there is an external connector on the back of the board.
This board, like the 250-4161A, is capable of synchronous mode and is
jumpered as such.

                                                                  ┌───
                                                                  │
┌─────────────────────────────────────────────────────────────────┼───┐
│                                  ┌┐      ┌───────────────────┐  │E C│
│                                  ││      └───────────────────┘  │X O│
│                                  ││       SCSI ADAPTER          │T N│
│                               J1 ││      ┌────┐ ┌────┐ ┌────┐   │E N│
│                                  ││      └────┘ └────┘ └────┘   │R E│
│   J9                             ││       RN3    RN4     RN5 ┌─┐│N C│
│  ┌───┐                           ││        ┌────┐  ┌────┐    │ ││A T│
│  └───┘  J11                      └┘        └────┘  └────┘  F1│ ││L O│
│        ┌───┐                                 J6      J7      └─┘│  R│
│        └───┘  J14 J15          J16                       ┌─┐    │   │
│              ┌───┬───┐        ┌───┐                   J10│ │    │   │
│              └───┴───┘        └───┘                      └─┘    │   │
└──────────────────┐               ┌────┐                         ├───┘
                   │               │    │                         │
                   └───────────────┘    └─────────────────────────┤
                                                                  │
Figure 2. 250-4161B

25-4161C:  This is the fourth version of the board.  It is completely
different from the other three, being shorter, having an external
connector, and being capable of synchronous mode.


┌───────────────────────────────────────────────────────┐
│   ┌───┐             LED┌┐  ┌─────────────────┐   F1┌┐ │
│   └───┘                └┘  └─────────────────┘     └┘ │
│    J3                       SCSI ADAPTER              │
│                             ┌─────┐      ┌───┐        ├──┐
│                          RN2└─────┘┌────┐└───┘        │EC│
│                                 RN5└────┘  RN3        │XO│
│                           J5 ┌──────────┐         ┌─┐ │TN│
│                              └──────────┘         │ │ │EN│
│                           J6 ┌──────┐          J7 │ │ │RE│
│                              └──────┘             │ │ │NC│
│                                                   └─┘ │AT│
│                J9                                     │LO│
│           ┌───────────┐                               │ R│
│           └───────────┘                               ├──┘
└───────────┐          ┌────────┐                   ┌───┘
            │          │        │                   │
            └──────────┘        └───────────────────┘
Figure 3.  250-4161C

────────────────────────────────────────────────────────────────────────────

(SMM/jlc-03/27/94)