Iomega PC4B/50

@7FF9.ADF - IOMEGA PC4 Host Adapter Board 
@7FFA.ADF - IOMEGA PC4B/50 SCSI Host Adapter Board
@5FCB.ADF - IOMEGA PC4B/HD SCSI Host Adapter Board

iomega-pc4b50-v6.21-rom.bin    PC4B/50 ROM Requires 27C64A-25 [thx to Alex Perez]

NOTE: I lack any images of a PC4B/HD
5000 – 5FFF    Direct Memory Access (DMA) Devices
7000 – 7FFF    Storage *Multi-function adapters with storage typically respond as storage

IOMEGA turned over support for Bernoulli and Floptical products to Comet Enterprises

Bernoulli drivers
ioware9xdrv.exe Win 95/98 ver 1.0
iowarentdrv.exe Win NT 3.51 / 4.0 ver 1.0
dosdrvr.exe Win 3.1 / DOS  ver 1.0

OS2V234.EXE Iomega Tools for OS/2

DOS, All 5 1/4 Bernoulli drivers
SCSI303.EXE 
SCSI50.EXE  Supports Zip, Jaz, Bernoulli and Lasersafe

8" drives, DOS, drivers ("Alpha")
OAD1-33.ZIP  
rcddos.zip 

Floptical ?

FTP Iomega Software FTP  [It's dead, Jim]

PC4 BD#2 
ADF for PC4

PC4B/50
ADF for PC4B/50  

PC4B/50F

PC4B/HD [ADF only :( ]

IOMEGA Host Cable Pin-outs 

NCR 86C01 Snippets   


PC4  BD#2 0068300-0 


Full length, 16-bit card, left third has a buncha non populated positions. Uses NCR 53C90

 Was there a PC4 "BD#1" which used an NCR 5390? The 5390 to the best I can determine lacked DMA. Period articles [the very few] say the PC4 does not do DMA.

 No BIOS chip, GAL / PAL? Three soldered Resistor networks. No apparent jumpers. 50 pin shrouded internal header, DB37 external header.

My SWAG, the PC4B used a variant of 53C90 ?

Silkscreen upper right, "IOMEGA PC4 BD#2

Silkscreen by barcode: Geoduck by BC/MC/KM/RJ/SK

Adapter PC4
0068300-0
03-15-1988

FCCID: DDX7EBPC4

ADF Sections 07FF9h "IOMEGA PC4 Host Adapter Board"  

NumBytes 2

"I/O Address Select"
Use any one of the I/O Addresses listed. 'Disabled' causes the adapter to be inaccessible.
"240" [00240-0025F], 340 [00340-0035F], 400 [00400-0041F], 420 [00420-0043F], 3240 [03240-0325F], 8240 [08240-0825F], A240 [0A240-0A25F], "Disabled"

"DMA Level Select" 
The PC4 supports the DMA mode of data transfer. The lower the DMA level, the higher the  priority. DMA level 5 is recommended.

   "DMA Level 5", 6, 7

"Fairness"  
'Fairness' enabled, the PC4 won’t compete for the channel during the next arbitration phase if it is currently in control of the channel. Other installed adapters can obtain the channel in the next sequence based on each adapter's assigned priority level.
'Fairness' disabled, the adapter competes for every arbitration phase and obtains more than its fair share of channel usage. Recommend 'Fairness Enabled' for all adapters.

   "Fairness Enabled", "Fairness Disabled"

"Preempt Count Select"
When the PC4 detects that another adapter requires use of the channel, the Preempt Count feature is activated. The Preempt Count is the maximum number of bytes to transfer before yielding control of the channel. The PC4 always transfers a max of 7 bytes before relinquishing control of the channel. NOTE: Always ON, it appears...
   "7 Bytes"

NOTE: The little bit we have on the NCR 8601 has four settings, 0, 1, 3, and 7.

PC4, PC4A, PC4B, What's the Difference?
  Originally, "B" suffix interfaces had the BIOS ROM. The PC4 has no ability to take a BIOS. PC2, PC3, PC4 had no BIOS. When the PC4B was created, IOMEGA must of had considered how to differentiate between the more primitive PC4 and the more advanced PC4B. My SWAG, you see the silkscreen outline that says PC4B? It encircles the BIOS support chips. Components marked "A" or "PC4A" were most likely to provide electrical continuity for a non-BIOS configuration.


PC4B/50
J1 BIOS
J2 DB37 Male
J5 Termination?
RP1-3 Resistor paks
U1 BIOS 27C64A-25
U2 NCR 26C64L-10
U6 NCR 86C01 Interface
U7 NCR 01148000
U15 16.000 MHz osc
0

Image from Alex Perez


Notice the outlines marked "PC4A" and "PC4B" ? I've seen this on the BusLogic BT-646 S/D, where the SE version and the Differential version populate the call-outs as required...

J5 and CR1 provide TERMPWR.

"Bar Code Label" SK/KMI/JH "JH" like Jack Hoa from Future Domain?

IOMEGA identifies the card quite well on the sticker:
01046201-03  [P/N]
PC4B/50 10-02-90 [Model, Date]
S/N 4EC2HY  [S/N... Duh...]


Same PCB, it has an extension riveted on to the PC4B PCB, perhaps to aid air flow?

PC4B Interface Controller 
   The PC4B supports the following Iomega drive subsystems: 
MultiDisk 150 [B150] 
Bernoulli 20, 44, 90, 230
Floptical 21: 
LaserSafe, LaserSafe PRO: 

   The PC4 interface controller is an Iomega proprietary controller, not a SCSI controller. The PC4B will not support third party SCSI devices. The PC4B interface kit includes the 37 to 50 pin SCSI cable, OAD for DOS drivers, and Utility Users Manual. The PC4B controller may also be use with the OS/2, Unix, and Xenix operating systems. Addition drivers will be needed for any operating system other than DOS.
 
IBM Models 90 and 95 must have a hard drive installed before the PC4B controller will function. 

   If your computer has a fixed disk drive, the fixed disk drive should be used to boot your computer. The ROM on the Iomega PC4B adapter should be disabled.


AdapterId 7FFA Iomega PC4B/50 SCSI Host Adapter Board

I/O Address Select
   I/O address used by PC4B/50. 'Disabled' causes the adapter to be inaccessible.
      <"240" (io 00240h-0025Fh)>, 340 (0340-035F), 400 (0400-041F), 420 (0420-043F), 3240 (3240-325F), 8240 (8240-825F), A240 (A240-A25F), Disabled

DMA Level Select
   The PC4 supports the DMA mode of data transfer.  Most operating systems require this option to be enabled.  The lower the DMA level, the higher the priority.
      <"DMA Level 5">, 6, 7, DMA Disabled

Fairness
   If 'Fairness' is enabled, the PC4 adapter will not compete for the channel during the next arbitration phase if it is currently in control of the channel.  This allows other installed adapters to obtain the channel in the next sequence based on each adapter's assigned priority level.  When 'Fairness' is disabled, the adapter will compete for every arbitration phase and will obtain more than its fair share of channel usage. 
      <"Fairness Enabled">, Fairness Disabled

IRQ level
   Operation with multi-tasking operating systems may require the use of an IRQ signal when the PC4 requires processor service. No other adapter may be assigned the same IRQ level as the PC4. For DOS-only systems, this option may be disabled. 
      <"IRQ 7">, 5, 3, 9, IRQ Disabled

Memory Address Select
   You may set the PC4 adapter to any one of the Memory Addresses
listed.  The first choice is recommended for systems with a fixed
disk installed. 
      < "Disabled">, D400 (d400-d5ff), D200 (d200-d3ff), D000 (d000-d1ff), CE00 (ce00-cfff), CC00 (cc00-cdff), CA00 (ca00-cbff), C800 (c800-c9ff)

PC4B/50F ?


PC4B/HD

05FCBh "Iomega PC4B/HD SCSI Host Adapter Board"

NumBytes 4

FixedResources            pos[0]=00XXXXXXb   pos[1]=X11XXXXXb

"I/O Address Select" 
   "240", 340, 400, 420, 3240, 8240, A240, Disabled
Set the adapter to any of the I/O Addresses. The first choice is recommended. 'Disabled' causes the adapter to be inaccessible.

"DMA Level Select" 
The PC4 supports DMA mode of data transfer. Most O/Ss require this to be enabled.  The lower the DMA level, the higher the priority. If you have a hard disk installed, it is recommended that you select a DMA level higher than the hard disk.

   "DMA Level 7", 6, 5, DMA Disabled

"Fairness" 
"If 'Fairness' is enabled, the PC4 adapter will not compete for the channel during the next arbitration phase if it is currently in control of the channel. This allows other installed adapters to obtain the channel in the next sequence based on each adapter's assigned priority level. When 'Fairness' is disabled, the adapter will compete for every arbitration phase and will obtain more than its fair share of channel usage. We recommend you use 'Fairness Enabled' for all adapters.

   "Fairness Enabled", Fairness Disabled

"IRQ level" 
Operation with multi-tasking operating systems may require an IRQ when the PC4 requires processor service. No other adapter may be assigned the same IRQ level as the PC4. For DOS-only systems, this option may be disabled.

   IRQ 3, 5, 7, 9, or Disabled.

"Memory Address Select" 
The PC4 may use any of the Addresses listed. “Disabled” is recommended for systems with a fixed disk installed. If you want to boot from a device connected to your PC4, select the first available memory address and assign the device attached to the adapter the SCSI ID of zero. NOTE: Uses the clone 0,1 for boot devices !
NOTE: "Disabled"disables the BIOS ROM. Same as pulling the BIOS EPROM.

   "Disabled", DC00, D800, D400, D000, CC00, C800

"Termination Select" 
Sets termination ON or OFF. Default is ON. Turn termination OFF if you intend to use both the internal and external connectors.

   "ON", OFF

IOMEGA Host Cable Pin-outs  Original HERE on Internet Archive

SIGNAL    50 PIN  50 PIN  37 PIN  25 PIN  50 PIN
NAME      Cntrncs Ribbon  D-Shell D-Shell SCSI2/HD

DB0          26      2       37       8       6
DBI          27      4       36      21       7
DB2          28      6       35      22       8
DB3          29      8       34      10       9
DB4          30     10       33      23      30
DB5          31     12       32      11      31
DB6          32     14       31      12      32
DB7          33     16       30      13      33
DBP(par)     34     18       29      20      34

ATN          41     32      n/c      17      41
BSY          43     36        8       6      43
ACK          44     38        7       5      44
RST/RES      45     40        6       4      45
MSG/MES      46     42        5       2      46
SEL          47     44        4      19      47
C/D          48     46        3      15      48
REQ          49     48        2       1      49
I/O          50     50        1       3      50

GND       1-11       *     11-28  7,9,14   1-12
GND       15-25,  20,22     10**   16,18,  14-25
GND       35,36,  30,34              24    35-37,
GND       40,42,                          39,40,42

RESERVED  12,14,   23,27
RESERVED  37,39

OPEN         13      25     9,10**          13

TRM PWR      38      26     n/c      25     38


NOTE: 

Cables with the same connectors on both ends are wired pin for pin. Cables with different connectors on its ends are wired according to the above chart.

  * All ODD pins except 23, 25, 27.
** Pin 10 is open on PC2 Adapters, but is tied to ground on the PCI, PC3, and PC4 adapters.

NCR 86C01 Snippets complete thread "An MCA ESP driver" HERE 

Michael Necasek pulled this out while traveling...

" OK, here's the goods I promised.  The NCR 86C01 is an MCA interface chip that handles enabling/disabling IRQ, DMA interfacing, I/O port selection and other fun stuff.  It takes up 16 addresses, and the chip it is connected to gets the following 16.  Registers are as follows:

Offsets 0-1 : Card ID

Offset    2 : Mode enable register --
             Bit    7 : Data Word width (1 = 16, 0 = 8)
             Bit    6 : IRQ enable (1 = enabled)
             Bits 5,4 : IRQ select
                        0  0 : IRQ 3
                        0  1 : IRQ 5
                        1  0 : IRQ 7
                        1  1 : IRQ 9
             Bits 3-1 : Base Address
                        0  0  0 : <disabled>
                        0  0  1 : 0x0240
                        0  1  0 : 0x0340
                        0  1  1 : 0x0400
                        1  0  0 : 0x0420
                        1  0  1 : 0x3240
                        1  1  0 : 0x8240
                        1  1  1 : 0xA240
                Bit    0 : Card enable (1 = enabled)

Offset    3 : DMA control register --
             Bit    7 : DMA enable (1 = enabled)
             Bits 6,5 : Preemt Count Select (transfers to complete after
                       86C01 has been preempted on MCA bus)
                        0  0 : 0
                        0  1 : 1
                        1  0 : 3
                        1  1 : 7
 (all these wacky numbers; I'm sure there's a reason somewhere)
             Bit    4 : Fairness enable (1 = fair bus priority)
             Bits 3-0 : Arbitration level (0-15 consecutive)

 Offset    4 : General purpose register
              Bits 7-3 : User definable (here, 7,6 are SCSI ID)
              Bits 2-0 : reserved

 Offset   10 : DMA decode register (used for I/O based DMA; can do PIO through this port)

Offset   12 : Status
              Bits 7-2 : reserved
              Bit    1 : DMA pending (1 = pending)
              Bit    0 : IRQ pending (0 = pending)

  Exciting, huh?"

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