SCSI-2 Differential F/W

"Corvette Turbo"

@8EFC.ADF IBM PS/2 Fast/Wide SCSI Adapter (Uses same ADF as SE F/W)
C8EFC.ADF Init file for @8EFC.ADF

rev71upd.exe SCSI-2 Fast/Wide Adapter Firmware Upgrade .71
corv77.exe SCSI-2 Fast/Wide Adapter Firmware Upgrade .77
corvC9.exe SCSI-2 F/W Enhanced Fast/Wide Firmware Upgrade FRU 93H7896 & 52G3380
ibm2.exe F/W and OS/2 2.1 Fix '94 (ibm2scsi.add and ibm2m57.add)
scsi2fw.exe SCSI-2 F/W Support Diskette v2.0
scsi2fw.txt Readme for scsi2fw.exe

SCSIFIX.ZIP A utility to alter the number of sectors for a SCSI drive and convert them to a 3.94GB drive. (thx Bob Eager!)

194-145 SCSI-2 F/W Adapter/A, SCSI-2 Differential F/W Adapter/A

Adapter Microcode Protection during Download (TDB) (old)

Possible MCA Interface Chip Problems

Differential SCSI-2 Fast/Wide Adapter
   Rework on 11H7660 Front
   Rework on 11H7660 Back
Enhanced Differential SCSI Fast/Wide Adapter
Jumpers on the Fast/Wide
68 pin Internal Connector
Drive connector
SCSI device and adapter configuration flexibility
SCSI Device Order
Maximum SCSI Devices Supported
Fast POST Consequences
ADF Sections
ESDI Requirements

Differential SCSI Fast/Wide Adapter "Corvette Turbo"

FRU P/N 11H3599 (no workee) / 11H7660 (workee) (RS/6000 4-6)

J1 50 pin SE SCSI connector
J2 Factory use
J3 C-68 DFW SCSI connector
J5 Leave open. Not used.
J6 Boot Enable
J7 FW SE SCSI connector
RN1,2,3 Used for RS6K stuff
TR1 PTC resistor for internal bus
TR2 PTC resistor for external bus
U1 61G3929, SCSI BIOS, Odd
U2 61G3930, SCSI BIOS, Even
U8,9 Sony CXK581000AM-70LL
U10 AMD N80C186-20
U11 40.0000 MHz osc
U12 82G2645 Int SE SCSI ctrlr
U13 61G2323 MCA Bus interface
U14 52G9707 Ext Diff SCSI ctrlr
U15 empty (unused even in RS6K)

RN1,2,3 Removed on RS/6000 systems when a high-reliability configuration is used (one of them there "Y" arrangements illegal to normal SCSI users).

What is With the Yellow Termpacks?
Differential SCSI uses a standard passive resistor termination. This terminator remains unchanged from the original SCSI-1 standard to the proposed SCSI-3 physical layer. So you might be confused why a newer SCSI adapter uses the older yellow termpacks like the three can Spock.

  The SCSI-2 Differential Fast/Wide Adapter/A supports an internal single-ended and an external differential SCSI bus. 

FRU 11H3599
   To date, all attempts to get this RS/6000 adapter to work in a PS/2 have failed. Although the chipset is the same as on the Fast/Wide, the rev .71 flash update does not recognize a F/W chipset.

FRU 11H7600  
  This FRU with a PLCC socket WILL work with no special poodle faking. User "No Deal" has posted images of the Set Configuration and Set and View SCSI Devices screens.

How Many is Enough?

Tim Clarke uttered this after a pint of warm beer:
   All **IBM** SCSI CBIOS-flavour (i.e. *not* FD MCS700 OEM) will share IRQ14 and you only need one BIOS ROM enabled to drive multiple adapters. So, for example you *should* be able install (in the same slot-type, please) IBM F+W SCSI-2 "Corvette", IBM SCSI w/cache ("Spock") and IBM SCSI w/o cache ("Tribble") in the same PS/2. No naughties like AHA1640, Storage Dimensions unless you disable their BIOS ROMs and assign a different IRQ.

OS Limits

Not all Microsoft products support multiple IBM SCSI adapters gracefully. W9x cannot handle shared IRQs and will drop into MS-DOS compatibility mode. Win NT, OS/2, Linux and other UNIX systems can handle shared interrupts.

J7 Pinout
IBM's patent info/Tech Discovery Bulletins, TDB identifies the Burn/Alive/TXD/RXD as being used to flash certain components. Basically, factory use only.

Fast/Wide in 8590/8585
   If you don't have a Type 4 complex on a 95A (dual serial/dual parallel), you may not be able to use some features of the Fast/Wide, most notably Internal/External Bus Mode. You need to run SCSI2FW.EXE to update the system partition.

FRU 11H7660
   To my surprise, the 11H7660 configures fine, flashes to .71, and works like a normal F/W.

Front 11H7660 DFW Rework


Rear 11H7660 DFW Rework

Rework A comes off the fourth MCA contact.
Rework B comes off the solder pad marked with a V.
Rework C comes off the third pin on the upper left of U23.
Rework D comes off the second pin of U23.

Jim Shorney rains on our parade- he warns that foil cuts may have been made in addition to the rework wires.

Enhanced Differential SCSI Fast/Wide Adapter

FRU P/N 52G3380 (workee) (RS/6000 4-C)

J1 FW SE SCSI connector
J2 50 pin SE SCSI connector
J3 C-68 DFW SCSI connector
J5 Leave open. Not used.
J6 Boot Enable
J7 Factory use
RN1,2,3 Used for RS6K stuff
TR1 PTC resistor for internal bus
TR2 PTC resistor for external bus
U1 88G1094, SCSI BIOS, Odd
U2 88G1095, SCSI BIOS, Even
U4 82G2645 Int SE SCSI ctrlr
U5,18 NS DS36954
U9,10 Sony CXK581000AM-70LL
U11 AMD AM186 EM-40VC
U12 88G1092
U13 88G1093
U16 61G2323 MCA Bus interface
U17 52G9707 Ext Diff SCSI ctrlr
Y1 40.0000 MHz osc

Rear of Enhanced DFW

U19,21,22,26,27 DS36954
U20,25 89F7000 Term Network, SE

DS36954 Quad Differential Bus Transceiver
AN-904 Application Note 904 An Introduction to the Differential SCSI Interface

Why Five DS36954?

Remember, this adapter was used by AIX, and supports a high-reliability configuration

"Five devices can implement a complete SCSI initiator or target interface. Three transceivers in a package are pinned out for data bus connections. The fourth transceiver, with the flexibility provided by its individual enables, can serve as a control bus transceiver."

If you look at the further two DS36954 on the front (by the yellow termpacks), it seems we would need five complete DS36594 plus one gate from a sixth DS36594 for 16 bit SCSI, and the rest of the gates (three from the sixth and four from the seventh) are used for control.

89F7000 Term Network, SE

These are the same parts used on the Corvette for automatic termination of the internal Single Ended ports.

The SCSI-2 Differential Fast/Wide Adapter/A is a dual-ported, fast and wide (two bytes wide) SCSI Micro Channel adapter that provides synchronous SCSI bus data rates of up to 20MBps. The internal SE port is capable of addressing up to seven SE SCSI devices and the differential external port is capable of addressing up to seven differential SCSI devices, providing a maximum of 14 devices per adapter. The number of physical devices attached to each port is limited by SCSI bus cabling restrictions. The external differential port can support a total cable length of 25 meters (82 feet).

Additional system, subsystem and high-availability connections are also available with the differential system-to-system and Y-cable features.

Corvette vs. Enhanced Corvette Turbo

William R. Walsh wrote:
   Quick testing in the Server 95A upgraded to P180MMX shows a bit of a speed improvement over the standard issue Corvette. Using a Seagate 10,000 RPM SCA hard disk and UZ's "no-LED" driver, I got:

Max 11.5MBP/S
Min 10.6MBP/S
Avg 11.1MBP/S
Enhanced Corvette Turbo:
Max 13.7MBP/S
Min 13.0MBP/S
Avg 13.9MBP/S

The Enhanced Corvette Turbo shows a CPU utilization of 10.4% compared to the Corvette's 10.1%. Tests were run using the Simpli Software HDTach tool, which was used before during SPOCK-206 NT driver testing.

PTC Function

There is one PTC for the internal SCSI bus and another for the external bus. The PTC protects the SCSI bus from high currents due to shorts on the cable, terminator, or device. It is highly unlikely that the PTC resistor can be tripped by a defective adapter.

A fault (short circuit) causes an increase in PTC resistance and temperature. The increase in resistance causes the PTC resistor to halt current flow. The PTC resistor returns to a low resistance and low temperature state when the fault is removed from the SCSI bus or when the system is powered off. Wait 5 minutes for the PTC resistor to fully cool, then reset.

Bourns MF-SM Series MF-SM150.

PLCC Socket on Fast/Wide
   The PLCC Socket U7 was possibly to provide a RS/6000 BIOS, and the jumper J5 might have been to enable it. Documentation for the RS/6000 says that PLCC socket is unused. The related  4-4 [11H4779] SCSI-2 SE High Performance Internal/External I/O Controller has a chip (FRU 52G7507) in the PLCC socket. The 4-4 is the only F/W related SCSI adapter to have the PLCC chip installed..

Jumpers on Fast/Wide
   The results of shorting the jumpers ranged from no difference, slight performance hit (%10 overhead increase) or a system-halting error. Leave them off. RS6000 documentation says the jumpers are to be left open.

   J5 grounds out pin 33 on the internal SCSI controller 82G2645. Purpose unknown.
   J6 grounds out pin 1 of U1 and U2. Marked "Boot Block Enable"

68 pin Internal Connector on D F/W SCSI Adapter
  This is a "mini-Centronics"  or a Vesa Media Channel plug. The ANSI moniker for it is a "P" plug. Also seems to be used for SCA drives... Hmm...

AMP (and Tyco)  # 1-557089-2
Looks like THIS or if you want the page go HERE

Newark Electronics 97F8813
   CHAMP. 0.050 I Series Interface Connectors For VMC Applications: 68-Position 

  Designed for use with 30 AWG solid conductors on .064mm (.025") centers.  look HERE

Molex 71660i  Molex part 15-92-3068 1.27mm (.050") Pitch
  EBBI™ 50D - Receptacle, Vertical, IDT 71660i Looks like THIS
   Terminates to 30 AWG solid or stranded .025" ribbon or laminated discrete wire cable 

Drive connector
The 68 pin crimp-on device connector. Dalco 59611  $4.25

SCSI device and adapter configuration flexibility 
   Systems with the enhanced SCSI device and adapter support allow up to 8 IBM PS/2 SCSI adapters of any type to be installed in a single system. The maximum number of SCSI devices which many be configured in these newer systems has also been increased from 60 to 120.  However, other factors, for example, the type of devices (optical, etc.), cooling requirements, or power consumption of the devices may limit the number for a particular system. 

SCSI Device Order
   SCSI device logical ordering and hard drive letter assignment (e.g. C:, D:) sequence is determined by the SCSI adapter slot numbers, internal or external SCSI bus connection, and SCSI ID of the connected devices.

   Adapters are scanned for SCSI devices beginning with the SCSI adapter in the lowest numbered slot.  Devices connected to the same adapter are logically ordered according to device SCSI IDs in order from 7 to 0 and then from 15 to 8 according to the priority scheme defined by the SCSI standard.  Devices connected to a SCSI-2 Fast/Wide adapter's internal bus connector are ordered logically before devices connected to the external bus of the same adapter. 

Maximum SCSI Devices Supported
   Wide SCSI devices support 16 possible SCSI ID values.  The adapter uses one these values; therefore, the SCSI-2 Fast/Wide adapter can connect up to 15 fast and wide devices internally or externally in any combination using the remaining ID values.  Narrow SCSI devices support 8 possible SCSI ID values; therefore, up to 7 narrow SCSI devices can be connected to the internal or external SCSI busses in any combination using the remaining ID values.  Wide and narrow devices may be mixed on the same internal/external bus by using the proper combinations of SCSI bus cables, terminators, and/or SCSI connector converter adapters.

   Note: Use of a 8 bit (Narrow) cable forces the controller to default to only 7 devices supported on that port, even if all devices on that cable are Wide. 

Fast POST Consequences
   Some newer systems also provide a FAST POST option which may be selected from the system configuration menu or from the IBM logo screen.  When this option is selected, the system will not check for the presence of newly added SCSI devices unless F1 is also pressed while the IBM logo is displayed.  Newly added SCSI devices will not be configured nor will an error occur if the fast post option is chosen as the default. To access the system configuration program, press F1 while the IBM logo screen is displayed to configure the new SCSI  device(s) initially. 

ADF Sections @8EFC.adf 4/10/95

I/O Address 
   I/O address for the adapter. Each adapter must have a unique address range.
    <3540-3547>, 3548-354F, 3550-3557, 3558-355F, 3560-3567, 3568-356F, 3570-3577, 3578-357F, 3578-357F 

DMA Arbitration Level
   Arbitration level used by the adapter to transfer data.
   <C>, D, E, 8, 9, A, B, 1, 3, 5, 6, 7 

SCSI Adapter Address (ID)
   SCSI ID of the adapter. Usually ID7, unless you have specific requirements.
   Adapter IDs available are: <7>, 6, 5, 4, 3, 2, 1, 0

Move Mode Support
   Enable or Disable Micro Channel Subsystem Control Block Move Mode This is the second mode of SCBA (first is locate mode) which permits the system processor to move the subsystem control blocks to the adapters directly.
   <Enabled> or Disabled 

Wait State Support
   Enable or Disable Bus Master wait states. If the target expansion card is an older card, it may not be able to process commands or data from the busmaster fast enough, and when queried by the busmaster, it replies with "not ready". By inserting a wait state, the slower card has more time to signal "ready". Enabling wait states can slow your busmaster down.
   <Disabled> or Enabled 

Data Parity Exception Handling
   This Adapter can generate and detect data parity on Micro Channel. Data parity must be supported on both ends of an across-the-bus transmission in order for this error detection process to be effective. A data parity enable (-DAPAREN) bus line to the system and other expansion boards is enabled when data parity is being used. If the System does not support Data Parity Exception Handling, this feature will always be disabled.
   <Enabled> or Disabled 

Selected Feedback Return Exception
   When enabled, the busmaster monitors the selected feedback return and card-selected feedback buslines. The return line tells the master that it's target expansion board is responding properly to being addressed for a read or write operation. If the bus master does not receive this signal (and SFR has been enabled) it may mean that the expansion board is not operating properly or that the signals themselves are not properly traveling across the expansion bus. This error causes the master to immediately halt the transfer in progress and notify the host system of the error using an interrupt. Note: The SFR must be ignored for PC compatibility. If the System doesn't support the Selected Feedback Return feature, it will always be ignored.
   <Enabled> or Ignored 

100 ns Streaming Data Transfer Support
   This provides better performance. It will always be disabled if the system doesn't support it.
   <Enabled> or Disabled 

Target Mode
   Target mode should be disabled only if this system is sharing SCSI devices with another system and there are more than 15 devices to be shared.  Only 15 devices can be configured on each adapter.

When target mode is enabled, this adapter appears as a processor device on the other system and unless you have specialized software that can communicate between the two systems through these processor devices (peer-to-peer communication), there is no advantage in having target mode enabled.

When target mode is disabled, this adapter does not appear as a device to the other system, and one more device can be shared by the two systems.  If your system is not sharing any SCSI devices with another system on this adapter, it does not matter whether you enable or disable target mode.
   <Enabled> or Disabled 

SCSI Disconnect
   Disconnect is a SCSI-bus procedure in which a device logically stops communicating with the adapter during certain operations and then reestablishes communication with the adapter when the operation is complete.  Disconnect should not be confused with the 'Presence Error Reporting' option for a device in 'Set and view SCSI device configuration.'  If you are using an operating system that is single-threaded and issues commands to only one device at a time (such as DOS or Win95), disabling SCSI disconnect might result in a slight performance improvement.  If your operating system is multi-threaded (such as OS/2), disabling SCSI disconnect will degrade the performance of the SCSI subsystem.
   <Enabled> or Disabled

Fast SCSI - External
  If Fast SCSI devices are attached externally, enabling Fast SCSI improves performance.
  - One external SCSI device enclosure model 3511.
  - Up to three external SCSI device enclosures model 3510.
  - Any external configuration where SCSI cable length isn't > 3 meters.
   <Disabled> or Enabled 

Wide SCSI messages - External
   'Enabled' unless Wide SCSI devices are attached through a narrow external interface cable.
   <Enabled> or Disabled 

Wide SCSI messages - Internal
   'Enabled' unless Wide SCSI devices are attached through a narrow internal interface cable.
   <Enabled> or Disabled 

Internal/External Bus Mode
   'Separate', SCSI devices on external SCSI bus connector can have the same SCSI ID setting as other SCSI devices connected to  internal SCSI bus connector on the same adapter.
    'Combined', all devices connected to this adapter must have unique SCSI ID settings regardless of which SCSI bus connector is used to attach the devices.  Default is 'Separate' unless you are using an operating system device driver that does not support independent operation of the internal and external SCSI busses on the adapter.
    <Separate> or Combined

Note: SCO Unix and Banyan Vines can not recognize devices configured on the SCSI-2 F/W Adapter (DFW as well), when in a 90 /95 level 3 BIOS or higher.  This is due to the the internal and external ports beinge separated.  A special version of the SCSI-2 F/W Adapter's ADF  (@8EFC.ADF) file is available to allow the busses to be set to a COMBINED state, which overcomes this problem.

Note: I don't know what version this is for, nor do I know if later versions of SCO Unix and Banyan Vines fixed this issue. The last version of the F/W ADF has "COMBINED" as a choice.

System Determined
ROM Address Range
   Address of the 32K block of memory assigned to the adapter. Only one SCSI Adapter will have the ROM assigned, and any other SCSI Adapter installed will share that address range. 

ESDI Requirements
   If the ESDI adapter is also installed, then the address of the SCSI adapter must be greater than the ESDI adapter address.

ESDI Requirements
   If the ESDI adapter is also installed, then the address of the SCSI adapter must be greater than the ESDI adapter address. 

Content created and/or collected by:
Louis Ohland, Peter Wendt, David Beem, William Walsh, Tatsuo Sunagawa, Jim Shorney, Tim Clarke, Kevin Bowling, Tomáš Slavotínek, and many others.

Ardent Tool of Capitalism - MAD Edition! is maintained by Tomáš Slavotínek.
Last update: 25 Nov 2022 - Changelog | Legal Info & Contact