BusLogic BT-646

@0708.ADF BusLogic BT-646 S/D SDC3211F FAST SCSI
@0709.ADF Storage Dimensions SDC3211F FAST SCSI (Same board, different ADF!)

BT-646 ADF

BT-646 User's Guide
646s-336.zip Firmware 3.36 and SCSI BIOS 4.70 Requires EPROM burner!
   Original used ST Microelectronics M27C256B -12F1

SDC3211F Firmware BIN file, 3.38 ODD [U5]
SDC3211F Firmware BIN file, 3.38 EVEN [U6]
   "27128" silk screened inside socket, but it used Macronix MX27C256PC-12 [28 pin DIP]

Looks like they diddled with it, 0000-03FF is all 0s, 0400-07FF are data.
BT-646 Fast Micro Channel Host Adapter Technical Reference P/N 3002113

MultiMaster Device Drivers

Mylex was bought by LSI Logic. Downloads (for now) are HERE

BT-646 / SDC3211F
LED Operation
   BIOS Revisions
   Access BusLogic Firmware Menus
Drive Power Connector
ADF Sections 

BT-646 S/D and SDC3211F 32-Bit Fast SCSI-2

D2 1N5820
D3 1N5817
F1 Littlefuse MSF 125v 1.6A
J1 50 pin header
J2 HPDB50 port
J4 Power
JS1-55 0 Ohm shunts (-S only!)
RP2,3 CTS 4610X-1-101 (-S only!)
RP4,5 10X-1-221 (-D only!)
RP6-13  4610X-2-151 or -331 (-D only!)
U1,2 KM6865BJ-20
U5 Firmware high byte
U6 Firmware low byte
U15 BIOS high byte
U16 BIOS low byte
U17 AMD N80C186-20 (MPU)
U22 BusLogic 80C20 (DMA Busmaster)
U27 40.0000 MHz osc
U28 SCSI IF Ctrlr
U33 DM7407M
U34 74F04
U35 7408D (-D) F08 XAC250 (-S)
U36-38 DM74LS08M (-D only!)
U39-44 TI 751768 (-D only!)
U45-47 DS36954AV (-D only!)
VR1 LT1086CT 2.85 (-S only!)

U28 may be an Emulex 2400150 or a  QLogic FAS236FAS236 datasheet

BT-646S single-ended termination - has RP2 and RP3 only.
RP2, R3 - 10-pin 100 ohm SIPs containing 9 bused 100 ohm resistors (CTS 4610X-1-101) 

BT-646D differential termination - has RP6-RP13
RP6,8,10,12 are 10-pin SIPs with 5 isolated 150 ohm resistors (Bourns 4610X-2-151)
RP7,9,11,13 are 10-pin SIPs with 9 bused 330 ohm resistors. (Bourns 4610X-1-331) 

DS36954AV The DS36954 is a low power, quad EIA-485 differential bus transceiver especially suited for high speed, parallel, multipoint, I/O bus applications. 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.Datasheet

Primary Controller in Non-IML System
   Enable the BIOS. Set your boot drive to ID0 or the BT-64x will not be able to boot from it. Also, you should set the boot drive to "autostart" so it spins up as soon as the system is turned on. I had a 0662 set to ID0, but the BT-646 complained about Target 0, Lun 0 not being detected, but then showed the 0662 at ID0, then the CD at 6,0. After jumpering the 0662 to autostart, everything was fine.

BT-646S/D SCSI Adapter for MicroChannel Systems
  32-bit bus master DMA transfers of up to 40MB/second across the MC bus, up to 10 MB/sec synchronous and up to 7 MB/set asynchronous SCSI data transfers. Support for up to seven SCSI devices, hard drives with up to 8GB capacity each. Enhanced SCSI-2 features: scatter-gather, disconnect-reconnect, and command-tag queuing

BT-646x Host Interface Microprocessor
   A 20MHz Intel 80186 16-bit MPU is used to supply the speed for low command overhead. This MPU coordinates all activity on the BT-646S/D under the direction of the board’s firmware, including initialization, command decoding, interrupt generation, and control of the data flow among the board’s components.

Accessing BusLogic Firmware Menus

Boot from a DOS disk (which should include debug.exe)

-g=dc00:6 (BIOS Base Address:Offset Number) DC00 is the default BIOS address

A screen will appear and prompt you to proceed. You can use these menus to SCSI Format (Low-Level Format) a disk, or perform other SCSI functions.

Buslogic Tips

  • Ensure that all Buslogic Host Adapters in a Multiple Host environment are at the same Firmware/BIOS level. This is important if you are replacing or adding new Host Adapters in an existing system.
  • Check that C43, a surface mount capacitor on the reverse side of the PIB is removed. This was to cure loss of video on warm-boot. This change has been incorporated into the Buslogic Boards supplied with new Systems at Firmware level 3.37/4.73.
  • Prior to Firmware level 3.37/4.73 you must ensure that you do not have a Tape or CD-ROM device set at ID=1 on the Primary Host Adapter. It interferes with the Buslogic POST testing as it expects to see a Hard Disk only.
  • 3430 System BIOS 1.07 or greater is required for use with BusLogic cards.
  • DOS will only see two hard disks attached to the Buslogic Subsystem, at ID=0 and ID=1, you must use DOS device drivers to see any more. Refer to the RAID section of this manual for more info.
  • During Buslogic Initialization the screen shows which SCSI devices are responding on the Primary Host Adapter only.
  • You can use DOS Debug command to scan the SCSI Bus for devices.
  • Under NT 4.0, the MS default Buslogic driver will not allow sharing of interrupts. To work around this, use the driver from NT 3.5x or a copy of the driver from BusLogic/Mylex.

Buslogic Firmware History

There are 4 EPROMS on the Buslogic PIB's. 2 are the PIB's Firmware, U5 & U6. and two are BIOS extensions, U15 & U16.

Current F/W levels (Note the version without a suffix is the latest, i.e. 3.36c precedes 3.36)


U5 & U6    U15 & U16    NT USE?
-------    ---------    --------
3.31        4.50        Do Not Use
3.36c       4.70        OK *1 *2
3.36        4.71A       OK *2
3.36        4.73        OK *2
3.37f       4.73        OK
3.37        4.73        OK
3.38        4.73        OK (needed for Differential w NCR RAID)
3.39        4.73        OK (Required for NT 4.0)

Ensure all Buslogic HBAs in Multiple Host environment use same Firmware/BIOS level.

*1 - Does not issue spin-up command, so jumper Hard Disks to enable spin-up at power on.
*2 - SCSI bug that causes periodic SCSI bus timeouts, and can be a problem for large NT systems. If you have these versions, check your Event Log for SCSI errors to determine if you need to upgrade. These versions will also give errors if Tape and CD-ROM devices are at ID=1 on the primary controller.

Subsequent releases of firmware since 3.37f/4.73 correct various minor SCSI matters, but are not system threatening.

LED Operation
   When power is first applied to the BT-640A, an on-board diagnostic routine is run to verify that the major functional components of the board are operating correctly. The bus master chip, the SCSI controller chip, the firmware PROM, the local RAM and internal data buses are tested. Results of the tests are indicated by an LED on the board.
   The LED will first turn on when power is applied. If the diagnostics find no malfunctions, the LED will then go off. In normal operation, the LED will be illuminated when command or SCSI bus activity occurs on the board. If an error is detected by the diagnostics, the LED will repeatedly flash a specific number of times, with a long pause between flashes, to indicate the board function which failed. This will continue until the board is powered down or reset. Failure interpretation from the number of flashes is as follows: 
640A-646S/D Failure 
Always On
Not operating/missing terminator
Firmware ROM checksum failure
Local RAM test failure
SCSI controller / interface failure
Internal data bus failure
Internal address bus failure
Bus master chip failure
SCSI drive type mismatch*
Fuse Blown.

*This error is when single-ended SCSI drives are connected to the differential SCSI bus.

Disk Drive Power Connector
   A 4-pin disk drive power connector (J4) is located at the top edge of the BT-64x board next to the SCSI connector Jl. This connector provides +12V and +5V power.
   Note: The BT-64x brings the 12 volt power supply to the 4-pin power connector (14) via three gold fingers on the edge connector. The power rating of the Micro Channel edge connector on the12 volt is one ampere per finger. Consequently, the maximum power allowed from the 12 volts (Pin 1 of J4) is three amperes. Because certain large SCSI drives may require more than three amperes when their motors are spinning up, BusLogic recommends that this connector not be connected to these large SCSI drives.
   Based on the power rating of the SCSI drives, if is recommended that this power connector not be daisy chained to multiple drives.

Term Power Fuse
   SDCxx11x and BT-64x use a Microlite Little Fuse that is 125v and 1.6A (Littel 27301.5 125V 1.5A or equivalent micro fuse). It is difficult to see that the fuse is blown so you will need to use a VOM to test for continuity. The fuse can blow if termination power settings are not correct on the SCSI devices or if you disconnect the SCSI cables while the card or SCSI devices have power. (Ed. Sure ain't kidding!)

Multitasking Operation
   For operating systems such as UNIX, NetWare, and OS/2, the mailbox protocol of the BT-64x provides true multitasking operation. Through the use of a mailbox structure, the BT-64x can support up to 255 tasks with minimum host processor intervention. Onboard firmware controls all of the SCSI activity that a task requires, including the Arbitration, Selection, Disconnection, Reconnection, and command completion status. This same mailbox protocol supports both initiator and target mode operation permitting high speed host-to-host communication and scatter-gather data transfers.

AdapterID 0709  BT-646 / SDC3211F 32-bit FAST SCSI Host Adapter
File @0709.ALL  Contains all of the options available to this adapter. 

I/O Port Address
  I/O Port of the host adapter
   <"330h" (io 0330h-0333h)>, 230h (0230-0233), 130h (0130-0133), 334h (0334-0337), 234h (0234-0237), 134h (0134-0137) 

Interrupt Request
   Interrupt channel used to report status
    <"IRQ-11">, 10, 15, 14, 9, 12 

Arbitration Level
   DMA channel used to transfer data
    <"Level 5">, 6, 7, 4, 3, 1, 0 

Adapter SCSI Bus ID
   SCSI ID of the host adapter
    <"Device ID 7">, 6, 5, 4, 3, 2, 1, 0 

BIOS Address
   Memory location of the host adapter's BIOS PROM. Note, if two SDC3211B are in the system one must have its BIOS PROM disabled.
   <"DC000h"  (dc00-dfff)>, Disable, D8000h (d800-dbff), D4000h (d400-d7ff), D0000h (d000-d3ff), CC000h (cc00-cfff), C8000h (c800-cbff), C4000h (c400-c7ff) 

SCSI Parity Checking
   The host adapter will check SCSI Parity if 'On'
     <"On">, Off 

Synchronous Negotiation
   Synchronous transfer on the SCSI bus will be initiated by the  host adapter if 'Enabled'
   <"Enabled">, Disabled 

; The function of this bit was changed. The data width function is detected by the host adapter and this switch was ignored.
; Slot Data Width
;    The adapter can be inserted into a 16 or 32 bit slot on the motherboard.  ;This option controls the data transfer size of 16 or 32 bits
;    <"16">, "32" 

Data Streaming
   Streaming data procedure transfers data blocks by using a single address followed by multiple 16 or 32-bit data transfers within a single streaming data cycle. If data streaming is enabled for a Micro Channel bus that supports streaming, the host adapter can achieve a maximum data transfer rate of 40 MBytes/sec on the Micro Channel bus.  If data streaming is disabled or the Micro Channel bus does not support streaming, the maximum data transfer rate is 20 MBytes/sec.
    <"Disable">, Enable 

Arbitration Fairness
   Bus Arbitration Fairness controls whether the host adapter implements the fairness algorithm after it is preempted from the Micro Channel
   <"Off">, On 

1Gbyte Translation See the following section for more details
   Change CHS per track  to support drive capacity > 1 GB
    <"On">, Off 

Disk > 1 GB and not SCO UNIX.
    In the DOS environment, INT 13 calls are routed through the BT-64xA/S/D’s ROM BIOS. This on-board BIOS intercepts host interrupt 13H calls and dispatches a command to the BT-64x for all host to SCSI disk accesses. When the >lGB option is turned on, the BT-64x BIOS can access up to 8 GBytes per disk. Otherwise, it can only access the first 1 GBytes even if the formatted disk capacity is greater than 1GByte. This 1GByte restriction does not apply to other operating systems, such as NetWare, UNIX, SC0 UNIX 3.2.4, or OS/2 if the operating system can boot without accessing > 1 GBytes. If the operating system’s bootable image resides below 1 GBytes then it can boot via Interrupt 13H. Once any of these operating systems are booted, the disk accesses are not routed through Interrupt 13H and the operating system can access the entire disk space even if the > 1 GB option is not turned on.  

   Under SC0 UNIX 3.2.2, the >lGB option must be turned off because the operating system itself has a 1 GByte limitation. Otherwise, disk images may be corrupted when the 1 GByte boundary is reached. For SC0 UNIX 3.2.4, the operating system does not impose the 1 GByte limit, and this option can be turned on or off accordingly. Consequently, the >lGByte support must be turned on under the following two conditions: (1) the combined space of all the DOS partitions exceeds lGByte, or (2) >lGByte disk accesses are required to boot the operating system. To enable the > 1 GB support, turn on this option. Note: If this option is changed, you must reformat the disk to avoid corrupting the existing file system.  

   {Ed. The >1GB translation scheme is incompatible with IBM SCSI controllers. After formatting a DPES-13080 1.08GB drive on a BT-646S (>1GB translation enabled), I was unable to access it after then attaching the drive to a Corvette. I had to reformat the drive with the Corvette.]

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Last update: 19 Nov 2021 - Changes & Credits | Legal Info & Contact