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Western Digital WD1002-27X Controller


There are six versions of the WD1002-27X Controller:

ROM BIOS I.D. Feature Description

(1) --- none ---- F000 no ROM BIOS or mounting bracket
(2) --- none ---- F007 no ROM BIOS w/ mounting bracket
(3) 62-000087-030 F019 ROM BIOS 0 (standard)
(4) 62-000088-030 F022 ROM BIOS 1 (26 to 17 sector)
(5) 62-000089-030 F016 ROM BIOS 2 (26 sector)
(6) 62-000094-032 F301 Auto-Configuration ROM BIOS


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WD-27X Disk Parameter Table (BIOS 62-000089-030)


C800:0041 D5 03 05 D6 03 D6 03-0B 07 FF 03 00 00 00 00 00
C800:0051 DB 03 07 DC 03 DC 03-0B 00 FF 03 00 00 00 00 00
C800:0061 64 02 04 65 02 65 02-0B 07 A7 03 00 00 00 00 00
C800:0071 67 02 04 68 02 68 02-0B 07 AC 03 00 00 00 00 00


RLL Table begins at C800:0041 and contains four Drive Types.


Type Cyl Heads ReadWrC PreComp ECC CCB Std Format

0 981 5 982 982 11 7 255 3 x
1 987 7 988 988 11 0 255 3 x
2 612 4 613 613 11 7 167 3 x
* 3 * 615 4 616 616 11 7 172 3 x


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WD1002-27X Step Rate Tables


The CCB Option Byte and onboard MicroProcessor determine Step Rate.


MPU 1015-14 CCB Step Rate
0 3000 usec
1 3000 usec
2 3000 usec
3 3000 usec
4 200 usec
5 70 usec
6 3000 usec
7 3000 usec

MPU 1015-24 CCB Step Rate
and MPU 1015A-24 0 3000 usec
1 45 usec
2 60 usec
3 18 usec
4 210 usec
5 75 usec
6 30 usec
7 18 usec

MPU 1015-25 CCB Step Rate
0 3100 usec
1 46.5 usec
2 22.5 usec
3 10.5 usec
4 202.5 usec
5 70.5 usec
6 38.5 usec
7 10.5 usec

MPU 1015E-08 CCB Step Rate
0 3300 usec
1 24 usec
2 24 usec
3 11 usec
4 24 usec
5 24 usec
6 24 usec
* 7 * 11 usec


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WD-27X Jumper Settings (BIOS 62-000089-030)


Drive Type: Device 0 Device 1
S1-1 S1-2 S1-3 S1-4 Jumpers for:
0 Close Close Close Close 981 Cyl 5 Heads
1 Open Close Open Close 987 Cyl 7 Heads
2 Close Open Close Open 612 Cyl 4 Heads
* 3 * Open Open Open Open 615 Cyl 4 Heads


S1-5 S1-6 Jumpers for:
Close Close RLL - 17 Sectors per Track (W9 ON )
* Open * Close * RLL - 26 Sectors per Track (W9 OFF)
Close Open RLL - 17 Sectors per Track (W9 OFF)
Open Open MFM - 17 Sectors per Track (W9 OFF)


S1-7 Jumper for:
Close IRQ 2 Select
* Open * IRQ 5 Select


S1-8 Jumper for:
Close AT Buss Mode
* Open * XT Buss Mode


* W3 * ON pins 1 & 2 Enable BIOS
W3 OFF pins 1 & 2 Disable BIOS

W4 ON pins 1 & 2 Device Address 0324H
* W4 * ON pins 2 & 3 Device Address 0320H

W6 ON pins 1 & 2 R.W.C. 9 - 16 Heads
* W6 * ON pins 2 & 3 R.W.C. 0 - 8 Heads

W8 ON pins 1 & 2 Secondary Controller
* W8 * ON pins 2 & 3 Primary Controller

W9 ON pins 1 & 2 Enable Firmware
* W9 * OFF pins 1 & 2 Disable Firmware


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WD-27X RLL Primary Format Procedure (BIOS 62-000089-030)


RLL Format begins at C800:0005 and requires two parameters:


A:\> DEBUG

-RAX ; AH = Drive 00 or 01 (Default = 00)
AX 0000 ; AL = Interleave 02 to 07 (Default = 04)
:0004 ; AX = 0004 Default
-G=C800:5


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