PCjs Machines
Home of the original IBM PC emulator for browsers.
COMPAQ DeskPro 386
DeskPro 386 configurations currently include:
All configurations currently use IBM display adapters. Configurations with COMPAQ Monochrome Graphics, COMPAQ Enhanced Graphics, and COMPAQ VGA will eventually be added as well.
COMPAQ DeskPro 386/25 Technical Reference Guide
Originally, all we had was the first volume of DeskPro 386/25 Technical Reference Guide. Its table of contents gave us a taste of what was in Volume II:
- Chapter 5 KEYBOARD
- Chapter 6 POWER SUPPLY
- Chapter 7 MULTIPURPOSE FIXED DISK DRIVE CONTROLLER BOARDS
- Chapter 8 DISKETTE DRIVES
- Chapter 9 FIXED DISK DRIVE SYSTEMS
- Chapter 10 FIXED DISK DRIVE BACKUP SYSTEMS
- Chapter 11 VIDEO DISPLAY CONTROLLER BOARDS
- Chapter 12 MONITORS
- Chapter 13 ASYNCHRONOUS COMMUNICATIONS/PARALLEL PRINTER BOARD
- Chapter 14 COMPAQ 300-/600-MEGABYTE FIXED DISK DRIVE EXPANSION UNIT
- Appendix A INTERNATIONAL KEYBOARDS
- Appendix B ERROR MESSAGES
Fortunately, PCjs was later able to acquire both volumes of the original DeskPro 386/16 Technical Reference, so we have much more than a “taste” now.
NOTE: As the page on COMPAQ DeskPro 386 ROMs explains, 5 COMPAQ engineers had their initials “engraved” in the original DeskPro 386 ROM. In June 2018, I was fortunate enough to meet 4 of them, and they were all kind enough to sign my copy of the DeskPro 386 Technical Reference Guide. This “signature page”, shown below, has since been added to the PDF above.
COMPAQ DeskPro 386 Reference Highlights
Fixed Disk Drive Parameter Table Values
The first table comes from pages 4-119 and 4-120 of the DeskPro 386/16 Technical Reference Guide (Volume I), dated September 1986 (First Edition). These are the values used by PCjs in driveinfo.js for COMPAQ machines.
Note that COMPAQ calculated raw capacity by multiplying cylinders, heads, and sectors per track by 512 bytes per sector and then dividing the total by 1,000,000, a common industry practice that “inflated” disk capacity. PCjs considers 1 megabyte (Mb) to be 1,048,576 bytes (1024 x 1024), so any capacity calculations that PCjs reports will be smaller than the values shown below.
Landing
Pre-comp. Zone
Drive Max. Cylinder Cylinder Sectors/ Capacity Same as
Type Cylinders Heads (note 1) (note 2) Track (MB) IBM PC AT
---------------------------------------------------------------------------------
1 306 4 128 305 17 10.65 Yes
2 615 4 128 638 17 21.41 Yes
3 615 6 128 615 17 32.12 Yes
4 1024 8 512 1023 17 71.30
5 940 6 512 939 17 49.09 Yes
6 697 5 128 696 17 30.33
7 462 8 256 511 17 32.17 Yes
8 925 5 128 924 17 40.26
9 900 15 No 899 17 117.50 Yes
10 980 5 No 980 17 42.65
11 925 7 128 924 17 56.36
12 925 9 128 924 17 72.46
13 612 8 256 611 17 42.61
14 980 4 128 980 17 34.12
15 0 0 0 0 0 0
16 612 4 0 612 17 21.31 Yes
17 980 5 128 980 17 42.65
18 966 6 128 966 17 50.45
19 1023 8 No 1023 17 71.23
20 733 5 256 732 17 31.90 Yes
21 733 7 256 732 17 44.66 Yes
22 768 6 No 768 17 40.11
23 771 6 No 771 17 20.16
24 966 14 No 966 17 117.71
25 966 16 No 966 17 134.53
26 1023 14 No 1023 17 124.66
27 966 10 No 966 17 84.08
28 771 3 No 771 17 20.11
29 578 4 No 578 17 20.09
30 615 4 128 615 25 31.49
31 615 8 128 615 25 62.98
32 966 3 No 966 34 50.45
33 966 5 No 966 34 84.08
34 966 7 No 966 34 117.71
35 966 8 No 966 34 134.53
36 966 9 No 966 34 151.35
37 966 5 No 966 34 84.08
38 1023 9 No 1023 33 155.56
39 1023 11 No 1023 33 190.13
40 1023 13 No 1023 33 224.70
41 1023 15 No 1023 33 259.27
42 1023 16 No 1023 34 284.93
43 756 4 No 756 26 40.26
44 756 2 No 756 26 20.13
45 768 4 No 768 26 40.89
46 768 2 No 768 26 20.45
47 966 5 128 966 25 61.82
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The next table comes from pages 4-189 and 4-190 of the DeskPro 386/25 Technical Reference Guide (Volume I), dated August 1988 (First Edition). Note that the table is largely identical to the earlier version above, except for drive types marked by *. There are also 3 entries marked by ** that warrant further investigation, because they specify more than 1024 cylinders, which the INT 13H BIOS interface at that time did not support.
Landing
Pre-comp. Zone
Drive Max. Cylinder Cylinder Sectors/ Capacity Same as
Type Cylinders Heads (note 1) (note 2) Track (MB) IBM PC AT
-----------------------------------------------------------------------------------------
1 (note 3) 306 4 128 305 17 10.65 Yes
2 (note 3) 615 4 128 638 17 21.41 Yes
3 615 6 128 615 17 32.12 Yes
4 1024 8 512 1023 17 71.30
5 940 6 512 939 17 49.09 Yes
6 (note 3) 697 5 128 696 17 30.33
7 462 8 256 511 17 32.17 Yes
8 925 5 128 924 17 40.26
9 900 15 -1 899 17 117.50 Yes
10 980 5 -1 980 17 42.65
11 925 7 128 924 17 56.36
12 (note 3) 925 9 128 924 17 72.46
13 612 8 256 611 17 42.61
14 980 4 128 980 17 34.12
15 Reserved - Not for use by end-users
16 612 4 0 612 17 21.31 Yes
17 980 5 128 980 17 42.65
18 966 6 128 966 17 50.45
19 1023 8 -1 1023 17 71.23
20 733 5 256 732 17 31.90 Yes
21 733 7 256 732 17 44.66 Yes
22* 524 4 -1 524 40 42.93
23* 924 8 -1 924 17 64.34
24 966 14 -1 966 17 117.71
25 (note 3) 966 16 -1 966 17 134.53
26 1023 14 -1 1023 17 124.66
27* 832 6 -1 832 33 84.34
28** 1222 15 -1 1222 34 319.09
29** 1240 7 -1 1240 34 151.10
30 615 4 128 615 25 31.49
31 615 8 128 615 25 62.98
32* 905 9 128 905 25 104.26
33* (note 3) 832 8 -1 832 33 112.46
34 966 7 -1 966 34 117.71
35 (note 3) 966 8 -1 966 34 134.53
36 966 9 -1 966 34 151.35
37 966 5 -1 966 34 84.08
38* (note 3) 611 16 -1 611 63 315.33
39 1023 11 -1 1023 33 190.13
40* 1023 15 -1 1023 34 267.13
41** 1630 15 -1 1630 52 650.96
42* 1023 16 -1 1023 63 527.97
43* 805 4 -1 805 26 42.86
44* 805 2 -1 805 26 21.43
45* (note 3) 748 8 -1 748 33 101.11
46* 748 6 -1 748 33 75.83
47 (note 3) 966 5 128 966 25 61.82
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NOTES: 1. A value of -1 means that no write precompensation is used.
2. These values are not used by the COMPAQ DESKPRO 386/25 system, which
automatically retracts and locks the heads in a non-data landing zone
at power-down.
3. Drive types supported by Compaq.
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Documents
(Volume I, Sep 1986)
(Volume II, Sep 1986)
(Volume 1, Oct 1987)
(Volume 2, Oct 1987)
(Volume I, Aug 1988)
(Volume II, Aug 1988)