Compaq MSB900 - Manual (Page 32)

DIGITAL-LOGIC AG MSB900/L Detailed Technical Manual V1.0
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CMOS Map continued...
Location Description
15h Base Memory Size (in kB) - Low Byte
16h Base Memory Size (in kB) - High Byte
17h Extended Memory Size (in kB) - Low Byte
18h Extended Memory Size (in kB) - High Byte
19h Extended Drive Type - Hard Drive 0
1Ah Extended Drive Type - Hard Drive 1
1Bh Custom and Fixed (Hard) Drive Flags
Bits 7-6 = Reserved
Bit 5
= Internal Floppy Disk Controller
0 = Disabled
1 = Enabled
Bit 4 = Internal IDE Controller
0 = Disabled
1 = Enabled
Bit 3 = Hard Drive 0 Custom Flag
0 = Disabled
1 = Enabled
Bit 2 = Hard Drive 0 IDE Flag
0 = Disabled
1 = Enabled
Bit 1 = Hard Drive 1 Custom Flag
0 = Disabled
1 = Enabled
Bit 0 = Hard Drive 1 IDE Flag
0 = Disabled
1 = Enabled
1Ch Reserved
1Dh EMS Memory Size Low Byte
1Eh EMS Memory Size High Byte
1Fh - 24h Custom Drive Table 0
These 6 Bytes (48 bits) contain the following data:
Cylinders 10bits range 0-1023
Landing Zone 10bits range 0-1023
Write Precompensation 10bits range 0-1023
Heads 0 8bits range 0-15
Sectors/Track 0 8bits range 0-254
1Fh Byte 0
Bits 7-0 = Lower 8 bits of Cylinders
20h Byte 1
Bits 7-2 = Lower 6 bits of Landing Zone
Bits 1-0 = Upper 2 bits of Cylinders
21h Byte 2
Bits 7-4 = Lower 4 bits of Write Precompensation
Bits 3-0 = Upper 4 bits of Landing Zone
Continued...