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More discussion on the PC-DOS 1.10 boot sector and how it compares to the COMPAQ 1.11 boot sector

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Jeff Parsons 2017-07-01 12:21:06 -07:00 • committed by Jeff Parsons
commit 6d16f582c7
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12
disks/pcx86/dos/compaq/1.11/README.md
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@ -302,9 +302,15 @@ look at the code, using the PCjs Debugger to stop at the first instruction:
&7DE4 00 00 00 E7 01 00 00 00-00 00 00 00 00 00 00 00 ................
&7DF4 00 00 00 00 00 00 00 00-00 00 00 00
In terms of raw code (90 instructions), it's shorter than the PC-DOS 1.00 boot sector (99 instructions),
even though it supports twice as many disk formats. This is because it uses tables to describe both the
different disk formats *and* the discrete read operations, relieving the code from dealing with track boundaries.
In terms of raw code (90 instructions), it's shorter than both the
[PC-DOS 1.00 Boot Sector](/disks/pcx86/dos/ibm/1.00/#pc-dos-100-boot-sector) (99 instructions) and
[PC-DOS 1.10 Boot Sector](/disks/pcx86/dos/ibm/1.10/#pc-dos-110-boot-sector) (116 instructions),
because it uses tables to describe both the different disk formats *and* the discrete read operations,
relieving the code from dealing with head and track size calculations.
It's arguably an improvement over the [PC-DOS 1.10 Boot Sector](/disks/pcx86/dos/ibm/1.10/#pc-dos-110-boot-sector),
because it didn't need to be altered to support both 160Kb and 320Kb diskettes. On the other hand, that flexibility
also makes it slightly slower to boot, because it must read the first FAT sector to determine the diskette format.
### Mounting the COMPAQ MS-DOS 1.11 Diskette