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Tandy 1000HD Hard Disk SpeedUp
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The 5 1/4th inch 10 megabyte Tandon Hard Disk Drive that comes standard
on the Tandy 1000HD is a durable piece of equipment, though not the fastest.
Using the Core Hard Disk Performance Test version 2.7, the drive (hard
sectored by the program HSECT.COM on the Tandy HARD DISK UTILITIES disk
supplied with the machine) and running PC DOS 3.2, reveals the following:
Data Transfer Rate = 100 kilobytes/sec
Average seek time = 97 msec
Average track to track = 17 msec
While nothing can be done about the last two figures (hardware dependent),
the data transfer rate can be optimized to 125 KB/sec, a 25% improvement
by optimizing the interleave factor (software dependent) when hard formatting
the disk.
Alter the interleave factor, you may ask? Yes, the Western Digital Controller
Board as supplied with the Tandy 1000HD has a formatting program in ROM,
which is slightly different from those WDC controller boards supplied by
third party vendors. Through trial and error, I found that using an
interleave factor of 4 optimized disk performance, obtaining the following
results:
Data Transfer Rate Interleave Factor
(KB/sec)
28.4 1
27.1 2
28.5 3
124.6 4
100.5 5
83.6 6
72.0 7
It appears that the HSECT.COM program uses an interleave factor of 5. To
reformat your hard disk, follow these instructions:
1. Make a backup copy of all files on your Hard Disk--they will be
destroyed by this procedure.
2. Type "debug" at the DOS prompt, then type:
-r ax <cr>
AX 0000
:0004 <cr> {Enter the value of 0004 into register AX}
-g=C800:05 {Execute Code beginning at address C800:0005.
You will then be prompted to answer (y)es or (n)o to hard sector
format the Disk Drive using an interleave factor of 4. Type "y".
Upon completion of the task, you will be returned to the DOS prompt.
3. Now simply reformat the hard disk using HFORMAT (MS-DOS 2.11.22)
or the FORMAT command of PC-DOS 2.10 or higher.
It is to your advantage to use PC-DOS 3.1 or 3.2. Using the DOS31.PAT and
DOS32.PAT files found in the IBM Sig Data Libraries, you can modify your
10 megabyte disk drive into clusters of 2048 bytes (4 sectors). PC and MS-DOS
below 3.0 formats all disks into 4096 byte clusters (8 sectors). DOS 3.0,3.1
and 3.2 format 19 megabyte or smaller drives with 8 sector clusters, and
larger drives with 4 sector clusters. By modifying the boot record on sector
0 track 0 as outlined in the DOS3x.PAT files, you can fool DOS (3.1 or 3.2
only !) into using the smaller sector cluster allocations. The advantage is
an average saving of 10-15% of disk space that would otherwise be wasted on
smaller file sizes. This is the result of using 16 bit entries in the File
Allocation Table, instead of the usual 12 bit numbers. As a specific example,
if you have a 760 byte file, DOS allocates 4096 byte (8 sectors) of disk space
to that file when using the 12bit FAT entry, versus 2048 byte (4 sectors)
with the 16 bit FAT entry.
I can only verify the speed results using PC-DOS 3.2 on the Tandy 1000HD.
I will be comparing MS-DOS 2.11.22, MS-DOS 3.1, and PC-DOS 3.1 to determine
possible differences in speed between operating systems and whether the
interleave factor is independent of them.