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1988-03-23
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Sparta PCBoard
Hard Drive Conference
(201) 729-7056
August 8, 1987
This is the second in a series of informational files about the Perstor
200 series hard drive controllers... The model PS180 and model PS200.
Drive Tables
____________
Perstor will soon be issuing new BIOS Eproms for the PS180 and PS200
controllers that will have 16 hard drive table entries contained in the
Eprom. You will be able to select from one of four tables, with each
table containing information for 4 drives. This should reduce the
number of controllers shipped that have to have a new Eprom burned to
match your hard drive configuration. Of course, we will still be able
to burn HD track and cylinder information into the Eprom if you have a
drive that is not included in the factory Eprom.
Interleave Determination
________________________
A subject that always makes for lively discussion. I have been asked
many times about the factory recommended interleave value that may seem
awfully high compared to one that you might have been using with a
standard 2,7 RLL controller such as the OMTI. I have also inquired of
Perstor about those values. Their reply was essentially what I thought
it would be. The interleave values are subject to change according to
system components that make up the whole system, not just the
controller and hard disk. The factory recommended settings are actually
halved by the Perstor BIOS because of the interleave skew pattern that
is put on the drive by PS2FMT when doing the low level format. If you
specifiy an interleave of 4, then your transfer rate should be equal to
or better than if you had used an interleave of 2 on an OMTI.
The bottom line on what the interleave should be for your configuration
should be based on your own testing of the system as a whole. Different
systems, at different clock speeds, various memory board and chip speed
access, DMA channel efficiency and speed, all affect what your
interleave might eventually wind up being. In the following paragraph,
I am going to show you a quick and dirty way to quickly find the best
interleave for your system.
1. Make all necessary connections to the hard drive to the Perstor
controller as you would with any other controller.
2. Boot from a DOS equipped floppy drive and then switch to the Perstor
diskette furnished with your PS-180 or PS-200 controller. Execute the
PS2FMT low level formatting program.
3. Select the appropriate drive for formatting and select an interleave
to begin your testing with. Record on a sheet of paper your interleave
factor used for this step.
4. Allow the formatting program to run for 1 minute. Reboot the
computer and execute the Coretest 2.7 analyzer program. Record your
data transfer rate for the current interleave being used.
5. Repeat the procedure in steps 2, 3, and 4, above until you find
where your maximum data transfer rate is achieved. At that point, do a
clean boot, execute PS2FMT and low level the entire HD using the
interleave that gave you the best transfer rate.
6. Please note that you should always use the manufacturers low level
formatting program as opposed to the low level formatter furnished with
Vfeature, Disk Manager, or SpeedStor.
Would you believe 71MB on a ST-238
__________________________________
I have come up with a couple of configurations for the ST-225 and ST238
drives that have allowed a couple of purchasers of the Perstor
Controller to break the 140MB barrier on just two Seagate drives. Here
is the configuration that I have devised.
Using a typical Seagate 20MB drive, you have 4 heads, 615 cylinders at
your disposal. On a regular MFM controller you will get your regular
20MB of rotating memory. On an Omti 5527, WD1002-27X, DTC 5150CX, or
Adaptec ACB-2070A RLL controller you should be able to format the drive
out to about 32MB and change. With the Perstor PS-180 Controller, you
can format this drive out to 38.13MB. Now, you ask, where does all that
extra megabytes come from? By using the Perstor HD Compression
software, that's how.
The secret in getting the maximum benefit from the compression software
is to set up a partition no bigger than 16MB to use the utility on.
Here is a typical situation where you could get 54.72MB, assuming you
needed a large boot partition, let's say in the neighborhood of 20MB.
1. Format the drive using PS2FMT. Run FDISK and choose 350 cylinders
for the first partition. At this point, exit FDISK and run the DOS
Format.com program to high level format the first partition.
Format C: /S/V will high level format, place the operating system on
the partition and prompt you for a volume label. After this, run chkdsk
and see if you have about 22,220,800 bytes of storage on the first
logical drive.
2. Now this leaves 265 cylinders unaccounted for. We are now going to
get the Perstor PSE2FMT program going. When this program is executed,
you will see a screen that looks just like FDISK. You are now going to
create a second partition on the HD with this program. Just tell PSE2
that you wish to use the remaining 265 cylinders for the second
partition. The partition will be created and high level formatted all
in one step. It is then necessary that you install the perstor driver
in your config.sys file with the appropriate device= statement.
3. Now what you will see when you run chkdsk on this second partition
is a 33MB partition. Do not fret that it only show 16mb free. Let the
driver do it's work. You will be able to put 33mb worth of data on the
partition. The driver will take approximately 20K of RAM from your
640K. Well worth it to get this kind of increased storage upstairs.
Now for scenario number two where you can get 71.2MB on the drive.
1. Do the low level format with PS2FMT.
2. Using FDISK, create a partition using only 85 cylinders. High level
format this partition with the normal Format x /s/v where x is the
drive letter to be formatted.
3. Using PSE2FMT, create 2 partitions of 265 cylinders each. This
should give you 16.4MB of physical room on each of the two partitions.
4. When you get through with the PSE2 program, you should now have a
drive with 5,396,480 bytes (5.2mb) on it in the first partition and two
(2) partitions of 33MB each, for a total of 71.2MB.
Don't ask me how it works, boss! It just does.
The next bulletin in this series of informational files will be
Perstor2.arc. Call Sparta PCBoard @ (201) 729-7056 to get the latest
information on these fine controllers.
Richard Driggers
Sysop