Path: utzoo!utgpu!attcan!uunet!husc6!mailrus!ames!vsi1!octopus!pete
From: pete@octopus.UUCP (Pete Holzmann)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Recommendations wanted for large (>100 Mb) hard disks
Message-ID: <357@octopus.UUCP>
Date: 29 Sep 88 04:59:14 GMT
References: <29.233DBDD4@busker.FIDONET.ORG> <3995@tekgvs.GVS.TEK.COM> <11769@emerald.BBN.COM>
Reply-To: pete@octopus.UUCP (Pete Holzmann)
Distribution: na
Organization: Octopus Enterprises, Cupertino CA
Lines: 41

It *is* DOS that can't handle more than 1024 cylinders. You need a device
driver that hides the extra cylinders somehow.

The most common method seems to be to have a custom device driver
(Ontrack=DMDRVR.SYS, Speedstor=HARDRIV.SYS, Adaptec boards come with
ADAPTEC.SYS) that can access above 1024 cylinders and make them look like
an extra physical disk to DOS. The best and cheapest version I've seen
is to get an Adaptec controller of your choice. Its low level format
program (built into the ROM BIOS) can handle all this, including download
of the device driver onto your disk!

Another method is to fake everything up to make it look like there are
fewer cylinders. As mentioned elsewhere, Future Domain can use larger
sector sizes and act as if there are fewer cylinders (i.e. tell the
operating system that you've got a normal number of sectors per track,
but actually have only 1/4 as many or whatever, and do the translation
on the fly).

Personally, I like what some others have done, including Adaptec in their
latest BIOS revs: they use normal sector sizes, but you can fake things
up so it looks like there are 63 sectors per track; the board does the
logical to physical translation on the fly as with the big-sector method.
What is nice about this method is that you don't waste a gob of space for
each small file on your system, and random record access needn't suffer
from pulling in a giant sector when you only need a small chunk of data.

Anyway, handling cylinders beyond 1024 is not too big an issue any more,
as long as you are using the latest rev levels of SpeedStore, Disk Manager,
and most main stream controllers.

By the way: the wholesale price on Adaptec 2372 controllers dropped 35-40
bucks recently, presumably due to volume. This should show up real soon
in regular pricing, making 1:1 RLL only about 20 bucks more expensive than
ST506!

Pete
-- 
  OOO   __| ___      Peter Holzmann, Octopus Enterprises
 OOOOOOO___/ _______ USPS: 19611 La Mar Court, Cupertino, CA 95014
  OOOOO \___/        UUCP: {hpda,pyramid}!octopus!pete
___| \_____          Phone: 408/996-7746