les@etn-rad.UUCP (Les Beears) (11/11/87)
I need to connect three hard disks to my MS DOS PC AT. DOS seems only to be able to support two hard drives, at least that is what everyone "in the know" seems to agree to. Does anyone out there know of a controller which can be used to support three drives? Perhaps I could use two controllers and somehow modify a DOS driver. Can anyone out there advise me on this approach? I hope I don't have to convert the system over to a SCSI configuration. Please mail responses to : ihnp4!wlbr!etn-rad!les or voder!wlbr!etn-rad!les Thanks L. W. Beears
guardian@laidbak.UUCP (Harry Skelton) (11/12/87)
A westren digital controler will do what you want. You can plug two of them
in and set the second controler address to just above the first. i.e. make
the first rom address at c800 like most HD's and set the second at the next
slot above that (see your manual for details or call WD for more info).
I have a WD and a Xebec controler in my machine. My WD is set for HD
controler #2. Works great!
.---------. OO OOOO OO
Harry Skelton : .-. : OO OO
guardian@laidbak.UUCP : `-'o : OO OOOO OO
{sun, spl1, ihnp4}!laidbak!guardian : O : OO O O OO
`---------' OO OOOO OO
The Far Seek ... Tales from the bad sector. OO
"As 'panic traps' appear across the console, Edward, once OOOOOOOOOO
again, finds Harry scratching his back against the
disk drives."del@pilchuck.Data-IO.COM (Erik Lindberg) (11/14/87)
In article <301@etn-rad.UUCP> les@etn-rad.UUCP (Les Beears) writes: >I need to connect three hard disks to my MS DOS PC AT. DOS seems only ...... >use two controllers and somehow modify a DOS driver. Can anyone out >there advise me on this approach? I hope I don't have to convert the I have connected multiple (>2) drives to systems before. DOS doesn't care in the slightest how many drives you connect (up to # of available letters), it is the BUS and disk controller hardware that is your limitation. Hardware wise, there are a limited number of physical interrupt lines available on the PC bus, a few more on the AT bus, but most cards can't use them anyway. Also, the port decoding is incomplete in the PC family, i.e. not all the address lines are actually decoded by the hardware so you are limited as to how many ports you can have. The controller cards typically only provide two data ports for drives, so you can't put more than that on one card, and consequently the BIOS doesn't support more than two drives anyway. You wanted solutions, right? You mentioned one yourself, which would be my choice for any implementations I would do in the future: SCSI. That is by far the easiest and most flexible long term solution. You can put *anything* out there, including 9 track tape drives and 8" disks, if you want. Alternatively, I have done several implementations using an old (no longer manufactured but occasionally available) add on controller from Datamac, it is so old it came out before the XT. Consequently there was no standard for what the interface should look like and what address it should be at. Luck holds and they don't interfere with anything! You still have to write a device driver to go with it, unless you can find someone willing to sell/give you one that works with that controller. (I can't, they're proprietary). In addition to the Datamac controller, I believe DTC manufactures (or did) a controller that allows changing the addressing on the card, allowing you to install two in one machine, but they provide no software to support it. Finally, "most amount of work" award goes to this solution. Take any old controller (no surface mount, unless you are *really* good:-) and butcher it to respond to different addresses. Could be tough since most companies don't want to give you schematics :-( THEN write your own software to run it. -- del (Erik Lindberg) uw-beaver!tikal!pilchuck!del