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Rolf
March 2nd, 2005, 03:56 AM
G'day Guys. I need to make controllers talk to MFM disks.
Specifically, a controller currently running a dying 40MB disk, being reconfigured to run a 32 MB disk.
Years ago I was given a DEBUG procedure to Low Level Format.
DEBUG (enter)
g=c800:5 (enter)
I recall 5 as the Interleave, but I can't remember what g=c800 is.
***********************
Also any info please, on running 2 different capacity hard disks from the one controller.

carlsson
March 2nd, 2005, 04:21 AM
A long shot - isn't c800 the hexadecimal memory address you will call? I.e. what you do is to execute (g = go) a routine loaded into RAM (or ROM), but what the argument after the colon is, I couldn't tell. If there is no user interface to the controller, maybe a skilled PC (I assume) hacker could disassemble the routine that happens to start at $c800 and figure out if there are some other entry points to reconfigure the controller.

lither
March 2nd, 2005, 05:12 AM
[quote="Rolf"]G'day Guys. I need to make controllers talk to MFM disks.
Specifically, a controller currently running a dying 40MB disk, being reconfigured to run a 32 MB disk.
Years ago I was given a DEBUG procedure to Low Level Format.
DEBUG (enter)
g=c800:5 (enter)
I recall 5 as the Interleave, but I can't remember what g=c800 is.
***********************

no ,the "5" is not the interleave , it is the offset of the address
the command "g=C800:5" means run from the address "C800:5"(it is due to the register of the 8088/8086 is 16 bit but the 8088/8086 could address up to 20bit=1M .)
all you need to know is the address of bios of your card
in most case , it is C000,C800 ,......
if you are sure you have type C800 in this card , just do

DEBUG (enter)
g=c800:5 (enter)

usually it will pop a program and you can configure your card again
as for setting of two MFM disk , i have not done this before but i have heard a rumor that you'd better use two identical disk esp in an old controller.

Terry Yager
March 2nd, 2005, 06:47 AM
Some MFM controllers don't have ll formatting programs, and some have it at a diffeferent address than the c800:5 one. Getting two drives to work together on a single chain usually isn't much of a problem. Just make sure that one is addressed as device 0, and the other is device 1. Also, the last drive on the chain needs a termination resistor block installed, and none on the other one. Then, just daisy-chain the 34-pin cable to both drives, and one of the 20-pin cables to each one. (It makes a difference which 20-pin cable goes to which drive, as they are hard-wired on the controller card to be first drive & second). If one or both drives need to be ll formatted, the ll format program allows you to choose which drive to format. (It'll also prompt you with some other questions that you'll need to know the correct answers to, such as, number of heads, number of cylinders, first cylinder, last cylinder, write precomp, landing zone, and prob'ly a few more which evade me at the moment). Do not attempt to ll format an MFM disk until you have armed yourself with the necessary information.

--T

barryp
March 2nd, 2005, 05:25 PM
G'day Guys. I need to make controllers talk to MFM disks.


I've gone the debug route but Ontrack's DiskManager is much easier.

Rolf
March 3rd, 2005, 06:50 AM
Update is the 32MB disk is a Seagate 238R. It's existing controller runs it as a 20MB unit. It is an RLL drive, so I guess now I gotta find a friendly controller. Thoughts please.
At ur convenience, please checkout the Software Forum re Win v1.01.

Terry Yager
March 3rd, 2005, 08:39 AM
Update is the 32MB disk is a Seagate 238R. It's existing controller runs it as a 20MB unit. It is an RLL drive, so I guess now I gotta find a friendly controller. Thoughts please.
At ur convenience, please checkout the Software Forum re Win v1.01.

I've never tried it but other folks have reported only mixed success in RLL formatting a drive that has been (incorrectly) formatted as MFM. Sometimes they'll come back and sometimes not. Good luck, hope it works out for ya.

--T

barryp
March 3rd, 2005, 06:10 PM
I've never tried it but other folks have reported only mixed success in RLL formatting a drive that has been (incorrectly) formatted as MFM. Sometimes they'll come back and sometimes not.

I've gone back and forth with drives. Never had much trouble. (Might take >1 format)

Terry Yager
March 3rd, 2005, 06:14 PM
Oh, I'll keep that in mind, in case it ever comes up.

--T

mbbrutman
March 5th, 2005, 06:52 AM
Somebody already pointed out that C800:5 is a segment and offset combination. If the drive controller has a BIOS at C800, this was the customary place for the built in formatting routine.

RLL drives are designed to a higher quality spec than MFM drives. You should be able to run an RLL drive as plain MFM - it's not as strenuous. Formatting an MFM drive as RLL might work, but I would trust the data.

Anonymous Coward
March 6th, 2005, 07:02 PM
If you want a good controller for an MFM or an RLL drive, I highly recommend the Western Digital 1002 series. You should look them up on TH99. The 1002A-27X (RLL) and 1002A-WX1 (MFM) are the way to go. I own both of these controllers, and they are quite nice. The 1002-27X is also fairly decent, but doesn't support drives over 32MB, while the first two I mentioned do.

Rolf
March 7th, 2005, 03:33 AM
Thanx for the input.
So where do I find the WD controller? :)

Anonymous Coward
March 7th, 2005, 07:17 PM
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4193&item=5171496638&rd=1&ssPageName=WD1V

However, it's a wee bit expensive.

barryp
March 8th, 2005, 05:28 PM
Thanx for the input.
So where do I find the WD controller? :)

I prolly have some... $5?

Entropyk
November 5th, 2016, 12:27 PM
G'day Guys. I need to make controllers talk to MFM disks.
Specifically, a controller currently running a dying 40MB disk, being reconfigured to run a 32 MB disk.
Years ago I was given a DEBUG procedure to Low Level Format.
DEBUG (enter)
g=c800:5 (enter)
I recall 5 as the Interleave, but I can't remember what g=c800 is.
***********************
Also any info please, on running 2 different capacity hard disks from the one controller.

The command g=c800:5 means to go to that address in memory and run the program there. When you ran it, you would find a list of hdd's by name and capacity that you could install by selecting them off the list by the number and poof it was done. If it was not on the list you had to select the number for manual installation and enter the number of sectors, heads, and cylinders. It usually worked pretty well. I believe you needed a separate controller for each drive back when I was doing it. (Started in XT, PC Jr days).

David_M
November 5th, 2016, 10:53 PM
Since you are in Melbourne like me, I have some AT MFM controllers and can give you one for free if you want to collect one. I may even have and RLL controller, I haven't looked at them that closely.