PDA

View Full Version : Temperamental A)IBM XT B)ST-225 C)Controller D)All of the above?



6885P5H
May 9th, 2017, 11:32 PM
Hello. My IBM XT has issues with its Seagate ST-225 hard drive. And it always had actually since I got it last year. I made a post around the time I got it here and in that post I mention the exact same hard drive problem. The problem is as follows. Sometimes, I will turn the computer on and the hard drive will work no problem. Other times, the hard drive will work at first but become unreadable after. Other times, the hard drive cannot be read from the moment it is powered on. Interestingly, when the hard drive is unreadable it is still detected by the computer, can still be accessed (but not read) and can still be parked. It sorts of act like as if it wasn't low-level formatted, I guess. Also interesting is that when it becomes unreadable its drive letter disappears from DOS. Typing C: does not say something like drive not ready, read error etc... It just says something like invalid drive letter even though previously in the same session it was there and readable! And when the drive is readable all the data is there and can be read flawlessly. So I don't know if it's a problem with the hard drive, the controller, or the computer itself... The controller is a DTC 5150BX I think.

So that's the problem. Just looking at the controller itself makes me feel extremely anxious. There seems to be two ROMs but at least they are socketed. I don't know how to read them however. There are also 2 soldered PALs, and there seems to be many rare and proprietary parts on it.

And interestingly, the hard drive seems to be connected backward to the controller. The pink stripes on the cables go from the first pins of the hard drive to the last ones of the controller... I didn't even know this was possible.

modem7
May 10th, 2017, 01:38 AM
So I don't know if it's a problem with the hard drive, the controller, or the computer itself...
You left out: bad connections, cables (http://minuszerodegrees.net/misc/suspicious_cable.jpg)and power.

For example. I have had intermittent hard drive problems caused by the connection from power supply to drive (plug into socket) not being as snug as it should.

Dirty edge connectors.

Many possibilities. I have spares of everything, and one advantage of that is so that in your kind of situation, I can norrow in on the cause of an intermittent problem relatively quickly.


The controller is a DTC 5150BX I think
Both variations of DTC 5150BX that I have seen have "5150BX" printed on them.


And interestingly, the hard drive seems to be connected backward to the controller. The pink stripes on the cables go from the first pins of the hard drive to the last ones of the controller... I didn't even know this was possible.
"First pins" and "last pins" do not always indicate the end where pin 1 is.

6885P5H
May 11th, 2017, 10:28 AM
Currently the hard drive works. I re-partitioned it but it is unformattable. I can put some files on it but cannot sys it. I've never messed with an MFM hard drive before... When I attempt to format it it just gets lost for what seems like an eternity....

Stone
May 11th, 2017, 10:34 AM
Currently the hard drive works. I re-partitioned it but it is unformattable. ....Kinda' a contradiction, doncha' think? :-)

6885P5H
May 11th, 2017, 11:15 AM
Huhmmm, it works as in it doesn't act up in the way that I described above. If it didn't work, typing format c: would say something like drive not found.

I don't know how these hard drives are supposed to work. Maybe I need to format it with a special utility I don't know ;(((( I'm afraid to mess something up, maybe I already did.

fatwizard
May 11th, 2017, 12:59 PM
Have you done a low level format on the drive? It has helped, or been absolutely necessary with nearly all the old MFM drives I have gotten. Many 8bit controllers have a low level format routine in the ROM, accessed from DOS by entering debug, and typing G=C800:5

6885P5H
May 11th, 2017, 03:35 PM
No I haven't tried that. This is something that I have never done before and I'm afraid I could mess something up... I know that G=C800:5 (goto address C800, I don't know what the 5 means) is the generic method of performing a low-level format. I'd be interested in having a list of all the commands available for my controller. Maybe the generic command doesn't even work with it, I never tried it.



**Off-topic** Apparently the 5 is an offset. I kinda forgot what an offset was but I think it means the fifth byte starting from C800. So G=C805 would work if the IBM XT had a 5-bit processor.... Hahaha probably not... I really don't remember how this stuff works.... I used to know what integers were. Words, longwords, shortwords... I forgot all of it.

6885P5H
May 11th, 2017, 03:46 PM
If doing a low-level format is required to format it in DOS, can I have some instructions? The controller asks me for an hard drive number. And after that an interleave factor.... And who knows what's next. Cylinders, heads, whatever else is written on TH99, I can write. The rest, I don't know what it is.

SpidersWeb
May 11th, 2017, 03:50 PM
I just wanted to agree with fatwizard said above. I do it on all my machines when they arrive because it's only a matter of time before it wont be able to find it's marbles anymore.

Low Level Format, then partition in FDISK, then format with DOS.
It'll be blank, but likely work like a charm for years to come afterwards.

Edit: Drive number would be 0, interleave on a 4.77Mhz XT .... I think 5 would be ideal.

Heads 4
Tracks/Cylinders 615
Sectors per track: 17
Write Precomp: 300
Reduced Write: 616

Shouldn't need much else?

6885P5H
May 11th, 2017, 05:07 PM
This hard drive used to work fine (when it didn't act up). I deleted its partition, created a new one. I then saw that it couldn't be formatted. And now it's stuck in a weird state where files can be put on it, but it cannot be sys'd and a few other oddities (like chkdsk saying that the disk is a probable non-dos disk). A low-level format could fix this? Maybe.

Can you tell me what drive number and interleave are? Why do you say 0 and 5? The controller says that the default interleave is 6 by the way.

What is reduced write, where did you get that info?

SpidersWeb
May 11th, 2017, 06:13 PM
Drive 0 is normally the first drive in the chain. If it doesn't accept 0, try 1. It can vary depending on who wrote the formatting program.

Interleave is how far the sectors are out of order. An IBM PC XT is too slow to read one sector after another, so you spread them out to prevent the machine from accidentally missing one and having to wait for the drive to spin all the way around again to read the next. From memory 5 is just what I've use on my XT's. I'm sure 6 would be fine if you prefer the default. Others might also comment on their results, I just wanted to give you something quick to get it running.

I got the other numbers from Seagate - ftp://ftp.seagate.com/techsuppt/mfm/st225.txt

Reduced Write - I believe for reliable writing, some drives needed the electrical current sent through the write heads to be reduced once they got past a certain cylinder on the disk or vice versa. I've never really looked in to it too much, just entered the number when asked.

SomeGuy
May 11th, 2017, 07:05 PM
Can you tell me what drive number and interleave are? Why do you say 0 and 5? The controller says that the default interleave is 6 by the way.
Interesting. What model of hard disk controller are you using? Most 8-bit MFM (17 sector) hard disk controllers that I have seen have a default interleave of 3. 8-bit RLL controllers, on the other hand may have a higher interleave because they have more sectors. You haven't gotten an RLL controller attached to an MFM drive have you?

Of course, normally you would just use whatever default interleave the card suggests. You can optimize it later by running Spinrite.

The problem described sounds like a weak sector on track zero. Low level formatting may fix the problem, but you should keep an eye on it. After installing DOS, running spinrite may also help verify that the drive is physically OK.

6885P5H
May 11th, 2017, 09:28 PM
Very good explanation SpidersWeb!

It didn't even ask me anything other than the drive number and interleave. Everything else must be set in the DIP switches but interestingly on TH99 there are no switch combinations that correspond with the parameters of the ST-225... It's set for a 15MB hard drive but the entire 20MB of the drive seem to be usable.


DTC 5150BX. It's not an RLL controller. It looks pretty old...

I low-level formatted it, partitioned it, DOS-formatted it and sys'd it. Seems to work fine...

Does someone have the software for the Paradise Systems 5PAK or 5-Pack? The clock program fortunately came with the computer and it seems to work great but there were other programs that came with it according to its ad.

SpidersWeb
May 12th, 2017, 02:58 AM
Awesome it's working. I've noticed with those cards it's common to get different BIOS revisions, yours probably does have a 615 4 entry for an ST-225.

I don't have the Paradise card, but you could try some of the utilities on modem7's site http://minuszerodegrees.net/rtc.htm if nobody posts up the actual driver.
One of them will likely work for the clock.

6885P5H
May 12th, 2017, 11:55 AM
Well, I have the original clock program that came with the board. But according to the ad for it it also came with a printer program, a RAM drive program... Not that I really want to use these features, but I think it would be a huge shame if these programs were lost forever. I could look more in-depth but they don't appear to have come with the computer.

And this is why I always copy the entire content of a drive (and image it when that is possible) before formatting it. I even look for deleted files. I am very paranoid about this stuff, if I had just formatted the drive without looking into it then the Paradise clock program may have been lost forever. I find it very disturbing that if you want to use an MFM hard drive you need to use it with the controller it was low-level formatted it. If you don't know with what controller it was used with before, it's format time. I have a small bunch of MFM hard drives. Guess I'll have to format them if I want to use them but what if they contain the last remaining copies of a program or a driver...

I have a bunch of diskettes that I haven't created images of because they were empty. But I haven't checked them for deleted files; way too much work. But I know that they contain some insanely rare programs. I know because, I took a random empty disk and looked into its deleted files. I was able to recover some kind of program. I looked it up online and it brought up absolutely nothing. I may have the last copy in existence of this program. I'm sure I have a lot of files like that but it would be simply too much work... Even the Paradise card makes me anxious. It has 2 PALs soldered to it. Those are parts that you cannot replace because they are programmable chips, so they come blank when you buy them.... They can be cloned but even unsoldering them is far beyond my skill...


If anyone wants the Paradise clock program I uploaded it here: https://ufile.io/l9avl the file will stay there for 30 days.

modem7
May 12th, 2017, 05:49 PM
If anyone wants the Paradise clock program I uploaded it here: https://ufile.io/l9avl the file will stay there for 30 days.
I have added the clock program to http://minuszerodegrees.net/rtc.htm