80286 Adventures

Showcase your Retro PC / Build logs.

80286 Adventures

Postby keenmaster486 » 2019-3-10 @ 03:13

I finally have succumbed to my more basic instincts and acquired a 286 machine.

Here is a glamor shot of it just for kicks. I will post more detailed pictures later.
286_scaled.jpg



EDIT: Some more pics:

2.jpg

3.jpg


I found the unit on eBay for a reasonable price; it was listed as for parts due to not having a video card. One Oak 16-bit ISA VGA card later, and I was in business.

It will boot from a floppy disk. But the 43 MB RLL drive is giving me fits. The controller is a Seagate ST-21/22. What is strange about it is that the drive will spin up and make a lot of noise if you connect only the power without the data cables. But as soon as you hook up the wider data cable (not the narrower one), it will not spin up when you power on the machine. As I mentioned, this does not occur if you only hook up the narrow cable. With both cables connected the controller detects the drive (claiming it is an RLL drive) and wants to perform a low level format on it, but of course it cannot due to the drive not having spun up. I wonder what is causing this. I have very little experience with MFM/RLL drives so I really don't know what I'm doing here. Some quick searches don't turn up much on how to connect these things. Do I need to set something in the BIOS? The CMOS has Drive C: as "Not Installed". I tried setting it to Type 14 (43 MB) and it said "Drive C: Error" when booting. There's nothing on the drive that indicates what the geometry is, so I have no reference point as to which type I should set. I do notice that there are several that give a capacity of 43 MB. Maybe I should just try all of them until something works.

Anyway, this will be a lot of fun to play around with. Stay tuned to find out in what gruesome way I take my revenge on this hard drive when it begins to slowly eat away at my soul.
Last edited by keenmaster486 on 2019-4-22 @ 18:45, edited 1 time in total.
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby rmay635703 » 2019-3-10 @ 04:46

Maybe one cable is mounted backwards?

In any event I have never had a working rll drive, all the mfms still work great but RLLs always seem to be crapped out for some reason

Good Luck
rmay635703
Member
 
Posts: 105
Joined: 2019-1-19 @ 19:32

Re: 80286 Adventures

Postby retardware » 2019-3-10 @ 05:32

yes, take care to not put the cables the wrong way around!
There is almost always a pin 1 mark, make sure that cables are right around both ends.

MFM and RLL drives are the same, just the encoding/data rate is ~50% more effective, resulting in higher data density, and smaller bits that decay quicker.

You should low-level format by invoking debug, then entering g=c800:5 (or on some controllers g=c800:6) before judging the drive as bad.
If a drive does no longer work fine using RLL, you often still can use it with MFM.

Back then many people "overclocked" their drives by using RLL controllers on MFM drives. Worked fine if you had a good quality drive.

Regarding the drive type, just look up the label on the drive and then search specifications for your drive (c, h, s, precomp) using your favorite search engine to find out the type.
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby canthearu » 2019-3-10 @ 05:54

the debug command is only for XT based controllers with their BIOS.

Normally for AT/286 class computers, you would low level format through the system BIOS interface.
canthearu
Oldbie
 
Posts: 544
Joined: 2018-5-26 @ 01:00

Re: 80286 Adventures

Postby Jo22 » 2019-3-10 @ 16:30

Hi, nice machine! :)
Found a manual for the interface controller..

canthearu wrote:the debug command is only for XT based controllers with their BIOS.

Normally for AT/286 class computers, you would low level format through the system BIOS interface.

True. That's the same experience that I got as well. However, a few exotic 16-bit cards might had got their own BIOSes, still (who knows ?).
Perhaps because of the limited numbers of HDDs being hard-code into the main BIOS etc.
- Similar to these enhanced IDE controllers with their own ROM chip, I can imagine. :)
Attachments
st21-22.txt
ST21M/ST21R and ST22M/ST22R
ST412 Interface Controller Installation Guide
(26.76 KiB) Downloaded 7 times
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//
User avatar
Jo22
l33t
 
Posts: 3554
Joined: 2009-12-13 @ 07:06
Location: Europe

Re: 80286 Adventures

Postby retardware » 2019-3-10 @ 17:25

canthearu wrote:the debug command is only for XT based controllers with their BIOS.

Normally for AT/286 class computers, you would low level format through the system BIOS interface.

This applies only for MFM controllers that use the original WD100x (one of either 1003, 1006 or 1007 iirc, or compatible) MFM chip of the original IBM MFM controller.

Jo22 wrote:However, a few exotic 16-bit cards might had got their own BIOSes...

All other controllers thus had to provide a BIOS with formatter utility that supported the chips(et) they used.
Thus for *all* RLL controllers using the formatter provided by the cards' BIOS is the *only* correct way to low-level-format.

rmay635703 wrote:In any event I have never had a working rll drive, all the mfms still work great but RLLs always seem to be crapped out for some reason


Attempting to format using an incorrect (i.e. silently or loudly failing) method might be an explanation, as RLL drives were much more expensive (selected) ones with particular good properties.

Jo22 wrote:Perhaps because of the limited numbers of HDDs being hard-code into the main BIOS etc.
- Similar to these enhanced IDE controllers with their own ROM chip, I can imagine. :)

The consequence of that was the introduction of user definable types (usually 46, 47)
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-10 @ 21:20

I have achieved success, somewhat.

One of the cables was indeed upside down. I couldn't see this until I took the controller card out and looked at the numbers on the back.

After turning it over, the drive works, but has errors. I'm running CHKDSK now to see if it can fix them.
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby retardware » 2019-3-10 @ 21:31

Great!
In your place I would now do a clean low-level format, to make sure that you get a complete and current list of bad sectors that will get mapped out.
This is useful in particular if the drive developed new bad sectors over time, which are not yet mapped out as bad.
Else the drive will show errors every time you hit such a sector, which is not fun.

Edit:
My memory regarding the exact details already faded somewhat, but I remember I liked SpeedStor for entering and marking the bad block information manually, as DOS format does not recognize them reliably.
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-10 @ 22:02

I assume to do a clean low level format I should use the debug command you specified earlier.

I attempted a low level format using DOS 5.0's FORMAT utility, but it didn't work. FDISK said "Error reading fixed disk".
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby retardware » 2019-3-10 @ 22:15

Yes.
On HDDs, DOS "FORMAT" actually does no formatting (different than with diskettes, which it low-level formats).
it only writes the DOS filesystem data onto the HDD, which already has to be low-level formatted to have FDISK and FORMAT work.

After running the low level formatter via DEBUG, it should put out a list of bad sectors.
Copy (or photograph) this list, you'll need it later.
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby canthearu » 2019-3-10 @ 23:40

keenmaster486 wrote:I assume to do a clean low level format I should use the debug command you specified earlier.

I attempted a low level format using DOS 5.0's FORMAT utility, but it didn't work. FDISK said "Error reading fixed disk".


Low level format will be done by the system bios. 16bit MFM cards do not have a built in BIOS, so the debug command will not work (it is for the XT class machine only)
canthearu
Oldbie
 
Posts: 544
Joined: 2018-5-26 @ 01:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-11 @ 03:00

The debug command works. The Seagate I/O card BIOS pulls up and performs a low level format.

However, it fails to verify the format after it is complete, exiting with an error. After this, I can partition the drive with FDISK, but FORMAT chokes, churns and churns and eventually gives up.

I wonder how I can find the defects on the drive.
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby retardware » 2019-3-11 @ 03:40

What was the error message?

If you have a MFM controller, test low level formatting the drive using that.
For two reasons: its not always the drive which is bad. Bad cables and controllers also occur.
And, as MFM uses lower density, borderline drives might work fine witn MFM.
(You can reformat to RLL any time)

Does FDISK actually write the partition table, so it gets read back? (It does not tell if whe write attempt fails)
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-11 @ 03:51

I don’t have an MFM controller unfortunately.

Here is the error code:

B84806C5-2EDB-4E32-8777-08C6CDBADF7F.jpeg


I have been able to solve the problem temporarily, however, by simply making a partition that is a little less than the percentage of the drive that FORMAT gets through before hanging (i.e. 37%, so I made the partition 35%.) This seems to work fine. I can format it and install DOS.

It’s strange to me just how slow these old drives are. It’s almost as slow as a floppy disk in a high-speed floppy drive.
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby retardware » 2019-3-11 @ 04:13

Cool!

The error might be caused by wrong drive identification.
Say, data entered indicates a 800trk drive, and in case it is only a 300 trk drive, there will be a fatal error when trying to access track 301.
If this is the case, your "fix" by not using the part above, say, track 295 will work out fine.

To ensure there are no bad blocks in lack of low level format verification data, you can use things like the pctools drive test (with write test enabled!), to find bad blocks and mark them so DOS does not use these.

BTW, speed is relative... these 3600rpm MFM drives with their 17 sectors were blazing fast compared to floppy disks :)
Imagine, my first HDD on my XT in the mid-1980s (ST-212) made a whopping 80kB/sec sequential read throughput.
The later transition to a ST-4096 (not sure whether I remember the number correctly) "overdriven" by an 8bit Adaptec ISA RLL controller increased the transfer rate to a whopping 120kB/sec!
And then compare this with the floppy's approximate 5kB/sec! And the seek times... average 80ms iirc. That was about the track-to-track seek time of the floppy... wow :)

(Anyway make sure that you haven't set the interleave lower than the system can process... if your system can process interleave 2 and you set interleave 1, the access + latency times will increase 1000+%)
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-11 @ 04:42

Interesting.

I have no way of knowing whether the drive is being detected incorrectly. However, I do know that the partition that was on there before I low-level formatted was created in 1992, and was also 11 MB large (i.e. about 35% of the drive, same as the one I just made). So either somebody else ran into this same problem 27 years ago, or the drive is smaller than I thought. But it does say 43MB on it.

I'll see if I can test it with a drive test tool.

I have set it to interleave 1! Perhaps interleave 2 would work better? I could try that and see what happens, although of course I will have to low level format it again.
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby retardware » 2019-3-11 @ 11:35

keenmaster486 wrote:I have no way of knowing whether the drive is being detected incorrectly.

There is no hardware detection in the MFM/RLL interface.
The "detection" has to be done by the user.
It involves looking at the label and then looking up the drive specification in the web.
Usually near the type sticker (or even on itself) there is the defects list.
Ideally just take a photograph of that, so we can work based on hard facts instead of guessing.

keenmaster486 wrote:However, I do know that the partition that was on there before I low-level formatted was created in 1992, and was also 11 MB large (i.e. about 35% of the drive, same as the one I just made). So either somebody else ran into this same problem 27 years ago, or the drive is smaller than I thought. But it does say 43MB on it.

Well, I am still not sure what gave the information "43MB". The label? The (possibly incorrect) size in the partition table?

keenmaster486 wrote:I have set it to interleave 1! Perhaps interleave 2 would work better? I could try that and see what happens, although of course I will have to low level format it again.

You can calculate whether the interleave is too low by calculating from the measured sequential read speed.
If the interleave is too low, the next sector being to be read has already slipped away when the previous sector has been read and the computer is ready to process the next sector. Then one has to wait for a full platter revolution to read the next sector, leading to an access speed/efficiency of only 1 sector per revolution.

The interleave means how the sectors are ordered:
1: 1 2 3 4 5 6 7 8 9
3: 1 4 7 2 5 8 3 6 9

one RLL track = 26 sectors = 13kB
3600rpm = 60 rps => theoretical maximum transfer rate = 60x13kB = 780kB
and then think slow 4.77 machine with slow custom controller bios etc -> high interleave factor was common
in contrast, 386+ usually were able to handle interleave 1

only sure way to find out is to try out and find at which interleave the performance drops sharply compared to the next-higher one.
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-11 @ 16:10

Does setting the interleave higher mean that I will no longer be able to dodge the bad areas of the disk by creating a smaller partition?

Also, the only information on the label on the disk is that it is a “Packintell Model 43MB”. That’s it. No other information. The defect list has not been populated.
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Re: 80286 Adventures

Postby retardware » 2019-3-11 @ 17:56

Changing the interleave only orders the sectors differently.
The idea behind this is that the next sector reaches the heads not before the processing of the previous sector has been completed.
Only effect of setting it higher than necessary is increased latency (=less performance).

Never have heard of a HDD manufacturer named "Packintell".
Sounds to me like some long forgotten OEM brand.
I'd suggest you take the HDD out of the case, make some photos and open a thread "Can anybody identify that HDD?".

In case we can identify original manufacturer and the series, we can narrow down to a particular type, to know the correct C/H/S/Precomp values to make full use of the drive.
retardware
Oldbie
 
Posts: 552
Joined: 2019-1-30 @ 02:00

Re: 80286 Adventures

Postby keenmaster486 » 2019-3-13 @ 15:50

I set the interleave to 2 and reformatted - also I think I have figured out that it is an 818 cylinder drive because it chokes while formatting if the cylinders are set higher than that. Still can't verify the format though.

I will be posting pictures later.

It is strange to me, though, that the formatting utility will get very far at all formatting with different C/H/S settings; you would think it would just exit with an error if it was not correct. How could it format for 5 heads when there are only 4, for example?
I flermmed the plootash just like you asked.

http://classictechnology.herokuapp.com
http://keenmaster486.github.io
Vintage desktops: Pentium/MMX 233 (Win95), 286-12 (MS-DOS 5.0)
Vintage laptops: IBM Thinkpad 600E, 560X, 365CD
User avatar
keenmaster486
Oldbie
 
Posts: 1662
Joined: 2016-2-16 @ 02:04
Location: Atroxus

Next

Return to System Specs

Who is online

Users browsing this forum: No registered users and 3 guests