Copying DEC VAX set up disks rx50, help
dave06a at dunfield.com
Sun Mar 4 06:00:53 CST 2007
> Image Disk reads it with out errors
> 0/0: 300k DD 10 sectors of 512 bytes - G1:9 G2:17
> 0/1: Single sided
> 0/0: Single Step
> 800 sectors (800 data, 0 compressed, 0 unaval)
> Read complete
> Trying to write and it has errors from the get go.
> 0/0: 300k 10 sectors of 512 bytes
> :format error <0> overun
> :write error <2> no sector
> and on .............................
> written on a PC with 1.2 HD drive
> Tried on another 1.2 and on a 360k drive
> all capable of SD .
> I tried both HD and DD disks . all bulk erased first.
Don't use HD disks - as ImageDisk noted in it's initial
report, all sectors in the image are double-density.
You didn't show all the information, but since it's
single-sided, 10 sectors per track, and there are 800
sectors, this tells me it's an 80 track disk.
So - don't use a 360K drive (they are only 40 tracks).
You shouldn't need to worry about SD capability - there
are no SD sectors in the image.
The 300k data rate tells me that you recorded this on a
1.2M HD drive - I'm assuming you did not specify a 300-250k
data rate translation when you recorded it (?)
Assuming all that, it should write back to a 1.2M HD drive
with ImageDisk. It should also write back to a 80 track DD
drive such as TEAC-55F or SA-460 or TM-100-4. You would need
to set a 250->300k data rate translation to write on a DD drive.
I don't have any VAX disks to try, however I have read and
written Rainbow disks, which are also RX50 and use 80 tracks
by 10x512byte sectors, so I know ImageDisk works with this
10x512byte sectors can be twitchy on some PC setups. It
pushes the limits of the drive and formatting more than
the standard PC formats do. Most systems which use 10x512
have a more flexible FDC than the PC does.
- Clean the heads and make sure the drive is working OK.
Format a floppy on your PC, then read it with ImageDisk
and see if all sectors can be written.
** Don't bother looking at any other suggestions until your
** drive is verified to be operating 100%
- Make sure you are using a recent copy of ImageDisk (you
can get the latest from my site). Some of the older
versions had trouble with gap calculations, especially
on "tighter" disks.
- Try another PC (not just a different drive).
- Try making one of the Rainbow images from my site - this
is the same format.
NOTE: My images reflect the true data rate of the target
system (250k), so you will need to set a 250->300k
data rate translation to write them on an HD drive.
If this works, then there may be a problem with the
imaes you have created - send me one to look at.
- Check your drive speed. If it's high, try slowing it to
exactly 360 rpm - if it's "bang on", you might try slowing
it by 5-10 rpm - this can help if your PC is marginal at
the gaps required for 10x512.
- Look at the calculated gap sizes, and try reducing them
slightly. You shouldn't need to, but it's worth a try - PCs
are "highly variable".
I don't have VAX disks to try, but I've just successfully made
one of my Rainbow images using ImageDisk 1.14 and a HD drive.
The speed test shows my drive at 359 rpm.
If none of the above helps - send me one of your images and I
will see if I can recreate it.
PS: I've started writing an FAQ to send in response to numerous
emails I receive asking for help with ImageDisk - It's not
complete, and I need to tone parts of it down a bit (I was
a tad annoyed at yet-another-email-from-someone-who-didn't-
read-the-docs when I started it) - but it may be helpful:
- I just tried to make a disk with ImageDisk and I am getting errors.
- I just made this disk with ImageDisk, but it won't boot.
Q: Whats wrong?
A: Lots of things can go wrong (this is not an exact science).
ImageDisk is a very powerful and flexible tool, however this capability
comes at a price - you actually have to know a little bit about what
you are doing to make effective use of the tool. I've put the information
that you need to know in the ImageDisk documentation and help files, if
you really want to make disks that work, take the time to read it and
learn about the differences between floppy drives, data rates and the
compatibility issues involved. This is the best and most complete
answer to the above question.
I've been getting more and more mail from people who have obviously
"skipped" the documentation, tried to make disk which didn't work right
away, so the next step that comes to their mind is to contact me.
Please DO NOT ask me for help if you have not read the documentation!
Here are the most common problems that people encounter, and the
suggestions I have to offer:
- Drive type does not match that in which the image was recorded.
Most commonly occuring with 5.25" drives.
Use IMDU to determine the data rate at which the image was recorded.
If the disk was recorded at 250kbps and you are attempting to write
with a HD (1.2M) drive, you MUST set the 250->300kbps data rate
translation (also, see documentation regarding other compatibility
If the disk was recorded at 300kbps and you are attempting to write
with a DD (360k) drive, you MUST set the 300->250kbps data rate
NOTE: I try to record images on the actual drive type that is used
in a particular system - so 5.25" DD images are recorded on a 5.25"
DD drive at 250kbps. Most PCs of AT or later vintage with a 5.15"
drive will have a 1.2M HD (300kbps) type and data rate translation
will have to be used to recreate those images.
- PC is not capable of writing single-density.
Most PC floppy disk controllers are not capable of single-density
operation. Single-density formats have never been officially used
on the PC, and many manufacturers do not bother to include the
hardware necessary to support single-density operation.
Find another PC, or an add-in floppy card which does support
- Dirty heads / drive mechanics.
You finally got a disk image for your wunder-system from the 70's,
so you rooted around in your basement, and found an old DD drive
from an XT stuffed in under the bottom shelf. After blowing the bugs
and dust out of it, you connect it to your PC - and start making disks.
- Funny, they don't seem to be working.
Use good clean reliable drives - any drive thats been sitting for
"years" is likely to have collected dust and corrosion. This includes
the drives in your classic system! - Clean up the host drive(s) before
you try and make disks, and the system drive before you try and boot.
ImageDisk has plenty of features to help diagnose drive problems.
- Marginal disk format.
The PC uses a fairly inflexible floppy disk controller chip, which
cannot handle data as close to the index pulse as the controllers
in some non-PC systems. These system may pack extra data onto the
disk (for example, 10x512byte sectors resulting in 400k disks).
Some PC controllers can handle this better than others.
You may also be able to create the disk by slowing the drive
down by 5-10rpm, allowing extra time for the data to be written
before the next index pulse occurs. See the ImageDisk notes.
- Target system not working
Drives go bad, corrosion gets into sockets and connectors, and
the computer you are trying to boot may not be as reliable as
- Check to make sure the boot drive selects (light comes on) and
the motor/diskette spins when you try and boot the system. With
some drives, you may hear a click as the head loads. If this does
not happen, it's likely that your system isn't even running it's
- With the power-off and diskette removed, try manually positioning
the drive head out to the inside position of it's travel. When you
power the system on and attempt to boot, you should see the head
retract to track-0 (on a few systems, it goes to the middle of
it's travel). If it does not move, makes funny/unexpected noises,
or appears to move erraticly, clean and lubricate the drive
- If the above looks good, make sure you have the correct/proper
boot disk. To verify that the image was written correctly by
ImageDisk, try reading the newly written diskette into another
image file - then use IMDU to compare them, no differences in
the data area should be reported.
- Check your console connection - if it's integrated video, do
you have a blinking cursor on the screen. If it's a serial TTY
do you have it connected to the right port, and is it connected
properly. Use an RS-232 "light box" to confirm that RXD, TXD and
any control signals used are being correctly driven. Is the
terminal set to the right mode and baud rate.
- Most operating systems occupy more than one track of the boot
disk, so for MOST systems, when you boot, you will see the head
step out to the boot track, then it will step in one, two or
more tracks, usually pausing slightly on each one as it reads
the data from that track. On some systems, it will then seek
around the disk, reading system files, directory entries etc.
If you are seeing disk activity after the initial seek to the
boot track, this is a good sign that the system may be actually
- With the terminal disconnected, use a light-box, and note that
only ONE of RXD or TXD should be lit. Reconnect the termainal
and the other (RXD or TXD) should also light. Watch the light
that was on when only the computer was connected to see if it
flickesr during the boot process - this indicates that messages
are being sent to the terminal - check the terminal settings
and connections to determine why you are not seeing them.
- If you don't see RXD/TXD activity, try all the other ports
on the system - perhaps the boot disk assigns the console to
a different port than you expected.
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
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