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PDP11 - RX01 Writing disks

S

spiceminer

Experienced Member
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Mar 8, 2014
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Dear All,

as the RX01 cannot format disks, the PDP11GUI is not helpful writing disk images without pre-formatted disks, correct?

So I need to make another 8" Floppy Disk Drive work with a PC/Image Disk/FM compatible controller, right?

About the media, I suppose any single sided media will work (double or single density)?

Can I write Single Sided Media for the RX01 with a double sided/double density drive on the PC (I think there might be a problem with the index hole position, right?)

Thanks a lot for your help
Regards
Stephan
 
I believe the RX01 is "standard" IBM 3740 format, aka SSSD, FM encoding, 128 byte/sec, 26 sectors per track. If you have the ability to electrically interface an 8" drive to a PC it should be straightforward to LLF a diskette.
 
The only time I needed to do a LLF on RX01 media (IBM 3740) was either 1) I was low on media and recycled a few with minor defects or 2) was dealing with double sided variants (index hole differences be here). Most third party drives and Qbus controllers can do this by just toggling in a few (proprietary) bits into the control registers via ODT. See https://www.ebay.com/itm/266410525120 No experience with doing this from a PC or what software you would need.
 
spiceminer said:
@wa2flq : Did I understand correctly, a fresh SS/SD Media will not need LLF to be used on the RX01?
Click to expand...
All the media I purchased as RX01 floppies was formatted. If someone taken a magnet to it (and it is harder than you think), a LLF may be necessary. An RX02 drive could convert the RX01 media to the RX02 format. But anyone who used an RX01, simply purchased it as already low level formatted. You didn't have any other option.
 
All of the RX01 disks I've ever seen have been single-sided. If you have a box of DS disks, it would seem that you need to add an index hole in the right spot.
Of course, you can low-level format RX01s on a PC with a controller that supports FM encoding.
 
spiceminer said:
I only have one pack of 10 SSDS 8" fresh never used disks, so I will need LLF .... what is the less time consuming way forward? Set up another non RX01 8" Drive with Image Disk and write one of these http://dunfield.classiccmp.org//img42841/d/pdprt11.zip
Click to expand...
I don't quite follow what media you have that requires a LLF. The following designations and products were common
  • SSSD => Single-Sided Single-Density (RX01)
  • SSDD => Single-Sided Double-Density (RX02)
  • DSSD => Double-Sided Single-Density
  • DSDD => Double-Sided Double-Density
Many third party Qbus controllers can do, with different success rates, media coatings* and the right index hole locations, do a conversion between the types. OS support varied as well. but RT-11 handlers or patches are common. Of course you need to do higher level format of a valid OS directory structure to usable, but that is a different task.

Apologies, if I missed something.

* Third party media was often coated on both sides even when sold as Single Sided. Double Sided 8 inch floppies were (RX03) never released by DEC.
The third party releases where mostly, but not always compatible.

Jerry
 
May I kindly ask if somebody could provide me a SIMH compatible 8" single sided 256kb RX01 disk image that is bootable? The kind of software does not matter, it is just to check that my setup and diskettes are fine. I intend to use PDP11GUI to write a disk image to a diskette that is already IBM preformatted.
Thanks!
 
Thank you @AK6DN - It looks like I have some issues with my RX01s.

From "Unit 0" (left drive) I get errors from the first sector.

With "Unit 1"(right drive) I can write the image until 85% then I get errors until the last sector.

The drives have been disassembled and completely cleaned, so dirt or old grease could not be the issue.

Do you know if I can boot from Unit 1 or does this only work from Unit 0
 
spiceminer said:
Do you know if I can boot from Unit 1 or does this only work from Unit 0
Click to expand...

I don't know exactly what PDP-11 and boot mechanism you are using, but generally speaking the answer is yes.
For example, on a unibus PDP-11 with the M9312 DX bootstrap prom, you can enter either DX0 or DX1 at the prompt to select the boot unit.
 
You should be able to boot from Unit 1 - with the proviso that your bootstrap supports it. Or type in a bootstrap that does.

Dave
 
Dear @daver2 !

I do have a ROM card from which I asume it is a bootstrap card. With the card installed, I cannot see any change in behavior of the ODT....

1712520301694.png


Do you maybe have a link to a bootstrap that supports booting from Unit 1 that I can key in from ODT for testing purpose?

Thanks and best regards
Stephan
 

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