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TU60 TA8E / M8331 maindec and caps-8 questions

Roland Huisman

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
Messages
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Location
The Netherlands
Hello, I've a few questions about the TU60, the TA8E controller and software.

Wednesday I can pickup a TU60 tape drive. I'm quite happy with that.
Since there is no controller with it I've made my own drawings for the TA8E controller.
The PCB is already drawn but I have some questions which I can't find in the documentation.

board.jpg

On the board are J1 and J2. All the pins with a signal are mentioned in the schematics.
But there is no info about which pins are on GND or floating.

Can anyone check these pins with the orange arrow for me on the controller if they are connected to GND or if they are floating?
And I assume that all the pins in the two orange rectangles are GND. Hope someone can check that for me too.

pin connections.jpg

I've asked David Gesswein about a DumpRest version for the TU60. It isn't currently available.
He said since the TU60 is supported in SIMH it can be added in the future and he put it on his to-do list.
But he can't say when it's done.

That brings me to the next point, are there TU60 images for Caps-8? And how can I put them on a tape?
Or did DEC supply a papertape tool to create a Caps-8 TU60 tape?

The last question... I found several Maindec files to test the controller and drive.
But I could not find the documentation belonging to those maindecs.
Is there a matching set for maindec and papertape image available?

Thanks in advance for your help!
Roland
 
As far as I understand OS/8 should be able to use TA8E / TU60 as a data device, not system device though.

There there are a CAPS-8 package on the SimH page: http://simh.trailing-edge.com/kits/caps8_all.zip

I think you should be able to move the file overs using serialdisk when running OS/8. But when it comes to CAPS-8 and all things related to TU60 I would ask Lou.
 
Very interesting!

I have a TU60 drive for my PDP-11/35 that I haven't restored yet. I would be very interesting to build this and test the drive. One more project to put on the stack...
 
MattisLind said:
As far as I understand OS/8 should be able to use TA8E / TU60 as a data device, not system device though. I think you should be able to move the file overs using serialdisk when running OS/8. But when it comes to CAPS-8 and all things related to TU60 I would ask Lou.
Click to expand...

Thanks, I've sent a message to Lou. I hope he can reply here. In the meanwhile I found this reverse
engineered documentation for a TA8E maindec. So the original documentation is probably a hard to find document.
http://dustyoldcomputers.com/pdp-common/reference/host/dhtaa.html
I've also seen those caps-8 files, but I'm not sure yet if I can make a bootable cassette with these files.

I've seen that the TU60 is supported in OS8 but only as a data device indeed. But there
are TU60 cassettes to create OS/8 bootable media on an RK05 for example.
So I really wonder how difficult it would be to let OS/8 boot from it as well...
It will be painfully slow but hey, it would be fun right? :D

There were a few people working on the OS8 diskimages for the serial disk server.
Maybe these guys can say anything about making the TU60 bootable for OS/8?

I've already added the TA8E bootstrap in the M847 extended edition firmware.
The bootstrap for CAPS-8 is the same as for the OS/8 installation cassettes.

anders_bzn said:
Very interesting! I have a TU60 drive for my PDP-11/35 that I haven't restored yet. I would be very interesting to build this and test the drive. One more project to put on the stack...
Click to expand...

Well, I will order 5 of these boards but I need only one. So that makes 4 spares which can go to other people.

I've checked the documentation from the TU60 and the pins are matching perfectly with the controller.
The GND and the not connected pins are also not mentioned in the TU60 documentation.
So when I have the drive I can check those connections on the drive as well... When they are open in
the drive they can be open on the controller. And when they are GND the controller can be GND as well...
 
Last edited:
Roland Huisman said:
I've seen that the TU60 is supported in OS8 but only as a data device indeed. But there
are TU60 cassettes to create OS/8 bootable media on an RK05 for example.
So I really wonder how difficult it would be to let OS/8 boot from it as well...
It will be painfully slow but hey, it would be fun right? :D

There were a few people working on the OS8 diskimages for the serial disk server.
Maybe these guys can say anything about making the TU60 bootable for OS/8?
Click to expand...
I haven't yet seen the driver for the TU60, but it seems likely that it is not small, which means it will be difficult to come up with an OS/8 system driver.
I've checked the documentation from the TU60 and the pins are matching perfectly with the controller.
The GND and the not connected pins are also not mentioned in the TU60 documentation.
So when I have the drive I can check those connections on the drive as well... When they are open in
the drive they can be open on the controller. And when they are GND the controller can be GND as well...
Click to expand...

I found this
tu60gnd.jpg
in the TU60 drive doc's.

Vince
 
Hi Vince,

vrs42 said:
I found this
View attachment 55102
in the TU60 drive doc's.
Click to expand...

Ah great! I didn't see that. I did see that the TU60 cables are crossed in that document.
Totally overlooked that piece. Thanks!

vrs42 said:
I haven't yet seen the driver for the TU60, but it seems likely that it is not small, which means it will be difficult to come up with an OS/8 system driver.
Click to expand...

Ah okay that's a shame. I was hoping that it would be a small step since the drive is already supported in OS/8.
But still enough fun to use it with OS/8 and Caps-8. :D

Regards, Roland
 
A difficulty with the TU60 is to find tapes that work with it and tapes that last. The original tape had this special notch and also a blank leader. Then the tape itself was quite sturdy. I tested some more modern tape and it took just one rewind to destroy the tape.

Right now there is one single tape on Ebay in Italy. This type of tape I have tested and it worked quite well. It is also longer than the standard DEC TU60 tape so it will be able to store more (if that matters).

https://www.ebay.com/itm/VERBATIM-DATA-CASSETTE/233186791756?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
 
Folks,

Sorry for being offline for so long. We've been working on our move from the NYC area to the Washington DC area.

Indeed Mattis is correct that OS/8 works with the TA8E/TU60 as a non-system device. However, that is not a problem for making a CAPS-8 system cassette. To use OS/8 to make a CAPS-8 bootable cassette, one does not use BUILD as they are used to. Instead, you simply copy the files to a cassette that has first been ZEROed. Your OS/8 system head should of course have the TA8E handler INSERTed, or I think one can use MCPIP (I did the former.)

The sequence of the files to be put on the cassette to make it bootable is critical. The first file must be the secondary loader, then second is the monitor. The remaining file order is not important. The TA8E bootstrap (either the one fat-fingered/MI8E'd into memor or the OS/8 BOOT TA) will read the secondary loader in to memory, which will proceed to load the monitor in off the cassette.

It is important that cassettes used have clear leaders and have a hole/notch in the top approriate for a datacassette. Most of my original DEC TU60K media is unreliable, however I have had some success with more modern cassettes. I saved the clear leaders and housings from old cassettes and re-packed them with new tape. I found BASF (pre-EMTEC spinoff) tape to be the most reliable, however, even some recent Memorex tape was OK.

And here is my post to alt.sys.pdp8 from 13 years ago when I first got CAPS-8 running again : https://alt.sys.pdp8.narkive.com/2udVI790/caps-8-revived-on-original-iron. You will see that I built the bootable cassette the hard way. Back then I had very little hardware and no OS/8.

In a fit of insanity some years back, I tried "playing" a TU60 datacassette in an audio cassette deck and digitizing the audio. At an 11kHz sampling rate (monaural, of course), I converted the audio to a raw data file. I made a crazy Excel spreadsheet that could process one block of data at a time, decoding the audio file, using the writeups in the manuals. It read the header and even verified the checksum. If there was tape dropout, you could look at the plot of the audio file and recover the bits by eye. It really did work and could handle the fact that "playback" of a Philips Compact Cassette used for audio has a constant 1-7/8 IPS tape speed while the TU60 which has no capstan, moves at varying tape speed (and therefore bit rate) depending on how much tape is on the the takeup reel. I made it while preparing to recover CAPS-11 Basic source tapes (which we recovered OK on the real hardware!) I will look for this file in the coming weeks and send it to anyone who is intersted. Recall that I am a mechanical engineer, so some things are brute force.

Lou
 
Last edited:
Hi Lou,

Lou - N2MIY said:
To use OS/8 to make a CAPS-8 bootable cassette, one does not use BUILD as they are used to. Instead, you simply copy the files to a cassette that has first been ZEROed.
Click to expand...

Thanks a lot for your info! That sounds quite easy to do. But I still think it would be very nice
to have a DumpRest version for the TU60 too. You never know what interesting kinds of tapes show up in the future.

Lou - N2MIY said:
Your OS/8 system head should of course have the TA8E handler INSERTed, or I think one can use MCPIP
Click to expand...

That was one of my questions in general. How to add devices in an existing system. Not only the TU60, but also the TU56, RX01 etc...
I hope someone can point me into the right direction on that...

Lou - N2MIY said:
The sequence of the files to be put on the cassette to make it bootable is critical. The first file must be the secondary loader, then second is the monitor. The remaining file order is not important.
Click to expand...

Are these files on the http://simh.trailing-edge.com/kits/caps8_all.zip file usable on real tape?
I wonder which files I need to put on the tape. What are the filenames of the secondary loader and from the monitor?

Thanks for your help here!

Regards, Roland
 
Today I got my TA8E boards and I have build one of them.
And I got it trough the static maindec test :D:D:D

IMG_20190823_013206.jpg IMG_20190823_013215.jpg

But at first I got a lot of errors of the A register. It turned out to be a bad 74179.
And then I got these errors continue looping...

PC=0312 KSEN SKIPPED
PC=0322 KSAF SKIPPED

Since there is no original maindec documentation I could not exactly find
where 0312 and 0322 were in the code. But thanks to the work of R.Krten I
could figure out that these errors were generated at IOT 2 and IOT 5.
And in the code was mentioned that these tests were skipped in case of an error.

The errors were coming from the circuit which checks for an empty drive, write lock etc...
Then I found two typo errors in my schematic. A label was called EOT-BOT_H and at another place EOT_BOT_H.
And the second was CRC-BLK_ERR_H instead of CRC_BLK_ERR_H. So I got two pins floating in my design. :(:(:(
Normally I always copy labels to prevent these kind of errors. So I don't know why this went wrong...

IMG_20190823_013337.jpg

But hey, DEC used more wires on their original TA8E board. ;) I will update the schematic drawing and PCB files off course.
I don't like wires on my PCB. But I think it's very nice that I got this far. Before I can go further I need the rollers
to be done first. I think I will sent them out to a factory like Terry's Rubber Rollers & Wheels

I will put the schematic on my GitHub. PCB files will come later when I have updated them.

In the meanwhile I'm going to focus on building a few VC8E clones and the M882 RTC.

Regards, Roland
 
From both of the TU60 drives which I have here just one sensor light bulb was still working.
I could not find the spec of the bulb in the documentation or about the HEI B10461A sensor.

So I've done some measurements. The 'bulb ok' detector circuit takes about 1V of the 5V power.
Dec often seems to use a bit lower voltage on bulbs to extend their lifetime. So I assumed the
bulb would be a 5v or 6v model with a quite high power. The current that flows trough the bulb was
around 100mA at 4V. So that would mean that I need a bulb of approximately 120mA at 5V or 150mA at 6V.

After a bit of searching it seems to be a wire leaded T1 (3mm) bulb. I found a 5V 115mA model 715 incandescent lamp at Farnell.
https://nl.farnell.com/cml-innovative-technologies/715/lamp-wireended-t1-5v-0-575w/dp/1139298

The sensor was quite easy to open. Now all sensors have new bulbs in it. They give the exact same
brightness as the original. And the sensor output has also the exact same voltage levels.
So that is done as well... Now back to the idler tires...

TU60 old lamp out.jpg

TU60 new lamp in.jpg

IMG_20190826_213531.jpg

To be continued...

Regards, Roland
 
Roland,

send me th exact dimensions you need for the roller, I will 3D print some for you.
The ninjaflex flexible filament should be just right for the job.

Jos
 
Hi Jos,

Sounds like a nice experiment to me! The inner diameter is 35mm, outer diameter is 38.2mm and the height is 6mm.
Probably a good idea to make the inner diameter 34.9 for a tight fit... Do you know if it's possible to glue the printed
rubber on a surface? This to prevent slipping of the aluminum wheel.

Thanks for your help!

Regards, Roland
 
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