Close

Jack in the Box

A project log for THE PERTEC WHISPERER-MAINFRAME TAPE DRIVE EMULATOR

A.K.A. THE 9 TRACK TAPE DRIVE COMMUNICATOR Talking to Mainframes Era Reel to Reel 9 track tape drives

[skaarj][skaarj] 03/26/2019 at 20:291 Comment

As a result of my witchcraft activity, the new experimental whispering spell needs a place to enclose its powers while performing its magic. It also needs a screen and some buttons to have fun with.

Of course the back side of the leds and buttons must not overlap the peripheral boards.

I tried many arrangements and the last one (bottom) is the final design.

Some words are in Romanian because the ancient tongue spoken by many warriors and vampires has strong magic powers especially when swearing, and spell radius&effect increase when the finest of the finest beers arrive at the local shop.

From top-left to right:

L is LED,  K is button. 

Online, File Protect, Load/Eject, READ/WRITE, the "K4P" means button with 4 positions which selects the functions.

Bottom leds:

Functions: Host mode, Drive mode, Monitor mode, the "spare" is now Bypass mode and the last button (K) on the right is no longer connected, just like the button above K4P.

Right side of the screen:  top - power-on LED,  bottom - on/off switch.

Not bad for a manually processed 4U rack-mounted enclosure. The brackets are not installed yet.

Both mainframe and tape drive need two connectors. This is the Pertec interface: the greatest pain of the PDP-era. There is no acknowledgement between the host and the drive. The data is just.... "roared" through the bus and the circus training is performed using status and control line jugglery.  On software side there's a lot of logic operations - a great exercise for the neurons.

Pictures from inside:

from left to right:

ATX PSU,  STM32F4 CPU board, CPU interface to buffer (has 4 x IDC40 connectors on top),  CPU Buffer, Bus interceptor (4 x IDC40 on top), rambuff+comms, mainframe buffer, tape drive buffer.

Display via an old POS 2x20 VFD with 9600 baud serial line.

The edge-mounted IDC40M connectors helps me watch the magic flow using the HP1662 logic analyzer.

TISO:   tape isolate;   CISO:  controller (mainframe) isolate.

/RSS-DIR:  Read-StatuS direction - it changes between host and drive mode;

WCA-DIR:  Write-Control-Address direction - also changes like above.

Close-up view of uSD card module, the MAX232 and the RJ45 serial VFD connector

There is a second RJ45F on the board. The second VFD is used as a debug console when I am too lazy to connect the serial line to another PC.

Close view of the micro controller i/o buffer. This is bidirectional and it also serves as a 5V to 3.3V level shifter.

Status leds. From left to right:  

mainframe_isolate, rss_dir, wca_dir, tiso, ciso, 3v3, 5V, 12V.

 This is the pertec interface interceptor from the controller (mainframe) side of the Whisperer.  In the back side there are two card-edge-50 connectors, that's the input. The J1 and J2 outputs go to the 'mainframe' connector shown in the 5th picture.

You can also notice the 4 x IDC40M connectors. With them I can inspect the traffic using the HP1662 analyzer at input, inside the system and there is also another pertec interceptor at the output. This way I can trace any operation failures. 

Party time!

The analyzer pods are shown here. Whatever line is up, it means logic 1. Down is logic 0. 

The Pertec interface use inverted logic, meaning a drop of voltage means true.... and from now on it is extremely important what kind of beer I chose in order to see the true data in the inverted flow.

This old beast has a beautiful manual with a lot of pages showing the complex operations for programming whatever I want to analyze. 

This has not been seen for decades - the actual flow of a Pertec interface data transfer.

W0......W7 lines during a "tar -cvf /dev/nsa0 /etc" operation. 

"nsa0" was achieved under FreeBSD 11.3 and an old Pertec to SCSI converter from Qualstar.

This is the place where tie magic happens.

[END OF TRANSMISSION]

Discussions

Ken Yap wrote 03/26/2019 at 23:38 point

Thanks for the interesting account and pictures. Enjoy your beer!

  Are you sure? yes | no