Entrex 480 Data/Scope

Saturday, January 4, 2025

More MERA 9150 hardware & manual resources found!

System MERA 9150 Podręcznik Serwisowy Cz. 2

Wibryssy — 11/21/2025 4:31 AM

We found and scanned part 1 of the service manual. Unfortunately, it appears to be for the Nova 1200, not the MERA 9150 manufactured at MERAMAT.

System MERA 9150 Podręcznik Serwisowy Cz. 1

Wibryssy — 11/23/2025 4:55 PM

I analyzed 9150 CPU board and i think that is adaptation of the Nova 2. Main difference is that the Polish board doesn't have any PROMs. All addressing and function selection are implemented using standard TTL logic.

Monday, March 25, 2024

How the Entrex 480 / Nixdorf 620 Boots

Reference decoded tapes verbose files on GitHub Forgotten Machines

March 24, 2024 From Bruce Ray with Wild Hare Computer Systems / NovasAreForever.org:

The standard DG/DCC Data Channel device [DCH] tape/disk bootstrap program consists of only 3 instructions:

375/ 062677 IORST

376/ 0601<xx> NIOS <device code>

377/ 000377 JMP

This is the program initiated by the PL switch on the 'standard' machines

DCH device controllers are designed to boot from record/sector zero of a tape/disk drive into location 0 onward, and therefore overwrites the JMP . instruction at location 377. Any standard bootable DG/DCC tape/disk [and I would assume Entrex] successfully uses this model. If a faithful image of a tape/disk is created and appropriately configured in an emulator, the system should be 'bootable'. A correct SimH-compatible tape restoration works on all of the very-diverse systems I work with, and likewise for disk images and appropriate disk emulation configuration.

Therefore, if a known "bootable" tape is accurately recovered to SimH-compatible format, the resulting contents should behave exactly like the original hardware if the various parameters are met. This is the basic approach successfully used over the decades for handling even the 'weirdest' client situation.

Once the controller is started [i.e. NIOS <device>] the controller will transfer words from the device to main memory automatically. Even if an extreme custom hardware modification were made to the front console's program load logic, the examination of the tape/disk record/sector zero might reveal more information, faster, than trying to grok custom hardware modifications. Knowing the exact [human] operator procedure to bootstrap the system would reinforce

the decision to attack the problem either bottom-down or bottom-up. Top-down In this case would be to start with a known good accurate copy of the tape/disk media in question, bottom-up would be dissecting schematics to discern the forest from the trees...

---------------------------------------------------------------------------------------

We provided Bruce with these two recovered SimH-format 9-track tape files:

Entrex_Nixdorf_620_Save_PRIX_22-01-87.tap

Entrex_Nixdorf_620_Master_Didos_1_genere_08-10-83.tap

to which Bruce replied with these glorious preliminary results:

Mera 7951 OM Terminal listed on eBay in Buk, Poland

I've never seen one of these come up for sale on ebay, and yet, since March 2024, it has been listed, on and off.

It is now March 14, 2025, so it has been listed for one year without being sold.

2,100.00 PLN ~= $550 USD as of now

Current Auction Auction Archive

Seller waavia

Description translated to English:

Rarity

Condition as shown in photos

Personal collection preferred

Shipping within Poland 70 zł

Original Polish Description:

Rarytas

Stan jak na zdjęciach

Preferowany odbiór osobisty

Wysyłka na terenie Polska 70 zł

Thursday, March 14, 2024

Nine-Track (9-track) 800bpi NRZI Format decoding

I really appreciate the confirmation of 0x13, because the ANSI documentation you shared is "clear as mud" on this topic for me. I don't know how this description translates to 0x13, BUT, I AM seeing 0x13 twice at the end of my tapes, so your real-world description overrides my confusion from this ANSI document.

I had no idea how `1 bits in tracks 2, 3 and 8` translates into binary `00010011`. tracks 2, 3, and 6, maybe if you start counting backwards where Parity is track 1, but not 2, 3 and 8....No matter how I arranged it, I got a totally different value from this.

You know, in typing that last message out, I think I just figured out why that ANSI document was SO confusing to me...they renumbered all of the tracks with their own 1-9 numbering system, starting from one of the tape edges, and never really gave a diagram like this saying how their numbering system "maps" to the real-life track names. I guess for ANSI documents, they need to add this additional layer of obfuscation to make their attorneys happy? Anyway, I think I'm getting it through my thick head now. If I take their diagram and re-draw it like this:

Yeah, I see it now...from left to right

00010011 - 0x13 "TapeMark"
01234567P - real world tracks
765391824 - ANSI track order

OK, 3, 8 & 2, or 2,3 & 8... got it now! Anyway, the main point of my message was to say "Thank YOU" on this, and I know I went a bit overboard.

I really should put these last 2 messages into one of my blog posts. It could help the next less-technical person like myself who dares enter this territory...

-------------------------------------------------------------------------------

SimH .tap files:

larsbrinkhoff — March 14, 2024 at 2:50 AM

Your entire .tap should look like this:

17 of these: "FC 0F 00 00" <4092 bytes> "FC 0F 00 00"

(FC 0F 00 00 is little endian for 0xFFc which is 4092 in decimal)

1065 of these: "3C 0F 00 00" <3900 bytes> "3C 0F 00 00"

End of tape: "00 00 00 00 00 00 00 00"

-------------------------------------------------------------------------------

Link to my Lotus Notes database program decoding this:

Tuesday, March 12, 2024

Pertec 9-track Formatter "Key To Tape" device

This device is NOT part of the Entrex 480 system,

but in order to understand a "Key-To-Disk" system like the Entrex 480,

here is a "Key-To-Tape" stand-alone device to illustrate the differences.

Notice the "029" keyboard layout?

Acquired from Orrill's Auctions, Los Angeles on March 12, 2024

IBM 029 Keypunch Keyboard vs Entrex Data/Scope

Compare this keyboard to the "029" keyboard option for the Entrex Data/Scopes (Keystations). As the Entrex 480 advertisements state, this keyboard layout was a featured option on the Entrex Keystations so that operators who were used to the IBM 029 keypunch keyboard layout were able to transition to using the Entrex Data/Scope without any re-training on the keyboard layout. How cool was that?!

Entrex 480 / Nixdordf 620 System Operation Exploration (a list of screen menu options)

Recorded near Brussels Belgium November 2021:

See Full Playlist

And THIS is the tape that booted this system!

Original Early 1970s USA Entrex 480 Chassis Card Slots

This chassis was from the July 2020 Frenchtown, NJ Auction

Digital Commputer Controls

Model No. D-116B

Serial No. 0293

Monday, December 25, 2023

Mera Christmass...

2023 Mera Xmas!

2022

So well done...
from MHKI's Facebook Post

Mera Christmas!

Snake from IKEA

Saturday, November 11, 2023

Alan Warren's "in-desk" Entrex Data/Scope with DEC VT-05 and PDP-11 home setup

https://www.facebook.com/groups/40651613978/permalink/10161269378003979

UPDATE: Unfortunately, the above-linked post has been deleted or removed, but thankfully, we archived it, along with all comments, on November 13, 2023. To see that archive, click here.

posted by Alan Warren

https://www.facebook.com/groups/40651613978/user/1748734285

It should be noted that the PDP-11 is mounted into an Entrex 480/Nixdorf 620 Rack Chassis, so this is a "PDP Retrofit" into an Entrex 480 system chassis!

The data scope is in its original desk and the pdp is mounted in an Entrex cabinet. The entrex stuff was given away over 40 years ago I am sad to say.

- Alan Warren

Too bad that all of this was likely scrapped many decades ago...but we thank Alan for the vintage picture!!!

A Forgotten Machines T-shirt visits the MHKI and the Mera 7951 in Katowice

These pics were taken by my friend Kris on his visit today to the Muzeum Historii Komputerów i Informatyki (Museum of the History of Computers and Information Technology) in Katowice, Poland.

What an honor it was to see him there, wearing our branded T-shirt! I cannot wait for the time to come for me to visit this wonderful place myself!

Wednesday, September 20, 2023

Forgotten Machines at VCFMW 2023! Entrex Data/Scope, Entrex Trapezoid Data/Terminal and Mera 7951 and More!!!

Photo credit goes to CommodoreZ at https://commodorez.com/

https://www.commodorez.com/VCFMW18/76.html

https://www.commodorez.com/VCFMW18/10.html

https://www.commodorez.com/VCFSW2023/117.html

Entrex (Nixdorf) Trapezoid Data/Terminal spotted in The Love Boat Season 1 Episode 20 (1978)

IT IS THE LOVE COMPUTER FROM THE LOVE BOAT!!

See reddit thread here

Thanks to SomePeopleCallMeJJ for finding this!

https://www.youtube.com/watch?v=cKlwJi7q9EI&t=576s

https://www.youtube.com/watch?v=cKlwJi7q9EI&t=370s

You can actually see the Nixdorf badge pasted right over where the Entrex logo silkscreen would have been in the lower left of the plexiglass on the screen