Mission statement

Category: Uncategorised
Written by Administrator

This is RETROCMP, the site for restoration of classic computers.

This platform is dedicated to those people who try to get their old iron up and running. You finally found this nasty bug in your hardware after weeks of research? Send your story here!

We like to free you from the burden of maintaining an own web site. If you want to write something, create an account and let's get in contact.

It's just you and your machine that matters here!


You wonder what "RETROCMP" means? Read it as "Retro Computing", but, as you know, all real identifiers are just eight characters long.



How to write articles on RETROCMP

Category: Uncategorised
Written by Administrator

RETROCMP is open to everybody to write.

How to create an author account:

  1. You contact me and tell me that you want to submit an article.
  2.  I'll enable your account and setup a directory for your images.

How to write an article:

(Writing is easy and intuitive, even if the following step-by-step procedure contains some text.)

  1. Tell me what you want to write about. I'll generate the proper "category" for your article, see below.
    (Under Joomla, an "article" is displayed as one web page, so think of it as a short chapter. Many "articles" are grouped together by the "category", so the Joomla "category" is closer to a real life article than the Joomla "article" itself.)
  2. Login to retrocmp.com. In the USER MENU, click the "Submit article" button.
  3. There are four mandatory settings for your article:
    - choose a title. (Article URL is build fro mthe title, so be as specific as possible)
    - set the catagory, as discussed above. If you forget tha,m the article will vanish in Joomla's vaults.
    - set the online status. Must always be set to "Published".
    - set the access. "Public" means: article is online. "Registered" means: article is hidden, and only visible to you and some insiders.
  4. Enter text into the editor box. The editor is "JCE", here is documentation.

Save the first time! After save, press the "Edit" button to proceed writing. edit button

Attention: this is an online-system.
You will loose your work on any connection loss or session timeout.
So save your article often, at least every 10 minutes!

How to include images:

Your article live on images!

1.  Prepare your images: width must not exceed 600 pixels, format must be JPG or PNG.

2.  Before you can insert an image into the text, you must upload it. Click the "image" button BELOW the editor text window:
image button1
An upload form appears:

image upload form

The upper part lets you navigate to the directory on the server, were the image is to place. Choose "/stories/<your_name>". Under "Upload files" you select the prepared files on your local disk. ("Durchsuchen" is German and means "Browse")
Then click "Start Upload"

3.  After upload, you can insert the image into your text. Click the image button ABOVE the editor text window:

image button2

Select the image in the server directory (remember: it is "/stories/<yourname>"). Choose alignment, and press Insert.


Editing an existing article.

Just navigate to the article and press the "edit" button.

edit button


Category: Uncategorised
Written by Administrator

Anbieter, Webmaster und Verantwortlicher für den Seiteninhalt nach §§ 5, 6 TDG / § 6 MDStV:

Jörg Hoppe
Waldweg 12
37073 Göttingen


e-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

or This email address is being protected from spambots. You need JavaScript enabled to view it.


Telefon: 0551/488 88 89

Verantwortlichkeit für externe Links:

Der Webmaster dieser Seiten weist darauf hin, daß die Links zu externen Anbietern führen, sobald der Rahmen verlassen wird oder nicht ausdrücklich etwas anderes erklärt wird. Für den Inhalt der verlinkten Seiten sind die jeweiligen Autoren verantwortlich, der Webmaster übernimmt keine Verantwortung für die Richtigkeit bzw. Aktualität des Inhalts, für die Rechtmäßigkeit oder die Erfüllung von Urheberrechtsbestimmungen dieser Seiten. Insbesondere macht sich der Webmaster die fremden Inhalte nicht zueigen.

Der Webmaster haftet dem Nutzer nicht für die Richtigkeit die in dieser Domain enthaltenen Informationen oder Verweise. Eine Haftung für Schäden, die durch die Benutzung des Link-Katalogs entstehen könnten, wird nicht übernommen.

Der Webmaster distanziert sich ausdrücklich von eventuell rechtswidrigen Inhalten der verlinkten Seiten; der Webmaster bewertet den Inhalt dieser Seiten nur zum Zeitpunkt der Aufnahme in den Link-Katalog, eine spätere Änderung kann nicht überprüft werden.

Auch eine Marken- oder Urheberrechtsverletzung durch externe Anbieter ist dem Webmaster nicht bekannt. Sollten Sie dennoch eine Verletzung als gegeben ansehen, bitte ich um einen Hinweis kollegialiter und von kostenverursachenden Maßnahmen abzusehen.

Die private Nutzung dieser Seiten ist frei. Diese Linksammlung stellt im Sinne der derzeitige Rechtsprechung zumindest eine kleine Datenbank dar, welche nach §§ 87a ff. UrhG geschützt ist. Soweit Inhalte bzw. Datensätze aus dieser Domain in eigene Seiten eingestellt oder anderweitig reproduziert werden sollen, ist eine Erlaubnis des Webmasters erforderlich (welche i.d.R. erteilt wird).

Is there any good DEC RD53/Micropolis 1325 disk drive?

Category: Uncategorised
Written by Administrator

I have two PDP-11/53 in my collection.

The first one came with an RD53 drive, a 71 MB drive, wich was defective. luckily I could reformat it as RD52 with 31 MB capacity.

I’d like to get the 11/53 on the net, so I installed Ultrix11 onto the RD52. But too bad, despite Ultrix-11 has a TCP/IP stack, it is so buggy that it does not work. The newsgroups discuss this every year.

For the second 11/53 I bought an Seagate ST251 (40MB). This is DECs RD32. Ultrix-11 runs also OK here.

But the operating system of choice is 2.11 BSD, with TCP/IP. I installed this on my PDP-11/44 with great success.

But it does not fit onto the RD32 or RD52 disk. It needs a 70MB disk, a RD53.

So I went shopping at ebay.

EBay adventures

I could get an RD53 quite fast and quite cheap (it was announced without type designation, on request the seller told me it was a Micropolis 1325: bingo!).

When it arrive, I connected it and tested it with XXDP, the MSCP disk exerciser.

It was 100% OK! I put it aside, and wanted to install 2.11BSd later. (Lets call this drive “B”).

This deals was so easy, I decided to buy a second Micropolis 1325. I found another one, also not with type designation. The seller anounced an “ST504” drive from Micropolis. I made some statistics on the web and found, that almost all ST504 drives from Micropolis must be 1325 or 1335. So it was a blind buy. When the disk arrived, it was no ST504 disk: it was an ESDI drive /150 MB). The cable sets look the same, and the seller was not too exerienec, so he made wrong desription.

I tried to cancel the buy. The seller was quite friendly, but I agreed to a complicated deal: I had to ship the drive back, he would sell it again, and we would share old and new money 50:50. All this took 6 weeks to complete!

The RD53 error: spin up, spin down

After that I bought a 3rd (or “2nd”) drive on ebay. Lets call it “A”. As it arrived, it had an error:

It did spin up, but the sound became not steady. I heard the heads moving, but after 1 minute or so, the drive spun down again.

I got the good drive “B” from its shelf and connected it to my 11/53. But gues what? It had almost the same behaviour now! Spin up, some sounds, spin down. So it was OK, and after a few months it broke too.

I googled a lot after “repair micropolis 1325” and the like. There seem to be a lot of broken 1325’s out there, and all have this spin up, spin down behaviour. One guy wrote, he had 20 RD53 with this error in his basement!

There are tips about a stick rubber, wich glues the heads to its idle positions. Other people recommend putting the RD53 in a freezer and let them cool down, then power them up and never power them down.

Later I opened both RD53 to see whats real working on. Because it was winter and a rainy week, I vaccuumed my room frist and then let lot of dust-free december air into it. By the way, those 1980’s heads do not flight so low over the surface as on modern terabyte disks.

I found “A” and “B” have not the same error.

“A” seems not to get rotating fast enough: the spinning sound is modulating as the heads move from the inner to the outer track. So tracks are likely flying at all, and the motor seems to weak to get hte spindle up to speed .

I changed motor electronics with the other drive, notinh changed.

Drive “B” seems to get on correct speed. But here the heads are not moving, they are permanently set against the inner track.

Quick diagnostics: on drive “A”, the spindle bearings or the motor are weared out,on “B”, the head actuator had some problem.

Maybe in another live, I'd disassemble both drivers and mount the head+ actuator from “A” into the frame with the working spindle subsystem. Let’s save some money for a clean room!

So after all, I deald with four Micropolis drives, and got just one working for a few days.

A year later, while simplifying my live (again), I simply throw those both RD53 onto the local recycling yard. I never will buy them blind again!

The "Projects" section

Category: Uncategorised
Written by Administrator

These are descriptions of various hardware/software projects.

A playground for nerd-ness!


Show your wife where you really spend your time ....