Purchased an MDS-120 with goodies

[Royce Taft]

Hi all,

I’m Royce, and I’m new to the group.

I stumbled upon an eBay listing for what the seller claimed to be an Intel MDS-120, and sure enough a pic of the nameplate confirms that part number. I can’t find documentation that proves this machine existed—at least not in the public. There are Intel property/asset tags on all contents in the lot, so I am led to believe that this system was used by Intel in-house. 

I thought some members of the group may find this intriguing and can possibly shed some light on it. My present goal, upon receipt of the system from Tucson, is to test and repair the components of the system to restore it to working order. Although no documentation was included in the lot, I intend to document (via pictures, videos, and/or written words) this model to the best of my abilities. I’m counting on the schematics for the MDS-220 being similar enough to be useful. I plan to dump all ROMs and share them with the group if they appear to be a version not previously captured. 

Here’s a link to the completed auction:

Following the link, click “see original listing” to view the photos. 

I imagine the link will expire in the future, so here’s an internet archive link:

The goodies are the MDS-730 external dual double density floppy disk drive unit, Prompt 48 programmer, and MDS-201 expansion. 

In the item description, the seller mentions seeing two cards in the MDS-120 but was afraid of damaging the unit by pulling off the front cover, so the cards remain unidentified until I receive it. Anyone want to take any guesses on what they might be? To be honest, I’m a little worried that there are only two cards. I would have expected more given the number of peripherals. I’m also a little disappointed that the expansion unit contains no cards. 

However, I’m very excited to dive into the realm of vintage Intel microprocessor development systems.  I have an HP 64000 that has been a blast learning about (I’ve got a relatively short clip on YouTube demonstrating it emulating a 6809 in a short loop of NOPs). There’s something so fascinating to me about the tools and processes used by engineers in the early days of microcomputers to develop hardware and software which are accomplished today via much easier and quicker means. To do so much with so little. 

I will post updates here in this thread—if the group is okay with that. 

I’m eagerly awaiting the delivery, expected in a couple of weeks. I was actually intending on saving the cost of shipping and doing local pickup, but the price of fuel, the heat wave hitting the area, and my pregnant wife saying NO WAY to a 28 hour (round trip) road trip coming from Northern California led me to just pay for shipping and stay home. Fingers crossed it all survives shipping! 

-Royce Taft

[roger arrick]

Hello Royce, 

I have talked to this seller.
Yes this is a standard MDS II system with dual external floppy drives that connect to a FDC board set in the CPU card cage,

along with an integrated FDC for the internal single density drive.

There's also an expansion chassis but I don't know what's in it.

This system has the single-density board set in it but he doesn't want to split up the system.

If you get it, and you want to trade for double-density, let me know.

--  Roger Arrick -- Tyler, Texas, USA -- Ro...@Arrick.com --

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From: intel-...@googlegroups.com <intel-...@googlegroups.com> on behalf of Royce Taft <royc...@gmail.com>
Sent: Saturday, July 1, 2023 10:59 AM
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Subject: intel-devsys Purchased an MDS-120 with goodies

 

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[roger arrick]

By the way everyone, there is an FB group for intel development systems too:

https://www.facebook.com/groups/1929894570383916

Log in or sign up to view See posts, photos and more on Facebook. www.facebook.com

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From: intel-...@googlegroups.com <intel-...@googlegroups.com> on behalf of roger arrick <ro...@arrick.com>
Sent: Saturday, July 1, 2023 11:53 AM
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Subject: Re: intel-devsys Purchased an MDS-120 with goodies

 

To view this discussion on the web visit https://groups.google.com/d/msgid/intel-devsys/DM6PR14MB34492629FD1464A716444BDFD82BA%40DM6PR14MB3449.namprd14.prod.outlook.com.

[Al Kossow]

On 7/1/23 9:54 AM, roger arrick wrote:
> By the way everyone, there is an FB group

Meta is offensive. I know too many people who quit from there.
AVOID

[Royce Taft]

Hi Roger,

If what you say regarding the boards in the CPU card cage is true, I will likely want to trade as I’d have no use for a SD board set.

After I receive the lot, I’ll get back to you on that. 

And thanks for the link; I’ll check out the FB group. However, I’m not very active on Facebook or other social media platforms, but I do browse sometimes. 

Thanks again,

Royce

On Jul 1, 2023, at 09:53, roger arrick <ro...@arrick.com> wrote:



[William Beech, NJ7P]

Royce,

Welcome to the group.  I'm Bill, and I maintain a Web server with the Intel Manuals and my experiences in bringing these old systems back up  - www.nj7p.org.  Good luck with your restoration.

Bill

[Royce Taft]

Bill,

Thank you for the warm welcome.

It looks like you provide quite a great service hosting that information. I will definitely appreciate your site as a resource. 

Royce

On Jul 1, 2023, at 11:21, William Beech, NJ7P <nj...@nj7p.info> wrote:



Royce,

Welcome to the group.  I'm Bill, and I maintain a Web server with the Intel Manuals and my experiences in bringing these old systems back up  - www.nj7p.org.  Good luck with your restoration.

Bill

On 7/1/2023 8:59 AM, Royce Taft wrote:

Hi all,

I’m Royce, and I’m new to the group.

I stumbled upon an eBay listing for what the seller claimed to be an Intel MDS-120, and sure enough a pic of the nameplate confirms that part number. I can’t find documentation that proves this machine existed—at least not in the public. There are Intel property/asset tags on all contents in the lot, so I am led to believe that this system was used by Intel in-house. 

I thought some members of the group may find this intriguing and can possibly shed some light on it. My present goal, upon receipt of the system from Tucson, is to test and repair the components of the system to restore it to working order. Although no documentation was included in the lot, I intend to document (via pictures, videos, and/or written words) this model to the best of my abilities. I’m counting on the schematics for the MDS-220 being similar enough to be useful. I plan to dump all ROMs and share them with the group if they appear to be a version not previously captured. 

Here’s a link to the completed auction:

Following the link, click “see original listing” to view the photos. 

I imagine the link will expire in the future, so here’s an internet archive link:

The goodies are the MDS-730 external dual double density floppy disk drive unit, Prompt 48 programmer, and MDS-201 expansion. 

In the item description, the seller mentions seeing two cards in the MDS-120 but was afraid of damaging the unit by pulling off the front cover, so the cards remain unidentified until I receive it. Anyone want to take any guesses on what they might be? To be honest, I’m a little worried that there are only two cards. I would have expected more given the number of peripherals. I’m also a little disappointed that the expansion unit contains no cards. 

However, I’m very excited to dive into the realm of vintage Intel microprocessor development systems.  I have an HP 64000 that has been a blast learning about (I’ve got a relatively short clip on YouTube demonstrating it emulating a 6809 in a short loop of NOPs). There’s something so fascinating to me about the tools and processes used by engineers in the early days of microcomputers to develop hardware and software which are accomplished today via much easier and quicker means. To do so much with so little. 

I will post updates here in this thread—if the group is okay with that. 

I’m eagerly awaiting the delivery, expected in a couple of weeks. I was actually intending on saving the cost of shipping and doing local pickup, but the price of fuel, the heat wave hitting the area, and my pregnant wife saying NO WAY to a 28 hour (round trip) road trip coming from Northern California led me to just pay for shipping and stay home. Fingers crossed it all survives shipping! 

-Royce Taft

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[Jon Hales]

Hello Royce

Welcome to the group and congratulations on your MDS system.

I'm writing to comment on earlier discussion, particularly the evidence of the cable shown in several of the photos. The 'standard' floppy cabling runs from the controller to a pair of 37-way connectors on the backplate. That arrangement could support up to four external drives. Your system has a variant, where there is one backplate connector and the other branch of the cable runs directly to the internal Shugart. This arrangement means the internal drive handles double density (M2FM encoded) media, which makes all the drives consistent. 

The photo showing the solder side of the backplane appears to indicate a two-slot inter-connect in the lowest position - this suggests your system does include a floppy controller. The cable mentioned above suggests it is likely to be the iSBC-202 double-density type with a pair of PCBs.

The 'standard' arrangement involved a short 50-way cable from the IOC (the large PCB set vertically at the back of the chassis) to the Shugart which was single-density (FM encoded). Single density has the advantage that it is easy to read and write disks for the MDS with more modern PCs (which isn't the case for M2FM, although work-arounds exist).

You are likely to find that the cable to attach the external drives to the 37-way connector on the backplate is missing. The wiring is detailed in the schematic drawings, but having tried this, it isn't simple.

Best regards

Jon Hales, UK

[roger arrick]

Jon's observations are correct and the bus-mounted FDC board set would need to be double density in order to justify this special cable that connects to the internal drive which typically connects it to the integrated single density controller.  If the bus-mounted FDC board set was single density there would be no reason to do this.  

But, it still could have been changed out later I suppose.

--  Roger Arrick -- Tyler, Texas, USA -- Ro...@Arrick.com --

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From: intel-...@googlegroups.com <intel-...@googlegroups.com> on behalf of Jon Hales <jonh...@gmail.com>
Sent: Sunday, July 2, 2023 6:29 AM

To: intel-...@googlegroups.com <intel-...@googlegroups.com>
Subject: Re: intel-devsys Purchased an MDS-120 with goodies

To view this discussion on the web visit https://groups.google.com/d/msgid/intel-devsys/CANPXPJn83Gjz%2B4WkiJVdVC4AAtYuEZzK8YrZ37VEaTB8Y8PbAw%40mail.gmail.com.

[Royce Taft]

Jon’s description makes a lot of sense to me. I read through the hardware reference manual on Bill’s site to become familiar with all the acronyms, and then I found this document on Bitsavers for an upgrade kit that seems to reinforce the present consensus: 

So likely at a minimum, there is an 8080-based IPB (as apposed to an 8085-based IPC) in the uppermost slot in the card cage and the two cards to support the double density drive upgrade in the lowermost slots. 

I do hope that the system is configured this way, as I would prefer to have consistency in drive density and encoding.

This is a little preemptive: does anyone here have experience writing M2FM disk images using Fluxengine/Greaseweazle?

Royce

[Vale, Martyn]

Hi Royce,

 

Welcome to the group.

 

You can create M2FM floppies using my IMG2MDS Utility with nothing more than a simple serial cable it does everything else for you including formatting the floppy. See here:

 

https://www.youtube.com/watch?v=XonRevJNwek&t=930s

 

https://www.youtube.com/watch?v=uCHvWm5drHc&t=175s

 

you may be interested in my other videos as well.

 

I also have a selection of PCB’s as well some reproductions and some new ones again all detailed on my YouTube Channel.

 

You can use Greaseweazle to produce M2FM floppies, however this needs to be done from flux files from an original floppy which I can provide if you wish to go that route although this isn’t as flexible as IMG2MDS. You can create MFM single density floppies directly with Greaseweazle using the latest version directly from an IMD file and I can supply the settings file to do this if required, you do need an FDADAP adapter however to create 8” floppies:

 

http://www.dbit.com/fdadap.html

 

Bye

Martyn.

 

 

From: intel-...@googlegroups.com <intel-...@googlegroups.com> On Behalf Of Royce Taft
Sent: 02 July 2023 21:53
To: intel-...@googlegroups.com
Subject: Re: intel-devsys Purchased an MDS-120 with goodies

 

⚠ Caution: External sender

 

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[Royce Taft]

Hi Martyn,

Thank you for the links. Great work on your IMD2MDS tool! For me, this seems like the obvious solution for making boot disks once the system is fixed up.

If the Fluxengine software, with which I prefer to control my Greaseweazle, is ever updated to handle the proper encoding and format, I may lean towards that. I’ve had great success taking an original Macintosh boot disk image and using Fluxengine to create a flux image from the IMD file, then write said flux image to a disk drive via Greaseweazle in just one command. 

On the topic of typing out a machine code program as indicated in one of your linked videos: FYI I’ve had good luck copying and pasting lines of commands or data into Teraterm, sometimes needing to tweak settings for delays between sending characters or carriage returns, rather than typing them out by hand. That’s how I prefer to send S-record files to my SWTPC 6800.

Your solution is clever because the quantity of required manually-entered code is small so hand-typing doesn’t seem too tedious, then just send the rest of the program via X-modem.

I will file all this away until I am ready to attempt writing a boot disk. 

Thanks!

Royce

On Jul 2, 2023, at 14:55, Vale, Martyn <m.v...@ucl.ac.uk> wrote:



[Royce Taft]

The lot arrived in three packages, and damage was very minimal. There was cracked plastic visible in some spots in the original listing, and only a few more cracks and one chipped off piece arose during shipping. I feel confident that a little superglue will make it much better. I removed the CRT shield to verify that the neck hadn’t broken or cracked during shipping, and it looked good. 

The mystery of the cards in the system is revealed! I was able to carefully remove the cover that the seller didn’t feel comfortable trying. The board set on the bottom is indeed a double density set.

The real surprise is that the CPU card is not an 8080-based IPB like I had assumed (based on the model number ending in 20), but rather it is an 8085-based IPC.

Unfortunately, no other interface cards were in the lot. 

I have some other projects on my bench right now, so it will be some time before I get around to disassembly, cleaning, and testing. The system is VERY dirty. Not just dust, but grains of sand, spider webs, and spider nests. Almost all screw heads are rusty, of course.

Was it found stranded in the deserts of Arizona??

Don’t get me wrong; I’m very happy with this purchase and am looking forward to diving into the restoring it!

[roger arrick]

Looks great.  Just needs typical cleanup.
You don't need any IO cards, all the IO you need is on a board in the back.

Most of the problems will be connections, and a few capacitors will need replacing.

--  Roger Arrick -- Tyler, Texas, USA -- Ro...@Arrick.com --

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Sent: Thursday, July 6, 2023 8:19 PM
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Subject: Re: intel-devsys Purchased an MDS-120 with goodies

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