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Multitech MPF-PC 552 misbehaving

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First post, by waterbeesje

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I've got this Multitech MPF-PC 552 for about 4 years now, but never got it to work as expected.
It's an IBM PC clone. It came with original Multitech keyboard and Multitech monochrome CGA screen (composite).
I think it's something special, because I have only seen exactly one more.

The attachment Multitech MPF-PC.jpg is no longer available

Specs:
D8088 processor,
256kB RAM,
FDD controller onboard
5.25 "FDD (tested in different 8088 system, working),
CGA graphics card,
DTC 5150BX 2 MFM controller
MFM hard disk (Shugart 712, 10MB).
Original keyboard
Monochrome monitor (Composite connection for image, with such a lovely high pitch).
This computer came in as not working, plug-in cards and FDD cable were loose and the MFM cables (control and data) were missing.

The attachment Multitech.jpg is no longer available

(mfm controller left out here)

I have put everything together and the computer:
- gives a picture, ram is tested (motherboard, CGA card and monitor therefore work)
- the FDD is being initialized (and tested on my Philips XT computer: works fine)
- the HDD is marked as present by the controller (and tested on my Philips XT computer: works fine)

---

Question and story one: the boot floppy.

With the HDD disconnected / controller removed and a floppy disk in the diskdrive (both PC-DOS 3.3 and PC-DOS 5.02 tried) it reads the floppy, and says 'DIOS.COM NOT FOUND' It seem to need this to boot, because the system hangs.
At this pont hitting a random key makes the computer retry to read the floppy disk and returns the same error.
The boot floppys work perfectly with my Philips.

I tried:
1. With my Philips XT I made a fresh boot floppy with PC-DOS 3.30 (using the Multitech FDD to eliminate drive incompatibility). Then I put some standard external commands on the floppy (debug, format etc) and tried to boot the Multitech. No success.

2. Next I copied the IBMBIO.COM as DIOS.COM (just some trial and error, assuming this wouldn't work but who knows) The Multitech turns on, and without the HDD I get the message "DISK BIOS LOADING", followed by the message that it is the wrong version (duh ...) and I have to press [ctrl] [alt] [del] to reboot and get the same error ofc. Conclusion: the floppy drive and floppy both work. DIOS.COM not yet.

3. dug up a bunch of DOS boot disk images on WinWorldPC and checked them for a DIOS file: zero success.

4. dug even deeper on Google, Bing, Yahoo and DuckDuckGo. DIOS.COM seems untraceable: (the only clues are a thread on VCFED.COM and vintagesbc.it where someone also ran into this.

5. Downloaded a CP/M 86 image and it will acyually boot until it hits i/o port errors when trying to initialize them... and hangs.

Now I know that there are people here who also have a lot of old/odd/irregular computers. So my question: Does anyone have this DIOS.COM for the Multitech MPF-PC? I only need this file, however a DOS disk image would be convenient.

Could it be that I need a revised BIOS for this computer? (the chip is a M5L2764k labeled "Multitech BROM 1.1" so perfectly replacable)

---

Question and story two: the keyboard.

The hard disk came with this computer and I hooked it up to see if it did something: it only was reported presend by the controller, but did not boot.
As part of my search for a solution, I hooked drive and controller up to my Philips XT and again: hard disk presend, no boot. From boot floppy the drive was not recognized and not readable.
Any AT computer or higher wouldn't help me at all, the ROM was not initialised.
Back to the Philps: I hooked up fdd and hdd (with the controller) from my Multitech and booted from PC Dos 5.02 and after low level + high level format the hard disk did actually boot and seems to have very little bad sectors.

Put FDD/HDD/controller back to the Multitech and it boots from HDD immediately!
And the the keyboard does no longer respond.

Put the boot floppy in (see problem above) and rebooted: any key stroke retries to load DIOS and fails again. Keyboard must be working...

Do I need to preparate some settings / driver to be able to use the keyboard?

side note 1: I really want PC-DOS 5.02 because it's able to use Interlnk / Intersvr and the Scandisk from the Win98 boot disk)
side note 2: Due to this keyboard error I have put PARK.COM into Autoexec.bat, which I can exit by pressing a key. Safe to turn off the computer, and the best test to see if the keyboard does *anything at all* after booting
side note 3: the Multitech keyboard is a standard XT type and works flawless on my Philips. The Philips XT keyboard works fine but also refuses when connected to my Multitech.
Side note 4: I can toggle the caps lock: the LED on the keyboard switches on and off.

---

Found a quite similar board in this thread:
Need help identifying 8088 motherboard

For a bit more information about this computer (in Italian, use your favourite translatorwhen convenient):
http://www.vintagesbc.it/?page_id=151

For a little discussion on VCFED:
http://www.vcfed.org/forum/showthread.php?261 … -8088-need-help
(last post is mine 😀 )

Stuck at 10MHz...

Reply 1 of 11, by weedeewee

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I'm intrigued. Could you post detailed pictures of the boards, harddrive controller etc... ?
The failing to load DIOS.COM makes me think it's trying to load a ROM image from the floppy, possibly to access the hard drive .?
The keyboard problem reminds me of the Olivetti M24, which didn't like the keyb executable that was present with the normal DOS versions. You had to use the Olivetti dos version to get the keyboard to function with the correct layout. If you didn't have that... boot ok, keyboard driver load -> no keyboard.

Right to repair is fundamental. You own it, you're allowed to fix it.
How To Ask Questions The Smart Way
Do not ask Why !
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Reply 2 of 11, by waterbeesje

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I'm back! We just had our annual week of snow, so all week long I've been towing a little sled with my son thru the streets.

I did make some nice pictures of the computer and it's internals, and a little video with the lovely sound of the hard disk. Some photos were about 20MB and I don't think the Vogins compression will do them any good... So I zipped then.
The zip file became just over 300MB so be aware of that when downloading.
https://www.dropbox.com/s/4h1f37h5mzboljf/Camera.zip?dl=0

@ ultimate hardware 19 team: feel free to use them if you like.

The keyb things is quite interesting, I thought I'd need it actually to get things right... But this could be something as well. The layout seems pretty standard US to me, and the keyboard looks like it's original... so maybe it doesn't need a driver at all.
I'm going to check that one out later on.

Stuck at 10MHz...

Reply 3 of 11, by Horun

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Nice old XT !

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 4 of 11, by weedeewee

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waterbeesje wrote on 2021-02-16, 00:02:

I'm back! We just had our annual week of snow, so all week long I've been towing a little sled with my son thru the streets.

Yes, we've had a few days of snow, and a week of cold as well. 😀

I did make some nice pictures of the computer and it's internals, and a little video with the lovely sound of the hard disk. Some photos were about 20MB and I don't think the Vogins compression will do them any good... So I zipped then.
The zip file became just over 300MB so be aware of that when downloading.
https://www.dropbox.com/s/4h1f37h5mzboljf/Camera.zip?dl=0

Sweet ! Thanks !

Right to repair is fundamental. You own it, you're allowed to fix it.
How To Ask Questions The Smart Way
Do not ask Why !
https://www.vogonswiki.com/index.php/Serial_port

Reply 5 of 11, by pentiumspeed

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Once you get this XT working, you'll want to upgrade to 640K which replaces 16 chips or 18 chips with 256K x 1 dram chips. 256K does not do much with most late era XT software.

Did you check the switches are correct for this configuration and if not working right, you might have one of IC or socket is bad.

The motherboard's keyboard connector contacts has habit of loosening up with plugging and check your keyboard for quality of solder joints.

Cheers,

Great Northern aka Canada.

Reply 6 of 11, by waterbeesje

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Thnx all! 😁

The switches are definitely not in their right position, that's something I still have to figure out. The system gives me some I/o errors on boot. Thinking of it: that may also create a conflict with the keyboard perhaps...

256kB to 640kB is something I'd like to do if I get it up and running. I'm not sure the machine supports 41256 chips, but I do have an ISA add-on card to provide 4 extra banks, already populated with 256kB (36 chips, 4164). This add-on also supports 41256 chips so it should be ok once I get some more 41256 chips. (Or 18pcs 1M X1 chips to upgrade my 286, which make 18pcs 256kx1 available instantly)

Stuck at 10MHz...

Reply 7 of 11, by waterbeesje

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Sorry for the necropost... But I've got this thing working!
After trying several boot disks with several dots and CP/m-86 versions I finally got one specific image to work.
The Dr Concurrent PC Dos 3.2 disk set.

The attachment IMG_20240927_224627.jpg is no longer available

It appears the startup disk is formated in 320kB rather than 360kB, called CP-M media by the system. The system is looking for a CP/M compatible boot sector and loads anything that followed...

The attachment IMG_20240927_224243.jpg is no longer available

But the more common so called DOS media are just fine too for reading and loading stuff.

The attachment IMG-20240927-WA0020.jpeg is no longer available

(Sorry for the bad pics, was too excited to take my time)

Stuck at 10MHz...

Reply 8 of 11, by waterbeesje

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Again some time put into this puzzle. And a puzzle it is...

I've figured out the system only boots the floppy of the a CP/M bootsector. I've tried about 20 different versions of DOS and CP/M that are IBM compatible. No single MS or IBM does will boot. CP/M boots fine and Concurrent DOS up to 4.1 boots as well.
And as a little bonus, the Gotek with flashfloppy is also working fine.

The hard drive becomes inaccessible when C Dos 4.1 is loaded, even when I try to install It, it says there is a hard disk but gives me rubbish errors.

I tried:
- put MS Dos 3.30 onto a floppy disk that previously contained a working C Dos 3.2 boot sector. Fails. Boots fine on my K6 system.
- create a bootable PC DOS 320kB disk. Fails. Boots fine on my K6 system.
So I guess I can forget about MS/PC Dos...

The MFM disk works fine. I have the DOS install tuning on another PC and it still won't accept my keyboard.
I tried a XT-IDE to CF device but the system won't recognise it...
I've got several ram upgrade cards, but none seem te work.

So far the Multitech adventure... Will be continued sooner or later.

Stuck at 10MHz...

Reply 9 of 11, by waterbeesje

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Again a little progress here. I've managed to install a nice ram card to upgrade to the full blown 640kB. Iets the Persyst PC/SM card, which is recently added to Theretroweb.
https://theretroweb.com/expansioncards/s/persyst-pc-sm

An attempt to add a XT-IDE device stil fails. Ice voor several of them laying around and they dont seem te work. Even with the hard drive and its controller removed.

Maybe the bios dislikes the idea of the modern XT-IDE so recently I've been looking at the GlaBios and hope this allows me to replace the BROM labeled chip.
https://glabios.org/

I've got several EPROMs 27c64 and EEPROMs 28c64, some ultra cheap UV eraser and two eprom burners so somehow I should be able to burn it. Now I just have to drive into the rabbit hole of these burners. Luckily they're documented on the web.

Stuck at 10MHz...

Reply 10 of 11, by 640KB

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waterbeesje wrote on 2025-12-25, 00:00:
An attempt to add a XT-IDE device stil fails. Ice voor several of them laying around and they dont seem te work. Even with the h […]
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An attempt to add a XT-IDE device stil fails. Ice voor several of them laying around and they dont seem te work. Even with the hard drive and its controller removed.

Maybe the bios dislikes the idea of the modern XT-IDE so recently I've been looking at the GlaBios and hope this allows me to replace the BROM labeled chip.
https://glabios.org/

I've got several EPROMs 27c64 and EEPROMs 28c64, some ultra cheap UV eraser and two eprom burners so somehow I should be able to burn it. Now I just have to drive into the rabbit hole of these burners. Luckily they're documented on the web.

Hi there. That's a cool and rare old PC! Am very curious to hear how this goes with GLaBIOS (just use the XT 5160/8088 version), and if something isn't working right we can certainly troubleshoot and figure out if there's some kind of non-standard hardware involved.

Have you ever discovered any technical docs for it?

640KB

Reply 11 of 11, by waterbeesje

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Hi, Thanks!
It is certainly a weird thing regarding the bios. I have fate in the 8086 5160 GLaBIOS version, since al major chips match the IBM 5150/60.

I don't have any documentation at all, only the leads on vintagesbc.it. And I'm not even sure the DIP switches are configured right... With DrDos 3/4 I'm not able to load Checkit or similar programs to read out current settings. But that shouldn't limit the BIOS in first place.

With these holidays I've had only little time for hobby, family wants some attention too 😁

Stuck at 10MHz...

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