Beautiful systems, even if this one is in a shitty state to start with. Getting an external video card to run is non-trivial, so that VGA cable mod is probably the easiest and definitely least invasive option. Beware shorting, sparky PSUs. I have had three, one was dead to start with, the other died after about an hour of use. Fingers crossed that the third one doesn't fail (still have second one and intend to fix - some day...)

Which keyboard did you get? The Keyboard 1 or the Keyboard 2?

Neither actually. I got this:

https://www.ebay.com/itm/Vintage-Xerox-Keyboa … 872.m2749.l2649

Which should work on an M24.

vladstamate wrote:

Neither actually. I got this:

https://www.ebay.com/itm/Vintage-Xerox-Keyboa … 872.m2749.l2649

Which should work on an M24.

Interesting, doesnt look like either keyboard but certainly has the same connector. Hope that it also has the same protocol...

You seem to be a hardcore vogon... daring to touch these ticking bombs.

Back then in 1985 friends of mine sold the M24 in their shop, and I liked the display, sort of a mix of CGA and MDA on the monochrome screens.
I seriously doubt you can use a "normal" VGA monitor on that thing.
Make sure to test it using an early (!) multisync/multiscan monitor which is able to work using frequencies down to 15kHz. These are very rare by now, too.

I'd leave the on-board graphics intact, if possible. It's fine for 808x games, I think.
Here's a great video by Trixter about the M24's sister model (AT&T 6300): https://youtu.be/mUCh46_MzZU
(Source: http://www.vcfed.org/forum/showthread.php?688 … an-I-do-with-it)

retardware wrote:

I seriously doubt you can use a "normal" VGA monitor on that thing.
Make sure to test it using an early (!) multisync/multiscan monitor which is able to work using frequencies down to 15kHz.
These are very rare by now, too.

Hi, what about some cheap hybrid TV+VGA LCDs as an alternative ? They have to support 15Khz in order to display NTSC/PAL.
Both my sisters LCD TV and my NEC MultiSync (LCD 1550ME) were able to display various old tele game consoles
and most prominently, the Atari ST's hi-res monochrome mode (also 640x400, but with near VGA sync). 😀

Many LCDs have only a set of preset frequencies.
For example, the AOC LCD in my workshop failed to sync when I replaced the 14.318MHz crystal on the ET 4000 card for my 486 with an 18MHz one, to reduce flicker on the CRT monitor. The CRT syncs just fine.
I'll test on a DELL 2007FP LCD soon. Just curious whether this LCD, which is said to be good for retro, is able to sync with odd (i.e. non standard) frequencies.

Edit:
Another example is the Eizo 4051, which was popular from the mid-1980s.
It was just a MDA-alike monitor, but running at a higher frequency (together with a matching Eizo MDA video card). This allowed for 70Hz refresh.
Around 1990 I got two of these monitors ultra-cheap (100 Deutsche Mark) because the video cards were missing, and connected them to HGCs that I ran with 22MHz instead of 14, resulting in 80Hz screen refresh after some monitor readjustment - flicker-free even in positive. Very convenient as second monitor for debugging!
The Olivetti display was something into that direction: better refresh than CGA, less flicker - just ergonomic for that time.

From what I've read, the Olivetti M24's monitor uses a horizontal frequency of 25.9 KHz (not 15 KHz).
Most of the older LCD's can sync to that frequency but, not that many VGA CRT monitors (unless you have an NEC multisync or similar monitor).

You cannot remove the Olivetti M24's graphics card, since it also doubles as an interface between the motherboard and top section which has all the slots.
You can either disable the graphics card and then use an 8-bit compatible VGA card (jumpers must also be set on the motherboard and graphics card, depending on the revision) or, use the adapter cable and connect to a monitor that can sync to 25.9 KHz.

jesolo wrote:

horizontal frequency of 25.9 KHz (not 15 KHz). ..... .... You can either disable the graphics card and then use an 8-bit compati […]
Show full quote

horizontal frequency of 25.9 KHz (not 15 KHz).
.....
....
You can either disable the graphics card and then use an 8-bit compatible VGA card (jumpers must also be set on the motherboard and graphics card, depending on the revision) or, use the adapter cable and connect to a monitor that can sync to 25.9 KHz.

Correct.

If you have a compatible monitor, you can build an adapter.
But the easiest way is to put a new video card in one of the many expansion slots (if your m24 has the 'big' expansion card)
Like i did with my Paradise Vga, which is a 16 bit card, but worked fine in a 8 bit slot! (at least in b/w)

You have to set jumpers group 1 to EGA (but you need a board with the latest bios which is 1.43)

Btw my poor m24, salvaged from dumpster, worked fine, until i had the great idea to put one of those isa diagnostic cards made in china. I swear i did put it correctly, but it shorted. I think i've fried some logic gates and now i'm trying to find the broken chip, out of the dozens on the main board... mission impossible. Don't try unknown shit in your favourite pc, the lesson i've learned.

mongaccio wrote:

If you have a compatible monitor, you can build an adapter.
But the easiest way is to put a new video card in one of the many expansion slots (if your m24 has the 'big' expansion card)
Like i did with my Paradise Vga, which is a 16 bit card, but worked fine in a 8 bit slot! (at least in b/w)

I will try both. I have the parts to build an adapter, so I will do that first, as it is least invasive to the machine itself.

mongaccio wrote:

You have to set jumpers group 1 to EGA (but you need a board with the latest bios which is 1.43)

I assume there is no way to know what BIOS I have without powering it on and seeing something on a screen right?

mongaccio wrote:

Btw my poor m24, salvaged from dumpster, worked fine, until i had the great idea to put one of those isa diagnostic cards made in china. I swear i did put it correctly, but it shorted. I think i've fried some logic gates and now i'm trying to find the broken chip, out of the dozens on the main board... mission impossible. Don't try unknown shit in your favourite pc, the lesson i've learned.

Good advice. I have one of those, and now I know NOT to put it in 😀 I have it in a XT 286 machine.

vladstamate wrote:

I assume there is no way to know what BIOS I have without powering it on and seeing something on a screen right?

Actually it should be easier.

You should have the bios revision number on the lower and upper eprom chip labels. Like mine

vladstamate wrote:

I have one of those, and now I know NOT to put it in 😀 I have it in a XT 286 machine.

Oh well, if it works on another pc, it should work on the Olivetti. *SHOULD* 😠 My mistake was trying it on the M24 first hand. IMHO i recommend not to put modern isa cards anyways.

I have an AT&T PC 6300, which is basically just a rebranded version of the Olivetti M24. Just a small warning if you decide to go probing the video connector to make your own cable, some of the video connector pins are live at full 120/240VAC. The proprietary monitor designed to go with the M24/PC 6300 uses a single cable to carry both video and power, and the computer itself provides the power.

Also, just FYI this system is not 100% IBM compatible. Rather, it's one of those "it runs Lotus 123, that's good enough" levels of compatibility. 😜

Hi ,just found another interesting thread at the Vintage Computer Federation forum.. Hope you don't mind for me mentioning that. 😅
It's called "Another discussion of CGA/EGA on (relatively) modern monitors" and the AT&T 6300 is also mentioned there.
Apparently, some of the newer LCDs (widescreen, Asus etc) can sync to uncommon rates..

Hi,

Did you need to disable the video card when you put the paradise VGA card? Did you disable it with jumpers on the video card or you had to apply a procedure where you had to desolder a component? My card does not have the W1, W2, W3 jumpers.

mongaccio wrote:

Correct. […]
Show full quote

jesolo wrote:

horizontal frequency of 25.9 KHz (not 15 KHz). ..... .... You can either disable the graphics card and then use an 8-bit compati […]
Show full quote

horizontal frequency of 25.9 KHz (not 15 KHz).
.....
....
You can either disable the graphics card and then use an 8-bit compatible VGA card (jumpers must also be set on the motherboard and graphics card, depending on the revision) or, use the adapter cable and connect to a monitor that can sync to 25.9 KHz.

Correct.

If you have a compatible monitor, you can build an adapter.
But the easiest way is to put a new video card in one of the many expansion slots (if your m24 has the 'big' expansion card)
Like i did with my Paradise Vga, which is a 16 bit card, but worked fine in a 8 bit slot! (at least in b/w)

IMG_20190329_142045.jpg

You have to set jumpers group 1 to EGA (but you need a board with the latest bios which is 1.43)

IMG_20190329_141955.jpg

Btw my poor m24, salvaged from dumpster, worked fine, until i had the great idea to put one of those isa diagnostic cards made in china. I swear i did put it correctly, but it shorted. I think i've fried some logic gates and now i'm trying to find the broken chip, out of the dozens on the main board... mission impossible. Don't try unknown shit in your favourite pc, the lesson i've learned.

tonata wrote:

Hi,

Did you need to disable the video card when you put the paradise VGA card? Did you disable it with jumpers on the video card or you had to apply a procedure where you had to desolder a component? My card does not have the W1, W2, W3 jumpers.

It depends which graphics card you have. Based on what I've read, on earlier revisions of said graphics card, you need to remove some chip and then replace it with a "bridge" chip to bypass the M24's graphics card.
The last revision of the graphics card had jumpers on the card that allowed you to disable the card.
I've tried it once with my M24 and I couldn't get it to boot up with an external card since, at that point, I didn't know I had an earlier revision of the graphics card.
I'm actually more interested in making my M24 work with the on-board card, as opposed to using an external 8-bit (or 16-bit that will work in an 8-bit slot) VGA card.

I have finally repaired my broken M24! It was a broken logic gate on the ISA slot board...

I can confirm , if i place my Paradise Vga (ISA 16bit) in a slot, and change the M24 switch 5,6 of group 1 to 'ON', i have a vga video output (albeit in Black and White)
I am lucky to have a later revision of the board.
And i'm really lucky to have one ISA card that somehow works in the 8 bit slot. (it's an Olivetti branded card btw)

I should try with other cards, now.
Unless i find a cheap 8 bit ISA video card...
I've also tried with a homemade adapter to the original video card exit,but i don't have a compatible monitor: some of my monitors display 'out of range' error

All in all it's a good start, i'll probably have some fun trying various things .Like trying to get that card working in color mode

I might be able to help you with a crucial piece of the puzzle here! 🙂

Years ago, I asked people on the the Vintage Computer Forum whether they could help me obtain the so-called "Bus Correction Kit", an obscure aftermarket product for the Olivetti M24, which someone back in the day developed to fix incompatibilities in the M24 bus that would cause problems with EGA and VGA cards in that system, at least in some software. Forum member Chuck(G) had one of those kits, made pictures of it and made a dump of the PAL (or GAL?) chip. Another forum user named keepiru used those binary dumps and the pictures to actually recreate one. He offered to send it to me, but I didn't check the forum daily, so by the time I read his offer after some time had passed, I couldn't get ahold of him anymore. 🙁

However, the design files of the reverse-engineered recreation of the Bus Correction Kit can still be downloaded from that forum thread and could be used to make some new batches of this device.

http://www.vcfed.org/forum/showthread.p ... vetti-M24)

If anybody with the necessary skills is prepared to take up the challenge of having more of these bus correction kits produced, I would certainly get in line to order one! Getting EGA graphics to work on my Dad's Olivetti M24 has been this life-long dream and kind of a sacred Quest for the Holy Grail for me, ever since I was a kid. 😊

Speaking of the M24 and the Vintage Computer Forum, I just found this other topic where someone shared the design of the "M24-IDE", a variant of the XTIDE card that takes advantage of the proprietary 16-bot bus of the Olivetti M24. That is incredibly cool, since hardly any cards were made that could take advantage of it. If someone plans on a production run of those, I would be on board with that as well, of course. 😀

http://www.vcfed.org/forum/showthread.php?669 … 4-AT-amp-T-6300

So, those Bus correction kits are needed for older revision boards, right?
The newer ones like mine has those jumpers and that PROM 'Pqb1' already on board that does the job, if i understood correctly.

I'm starting to read that thread on the other forum, the m24 IDE 16 bit project is really cool.
I hope that Valerio completes his project (he mostly did it but he has some issues, sometimes it doesn't work properly ) . He seems really a pro, he has some testing equipment to check the IDE bus, so i 'm pretty confident he will find all the issues!

mongaccio wrote on 2020-05-26, 15:59:

So, those Bus correction kits are needed for older revision boards, right?
The newer ones like mine has those jumpers and that PROM 'Pqb1' already on board that does the job, if i understood correctly.

No, these are different issues. What you are referring to is the ability to disable the onboard graphics controller to allow a separate graphics card to be installed at all.

The bus correction kit however corrects an incompatibility w.r.t. to the "byte order" in which words (16-bit values) are sent to 8-bit ISA cards. It happens to be the exact reverse of what IBM picked when they introduced the PC/AT with another 16-bits bus after the M24 was designed. The bus correction kit applies some kind of hardware hack that swaps this order to fix compatibility with some graphics software. Particularly, graphics software that programs the I/O registers of EGA and VGA cards directly using 16-bit writes tends to be affected. Software that use the VGA BIOS and/or 8-bit writes run fine. At least that's how I understand it.

Also, according to one other person who replied in that VCF thread, this bus correction kit might also have a jumper that changes the operating frequency of the expansion bus from 4MHz to 8MHz, the frequency at which the CPU and RAM are already running. If that is actually true, that should result in a significant additional performance boost, in addition to solving any incompatibilities with some software using EGA or VGA cards installed in this system.

I'm starting to read that thread on the other forum, the m24 IDE 16 bit project is really cool.
I hope that Valerio completes his project (he mostly did it but he has some issues, sometimes it doesn't work properly ) . He seems really a pro, he has some testing equipment to check the IDE bus, so i 'm pretty confident he will find all the issues!

Yeah, I too am glad that highly skilled hardware wizards with a pashion for retro computing exist. 🙂

Once he gets that IDE card stable, perhaps there are additional interesting things that could be made for this bespoke 16-bit PC architecture, such as for instance a 16-bit EMS expansion card. Those already exist for the M24 (from AST I believe), but they are very rare.

Thanks for the explanation, now i understood better what's the issue.

digger wrote on 2020-05-26, 17:27:

Once he gets that IDE card stable, perhaps there are additional interesting things that could be made for this bespoke 16-bit PC architecture, such as for instance a 16-bit EMS expansion card. Those already exist for the M24 (from AST I believe), but they are very rare.

I sure hope so.
Many years ago i had this beautiful m24, i sold it to an ex Olivetti employee that set up an Olivetti museum here near home.
Had one memory expansion board that took nearly all the case length, filled with memory Ics, and a color monitor, also a 3.5 inch floppy.
It was really a great machine,but the card inside was indeed so rare(at least the 16 bit ones) i've never seen one around, not even online.
I think that guy was mostly interested to the original color monitor which is quite rare too.
Sometimes i do regret my sale, i mean, it went to a museum, at the time i wasn't that interested in old pcs...
I did find my current one at the dumpster(back when we could freely rummage through the hi-tech bins without problems),but it was barebone, no expansion cards.
Found a compatible keyboard a couple of years later, at a flea market, and i still consider it a lucky find.