MPF-I/88

C'est la catégorie reine de l'ordinophile, 8 bits et pas un de plus!
Single board ou bus S-100 acceptés.

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Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

J m'appelle Ruud et je vie en les Pays Bas. Ma Francais nést pas bien, je m'excuse et je veux continuer en Anglais.

First a bit of history. My first computer was a Commodore 64. After an internship with Elektor, the electronic magazine, I received a Junior. During another internship I worked with the MPF-1B. My first job was in a shop of a classmate and we assembled PCs. This was the start of my love for the Intel 8088/NEC V20. In those days I learned of the MPF-I/88 but I couldn't afford it. And having free access to all kind of PCs didn't help either. Why did I want one? Because of its simplicity, just like the MPF1B.

I have created some boards, for example http://baltissen.org/images/6502miniTTL.JPG (for more info: http://baltissen.org/newhtm/ttlcpus.htm), and due to remark someone made I said to myself: why not building one yourself?

In the past I had collected some info but due to an error of a hard disk that even affected the back-ups, I lost most. So I started googling. In the very beginning of October 2020 I found this thread but there were only two messages then. I gave it another try last week and first hit Leo Bodnar's site. This on its turn lead me to this thread again seeing that there was all the information I needed.
What are my plans/ideas:
- One thing that survived the crash was the schematic I created in Eagle. But I noticed an error and w/o the original schematic I couldn't do anything. I found that one on Leo's site. Having a corrected schematic, I can create a PCB now. But then one with at least 64 KB of EEPROM and 512 KB of SRAM. This and some other little changes are discussable of course.
- The ROM(s) I found on this thread. Then I found out that I had a ROM as well. But it was different from the one I found, roughly 50 bytes. Meant for a MPF with a different keyboard? (I have seen a picture of a MPF with German keyboard).
- I found various manuals, one with the source listing. This one enabled me to disassemble the ROM I found here in no-time using my own disassembler. Adding the various comment and replacing various number by labels is the next step. Just one remark: my disassembler produces sources for NASM and NASM outputs a different binary code for some instructions compared to MASM. So although a binary file compare shows differences, the NASM code does exactly the same as the MASM. FYI: this has been proven by some IBM freaks who didn't believe it in the first place. But I'm thinking about letting my disassembler to output MASM code as well.
I want to stick to the original ROMs anyway but the source listing enables one to make some changes or improvements if needed. It is easier to understand than the paper one and one can add extra comment to clarify things, if needed.

Cordialement je vous salue, Ruud Baltissen

http://baltissen.org
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

I have finished checking the schematic that I had in Eagle against the the one found in the Reference manual / JPGs provided by Leo.. I found some differences, some severe:
- minor ones: a missing resistor and capacitor, different values for some parts.
- an error in the schematic: the paper one says "ear (audio input)" and "micr (audio output)", mine said only "ear" and "micr" only. But they draw my attention because I couldn't match the circuit with their function. IMHO it should be clear that it should be "ear (audio output)" and "micr (audio input)".
- The pictures show clearly that there are connectors between the main board and the keyboard, between the main board and the little PCB in the case with the LEDs and the reset button, and (more or less) between the main board and the LCD. In my case the schematic provided two connectors for the LCD: a 2*7 and a 1*14 pin one.
- the most severe one: have a look at page B-3 of the manual / JPGs.There is a signal going to transistor Q2 / the audio output. According the schematic its source is both pin 5 and 6 of IC21 (which is an error because both pins are outputs). My schematic only uses pin 5. The source code will provide eventually what pin is used but for the moment I would be very pleased if someone gave me a visual proof.

Next step is to make a PCB of the schematic. But why not improving it a bit if we can?
- Replace the three 27128s with one 27512 or EEPROM/FlashRAM. The advantage of an EEPROM: much faster to erase and program. 1st idea: use a 29F010, 128 KB, but for the 0F000 segment (= 64 KB) only. 2nd idea: use a jumper to select which 64 KB part to use. 3rd idea: use the free pin 6 of IC21 to select the 64 KB part. A jumper can en/disable this function.
- Replace the three RAMs with one 512 KB one. I tend to add a second one as well but that could be overdone. It would also mean I would need to provide a circuit to exclude the last segment.
- Replace IC10 and some gates of IC4 with an original 8284. Officially the 8088 needs a 33/66% duty cycle clock. It can handle 50/50 ones but..... Using an 8284 has the following advantages: 1) correct duty cycle clock, 2) less parts needed 3) we can add a 24 MHz oscillator so it can run at 8 MHz as well.

Give me your opinion or ideas, please!

Cordialemant, je vous salue, Ruud Baltissen

www.baltissen.org
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
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Falkor
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Re: MPF-I/88

Message par Falkor »

Hi, and welcome here !

It looks like that you have made a very nice job on this, could you please share some pictures ?

In the future, if there is a way to build one from scratch, I'm definitely in :)
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

I forgot to mention another difference: in my case the F2 and Capslock were connect to the same row as the Ctrl key. Could this have been a mistake from my side? I did not re-engineer this schematic so it has to be copied from an electronic one. I am humanAFAIK, so I can make mistakes. But placing two keys so out of line ???
FYI: these Eagle schematics were produced in 2005.

Regarding the schematics, I'll place on my site were you can download them.

Cordialement, je vous salue, Ruud Baltissen

www.baltissen.org
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

The promised schematics as PNG:
http://www.baltissen.org/images/KB.png
http://www.baltissen.org/images/MPF88.png

The Eagle files and used libraries are free (as all of the stuff on my site), email me so you will have the latest versions. If you are a KICAD fan, there are tools to convert these files.

Have fun!
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

I forgot to ask: could anybody give me the dimensions of the main board. I also need to now where the various connectors and screw holes are situated. I prefer to make a board that can replace the original.

Merci beaucoup!
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

The improved version, MPF-I88B: http://www.baltissen.org/images/MPF88B.png

- I replaced IC14 (74LS107) with the 8284. This ensures a correct clock when going faster.
- The 8284 enables us to select between 4.77 and 8 MHz. JP9 takes care of that.
- 64 KB of FlashRAM. JP4 enable us to select which 64 KB part of the total of 128 KB is used.
- 512 KB of SRAM
- JP4 and JP9 enable us also to use output 6 of IC21 to choose what 64 KB part or what speed is selected. You are free to use it only for the speed selection, only for the ROM selection and even both!

At the moment one can only select one interrupt from the expansion bus as input for the 8088's interrupt. My change freed three OR gates and they can be used to cover all four inputs, no jumper needed anymore. Software should find out what the actual source of the interrupt was.
At the moment the IRQs 2, 3, 4 and 7 are monitored. Monitoring IRQ6 is used by drive systems so I would rather prefer 6 instead of 2. IRQ5 is used by some sound systems. 3 and 4 are both used by RS232, one to many? Using jumpers again does enlarge the selection. Your opinion, please.

I'm sure I gained room with the new configuration. Another idea is to add connectors for the AT power supply. One can choose between the original power supply and the AT one.

Ideas from your side are welcome!

Edit: I just found out that the INTA signal is not connected to pin B6, as I thought, but pin B5, used by IBM for -5V. I'll change that in both version and in my B version I'll use a jumper to let the used choose between -5V and INTA towards the external edge connector.
Dernière modification par Ruud le 11 janv. 2021 09:27, modifié 1 fois.
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
leobodnar
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Re: MPF-I/88

Message par leobodnar »

I have added the scan of the bottom of the PCB
It has a resolution of 10 pixels per mm so you can easily get your coordinates by measuring it in any graphics editor.
The distance between two furthest screws that hold the PCB down seems to be 190mm.
Leo
Ruud
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Re: MPF-I/88

Message par Ruud »

Hello Leo,

Very impressing, thank you very much!
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

While creating the board I made a bit shocking discovery which lead to the question: what is the use of the internal connector? The distance from pin A1 to the edge of the board is 0.85 inch = 21.6 mm. I had some cards laying around and measured more then 23 mm. The distance between the metal bracket and pin A1 was always 1 inch. In other words: a normal card simply won't fit!

The only thing that could fit is the risercard of one of those old flat desktops like the Commodore 386-25. And even then you still have to saw a piece of so it fits inside the case. So again, what is it good for?
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
Ruud
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Re: MPF-I/88

Message par Ruud »

Bonjour,

As promised to create a new board for the MPF-I/88. It has (in my eyes) many improvements but its IMHO still 100% compatible.

Image

A full size picture can be seen at http://baltissen.org/images/MPF88B-brd.png

But first I want to thank mr. Leo Bodnar who provided me with a scan of the bottom of the original board. Very smart: the picture was 10 pixels/mm so figuring out where the various holes and connectors should be was a piece of cake.

Changes in the new design:
- New clock circuit using the Intel 8284 as used by the IBM PC.
Advantages:
- correct 33/66 clock phase, needed for higher speeds
- switchable between 4.77 or 8 (maybe 10) MHz by jumper and software
- 512 KB of RAM.
- 128 KB FlashRAM, only 64 KB accessible, switchable by jumper and software.
- I used the not used output D5 of U21 to switch the speed and/or ROM.
- I added a PC AT power connector.
- Not having an original case I added two LEDs.
- By using the 8284 I freed three OR gates. These enable me to connect four interrupts to the interrupt input of the CPU. I used the original jumper block to add the other two interrupt signals that were not selectable so far. The block enables you to chose between interrupt 2 or 6 and 3 or 5.

- I moved the original power converter to the right side of the board to shorten the primary line and that saved some space.
- I replaced the original 62-pin connector with a 64-pin DIN A-C one. You can still place a 62-pin ISA slot if you want to, so so far actually nothing changed. I prefer the DIN connector because it is a more stable platform for a riser board than an ISA slot.
- I moved the internal connector to a place that made it easier to draw lines. I already figured out that it couldn't be used to insert original PC cards because the side of the case is in the way. But that is no problem for a riser card.
- I rewired the various connectors: other than the original output/input pins drive/read the pins of the keyboard and printer connector. Of course I also swapped the data pins accordingly. Seen from the point of view of the software nothing should have changed.

- With the exception of the internal connector, all other connectors are at the same place as on the original boards.
- I didn't place any holes on the board (yet), I just outlined them on the board.
- After drilling the holes yourself, I'm sure that this board can replace the original one.

I won't produce the boards yet, I also need a keyboard and have to figure out yet how to get/build one. In the mean time I'll check the design again and you are welcome to give your input/comment.

The Eagle files are free but you have to PM me to get them. You can find my email address on my site. A picture of the schematic: http://baltissen.org/images/MPF88B.png

Have fun!
Dernière modification par Ruud le 17 janv. 2021 11:44, modifié 1 fois.
Cordialement, je vous salue / met vriendelijke groet, Ruud Baltissen

www.baltissen.org/newhtm/index4.htm
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Falkor
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Re: MPF-I/88

Message par Falkor »

Amazing work, congrats !! :)
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jeffounet
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Re: MPF-I/88

Message par jeffounet »

FANTASTIQUE!

Very nice job!!

Jean-François
Il n'y a que 11 sortes de gens, ceux qui comprennent ceux qui ne comprennent pas et ceux qui me font répéter!
Jean-François
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jeffounet
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Re: MPF-I/88

Message par jeffounet »

Bonjour à tous,

Le MPF-I88 le retour.
Bon j'ai reçu ce mois-ci diverses choses que j'avais commandés pour faire quelques essais. Ayant reçu la dernière carte ce matin (bien celle qu'il me fallait en premier est arrivée en dernier!!!).
Donc voici les premier tests. et pour la mise en bouche un MPF-I88 avec 640kO de RAM au lieu des 24kO maxi annoncés!
On vois sur la photo le MPF équipé de la carte 640kO (1MO en réalité mais les derniers 384kO sont désactivés pour éviter certains conflits) ainsi que la carte CGA.
.
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Devant l'écran, sur la table les 3 RAM de 8kO chacune qui ont été retirée du MPF.
Une petite photo de près, prise lors du premier test sans carte vidéo.
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les photos de la carte RAM:
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Voilà pour la première partie, j'ai donc un MPF-I/88 avec 640kO de RAM fonctionnelle, en effet au démarrage le MPF teste la RAM et le temps de test des 640kO est considérablement plus long que pour les 24kO ce qui tend à prouver que la mémoire fonctionne! maintenant il va falloir faire les test logiciel!

Voilà pour ce premier post.
La suite arrive.

Bonne journée

Jean-François
Il n'y a que 11 sortes de gens, ceux qui comprennent ceux qui ne comprennent pas et ceux qui me font répéter!
Jean-François
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jeffounet
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Re: MPF-I/88

Message par jeffounet »

La suite du matériel reçu:

une carte contrôleur de disque dur pour XT en ISA 8 bits:
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20210128_142147.jpg
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20210128_142157.jpg
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Ainsi qu'une carte contrôleur FLOPPY:
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20210128_142223.jpg
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Et une carte double ROM:
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20210128_142239.jpg
20210128_142239.jpg (120.59 Kio) Consulté 1054 fois
Etant limité à 5 photos par post, la suite ci-après.

Jean-François
Il n'y a que 11 sortes de gens, ceux qui comprennent ceux qui ne comprennent pas et ceux qui me font répéter!
Jean-François
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