VOGONS


First post, by Deksor

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Hi, so I just got this Intertan DT-88 computer to play with.

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The computer turns on, but its hard drive, a Seagate ST325X doesn't spin up anymore (and it's not the platter that are stuck, because I can move the spindle found under the hard drive perfectly fine).
hm9vDuXl.jpg
It seems like it's a board's failure rather than a mechanical one, but I don't know what could have failed there.
Here's the board itself:
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There were bridges with "0" labeled on them. But they failed as the resistance between their two sides was inifinity ... So I took them off and bridged them back with just big blobs of tin. That should do the trick for now.
But the drive still doesn't spin.
I measured the voltages on the platters' motor and the highest voltages I saw were 0.2V ... Maybe the board just have a power failure ? I've tested the hdd with 4 PSUs so it's not just because I hooked it to a potentially bad PSU.
I thought that maybe caps would be the next target for components that may have failed ...
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I also measured the voltages on these two transistors and I noticed something odd :
Ocd4IZtl.png

Now I don't know what these transistors are supposed to do nor what they do (I don't have much knowledge in electronics), but that doesn't look good. Could they be the cause of the failure ? Or maybe the symptom of something else ?
I can read "CEC P09" on them.

I'd really like to fix that HDD because I think some very useful software may be inside it (I'm talking about it further in the post).

Also, its floppy drive, a Mitsumi D359T2, doesn't work : the heads aren't moving, but the spindle spins. Other floppy disk drives work though, but I'd rather keep the original one in.

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I've attempted to lubricate the rails and the stepper motor's worm, but it didn't help much. When I turn on the computer, I feel the that the worm is moving slightly indicating the stepper motor can still do something, but it doesn't spin at all. I heared it spin once and it made a terrible sound. But now even during the seek test I don't feel like it wants to move.
Bad motor or rather bad controller card on the drive side ?

Then, there's also the DALLAS battery that of course has died and worse it's soldered in.
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Fortunately, I have the right tools to treat that properly 😁

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I'll drill through it to attach a battery holder later. But at least now the desoldering task is finished.

However there's a much bigger issue related to this ... The computer asks me to configure it using a program named "SETINIT.EXE". But I can't find this anywhere ... There's little information about this computer online (not even a picture of it), and it seems some people have asked about this back in the early 2000's, but I couldn't find any good answer ...
This is why I'd like to fix the HDD, I think this program could be inside of it.

Can anyone help me ?

BONUS
Here's how late this 8088 clone is :
NWr8QUrl.jpg
1991 😮

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Reply 1 of 26, by Horun

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Those old 720k floppy drives have a few electrolytic caps in them and should be replaced.
Dead floppy drive? Need a 2nd opinion
As far as the old HD's have never had any good luck fixing the controller boards or if they did work after fixing it was not for long. Motor bearing or platter issues soon followed.

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.

Reply 2 of 26, by Deksor

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I thought about this (this is a 1.44MB drive though), but if you pay attention, the caps are all located on the second board, not the one where the stepper motor is connected to (and I've looked on the other side and there are none). Now maybe that's the problem, but that doesn't seem to make much sense to me.

I may end up swapping that drive afterall, finding an identical one shouldn't be too hard.

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Reply 3 of 26, by Projekt2501

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OMG. This is the first PC I ever owned and as knowing nothing at the time (I as 11 at the time) we didn't realise how poor a specification this PC had. (An 8088 cpu in 1991!)
My father bought it and it came as such:
8088 cpu
640k RAM
Built in VGA graphics
NO Sound card (only PC speaker-I added a Disney Sound Source)
1.44mb Floppy disk drive
NO HDD - had to boot into DOS with Floppy
NO Mouse (added a serial one later)
NO windows (Only Deskmate - 7 Floppy disk 'OS' with limited functionality)
A Good Colour Monitor
I added a joystick card afterwards.
Epson Dot-Matrix

Reply 4 of 26, by Deksor

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Nice ! Do you remember how the bios setup was accessed ? Or do you still have the setup disks around ?

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Reply 5 of 26, by weedeewee

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Deksor, if the bios is available online (hint hint) someone could dive into it and figure out what data is expected to be found inside of the dallas chip, which port it is located on and a simple program could be written to get the required data back into the dallas chip.

Did you ever get the hard drive working again ?

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Reply 6 of 26, by Deksor

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Sadly no, I haven't found any identical HDD from which I could steal the pcb

However I made a strange discovery when looking inside the bios ROM : there are signs of a BIOS setup.

However the computer doesn't let me access it in any way, it asks for a setup disk.

Now I'm quite confused.
Did Tandy take an ami bios (that's what it is) and disabled the integrated setup ?
Was this by (bad) design and the setinit program could be resumed as a debug command ?

This needs more investigation but I'm not sure I can do that.
I tried to run debug to run code at the offset the setup seems to start but that didn't work 😒

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Reply 8 of 26, by Deksor

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Whoops, sorry, you can download it here https://www.ultimateretro.net/en/motherboards … 10766#downloads

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Reply 9 of 26, by weedeewee

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odd things, the bios seems to have the option for english franch 😁 and german, yet I find only english and french text. no german.

Just noticed, the mainboard uses the acer m1101 chipset. I think that's the same one as my old xt board has, which is a rebrand of ... i forgot... probably some UMC chip, yep umc 82c088
it can switch between turbo & xt frequencies by writing to a specific port if memory serves me right. and without loading the keyboard driver, if the bios supports it, should be able to switch using ctrl-alt-numpadminus or plus .

Here's to hoping predator99 can figure out which port the dallas chip is on and what the checksum and other entries ought to be.

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Reply 10 of 26, by Predator99

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I took a look at the dump. The 1st half is a Video ROM. The 2nd half is the system BIOS.
It runs in PCem in the "Atari PC3" machine.

It loads XT-IDE but doesen detect a HD (this should be fixable on a real PC..). It boots DOS from floppy.

So whats the issue you actually have? Doesnt your PC boot at all? I think you can also try a generic XT BIOS like
https://www.phatcode.net/downloads.php?id=101

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Reply 11 of 26, by Deksor

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The problem I have is that I can install things on the HDD, but I can't boot from it, and I'd like to access the CMOS setup because I'm curious what settings I can mess with in there (That'd also let me get rid of the message "Run SETINIT.EXE" at POST)

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Reply 12 of 26, by Predator99

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So you can boot DOS from floppy and access the hard disk as C:?

Adding a XT-IDE Bios on a network card should fix this?

I am not sure if the CMOS setup is really implemented in the BIOS. Yes, the strings are visible. I will try to check this. But you can also see
"720 KB 3?", 1.44 MB 3?", Not Installed Options:"
"German : Select German"
I dont think a 1.44 MB floppy is supported. There also no further german strings inside...

It seems CMOS is configured exclusively with SETINIT.EXE. Therefore I dont think it can be done within the BIOS, too.

Reply 13 of 26, by Deksor

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It *does* support 1.44MB floppy

Using XT ide would probably work, but that doesn't feel right, because the main bios should be capable of this too 🙁 (and other things such as the RTC don't seem to work properly)
This bios is so weird.

Also I don't think I'd even need a NIC for XT-IDE if I wanted : there's a second ROM socket, and the socket the ROM is in can fit bigger ROMs, so I wonder if I couldn't just put a larger ROM and it'd work as well ?

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Reply 14 of 26, by weedeewee

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Deksor, from my experience with my xt board with an m1101 chipset, the second rom socket, on my board, was mapped to where the BASIC rom is supposed to be

getting rid of the SETINT message would imply figuring out where it reads the RTC ram and maybe does some checksum calculation, then figuring out how to write a good checksum back into the RTC ram.
ergo which port the rtc is located at on the XT, you could also do this with a logic analyzer hooked up to the nwx287 AD & AS pins
or using something like unpc to read all the io ports and look where the data resembles RTC registers.

Goodmorning !

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Reply 15 of 26, by Predator99

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I took a look at the BIOS...:

At the beginning it does this:

F000:E015 BB00A0        MOV	BX,A000                            
F000:E018 8EDB MOV DS,BX
F000:E01A 32FF XOR BH,BH
F000:E01C 813F55AA CMP WORD PTR [BX],AA55
F000:E020 7406 JZ E028
F000:E022 813F4D46 CMP WORD PTR [BX],464D
F000:E026 7505 JNZ E02D
F000:E028 EA080000A0 JMP A000:0008
F000:E02D FC CLD
F000:E02E 8CC8 MOV AX,CS
F000:E030 8ED0 MOV SS,AX

Doesnt make much sense to me: It looks if there is a ROM at A000:0. If yes, there is a jump to it? Thats where the Video RAM should be?

All these error messages are printed here:

F000:8487 B402          MOV	AH,02                              
F000:8489 32E7 XOR AH,BH
F000:848B 7404 JZ 8491
F000:848D 81CD8000 OR BP,0080
F000:8491 B028 MOV AL,28
F000:8493 E680 OUT 80,AL [b]+++POST Code 28 [/b]
F000:8495 F7C50020 TEST BP,2000
F000:8499 7408 JZ 84A3
F000:849B BEF185 MOV SI,85F1 [b](CMOS INOPERATIONAL) [/b]
F000:849E E8FD40 CALL C59E
F000:84A1 EB48 JMP 84EB
F000:84A3 F7C51000 TEST BP,0010
F000:84A7 7406 JZ 84AF
F000:84A9 BE9B86 MOV SI,869B [b](CMOS checksum failure) [/b]
F000:84AC E8EF40 CALL C59E
F000:84AF F7C50800 TEST BP,0008
F000:84B3 7406 JZ 84BB
F000:84B5 BE1F86 MOV SI,861F [b] (CMOS battery state low) [/b]
F000:84B8 E8E340 CALL C59E
F000:84BB F7C50400 TEST BP,0004
F000:84BF 7406 JZ 84C7
F000:84C1 BED286 MOV SI,86D2 [b] (CMOS time & date not set) [/b]
F000:84C4 E8D740 CALL C59E
F000:84C7 F7C58000 TEST BP,0080
F000:84CB 7406 JZ 84D3
F000:84CD BE5287 MOV SI,8752 [b](CMOS floppy type mismatch) [/b]
F000:84D0 E8CB40 CALL C59E
F000:84D3 F7C54000 TEST BP,0040
F000:84D7 7406 JZ 84DF
F000:84D9 BE1187 MOV SI,8711 [b](CMOS dispyal type mismatch) [/b]
F000:84DC E8BF40 CALL C59E
F000:84DF F7C52000 TEST BP,0020
F000:84E3 7406 JZ 84EB
F000:84E5 BE5786 MOV SI,8657 [b](CMOS system options not set) [/b]
F000:84E8 E8B340 CALL C59E
F000:84EB B029 MOV AL,29
F000:84ED E680 OUT 80,AL [b]++++Post Code 29 [/b]
F000:84EF C606720000 MOV BYTE PTR [0072],00
F000:84F4 E85F5B CALL E056
F000:84F7 81E5FFBF AND BP,BFFF
F000:84FB 55 PUSH BP
F000:84FC 81E5FF1F AND BP,1FFF
F000:8500 5D POP BP
F000:8501 742F JZ 8532
F000:8503 E8505B CALL E056
F000:8506 F7C5FC00 TEST BP,00FC
F000:850A 740A JZ 8516
F000:850C BEA587 MOV SI,87A5 [b]Run SETINIT program [/b]
F000:850F E88C40 CALL C59E
F000:8512 81CD0040 OR BP,4000
F000:8516 BE9585 MOV SI,8595 [b]Press a key to boot [/b]
F000:8519 E88240 CALL C59E
F000:851C F7C50020 TEST BP,2000
F000:8520 7509 JNZ 852B
F000:8522 B03F MOV AL,3F
F000:8524 E81140 CALL C538
F000:8527 3CA5 CMP AL,A5
F000:8529 7407 JZ 8532
F000:852B B400 MOV AH,00
F000:852D CD16 INT 16
Show last 1 line
F000:852F E8245B        CALL	E056    

However, the actual check is not done here. It depends on the content of BP which error message is printed. And this is loaded somewhere else...
You can also see not all text thats inside the ROM is used.

Reply 16 of 26, by Deksor

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This is weird because I definitely have french messages on my screen. Your screenshot has one too ! Unless you mean that some french messages appear and some don't ?
Maybe the ROM is shadowed and modified in memory ?

Considering this is a 1991 XT bios and what we can see in this ROM, to me it feels like it was rushed (They probably didn't put too much money into making such a machine, because who would buy a new XT machine in 1991 except someone that didn't have a very large budget ?)

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Reply 17 of 26, by Predator99

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Indeed, I noticed my mistake as I noticed my screenshot above: In the dump there is always the english message and next to it the identical one in french. Both are printed...

Shadow in a Xt..? Dont think so. Maybe A000 is the location of the 2nd ROM socket. But thats where the VGA-RAM should be...

But also interesting is that the Video-ROM is in the 1st half of your ROM dump. Therefore it should be mapped to F000:0. Cant check in PCem if its really there because I had to delete this part to get it running. BIOS-ROM starts at F000:8000.

Reply 18 of 26, by Deksor

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I guess I could check this with some debug-fu on my machine ?

Shadow in a Xt..? Dont think so. Maybe A000 is the location of the 2nd ROM socket. But thats where the VGA-RAM should be...

Well I know it's uncommon, but everything in that machine is uncommon so that may not be entirely out of question ^^

Maybe I should try some VGA program to make sure VGA works

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Reply 19 of 26, by weedeewee

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Here I am looking at the code, wondering why that OUT 80,AL looks so familiar.
then it hits me, duh, post codes 😋

would it be possible, with some glue logic in hardware to map the first part of the rom to A0000 and the second part at F8000 ?
I guess it would only be one bit that needs to flip at the right time.

but

I'm more interested in what gets done before those error messages get printed.
Which IO ports gets read that might be read from the RTC and see what gets done with the data. reverse engineer what the SETINIT should do.

Right to repair is fundamental. You own it, you're allowed to fix it.
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Do not ask Why !