260ST barn find

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BenTennyson
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260ST barn find

Postby BenTennyson » Sun Apr 15, 2018 7:31 pm

Hi folks.
I'm new around here and to everything Atari in general. I was a Commodore kid back in the days so I've got NO prior knowlegde whatsoever, so please bear with me when I seem to ask stupid questions. I already read up on some topics, but still need confirmation on some things.

I only know the name Atari from stupid religious fights with school mates and the brother of a friend, who used his in an audio workstation setup.

So I've been gifted this 260ST by a friend and I saw this as a chance to enlarge my small world view and try to get this thing up and running, since I'm into retro computing anyway. I currently own a C16, C64, an Amiga 500 and 1200. Oh and a crusty Schneider EuroPC that hasn't seen an outlet for at least 15 years.

So the problem with this Atari is that it came with NOTHING. I already have a solution to power it by means of a spare ATX power supply. And I presume I could hook up my Commodore 1084S at least for low resolutions right? Will the graphical user interface run on lo-res as well?
I also have enough Amiga mice to sacrifice one for a re-wiring surgery.

I think the biggest two problems I'll face will be that I have no disk drive or kickstart disk (whats the kickstart called in Atari lingo?), since the 260 doesn't have a ROM, correct? What is the difference between TOS and GEM by the way, can you call it the equivalent of kickstart and workbench? Is both integrated in the later ROM models?

Can I somehow connect a shugart interface floppydrive to this model without an SF314 case?

Thank you for your patience and for making it below that wall of text :coffe:

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Re: 260ST barn find

Postby troed » Sun Apr 15, 2018 8:56 pm

Congratulations :)

Your 260ST might or might not have a full TOS (operating system) including GEM (graphical user interface) - else it only has a boot rom which will load TOS from disk. You will be able to replace the boot rom chips with a full TOS if so.

Regarding Shugart interface, how handy are you with building stuff? There's a somewhat easy way of creating an internal 34 pin connector in that model (all non-F models) - but requires lots of soldering and wiring. Else you can still find external drives (SF314 and clones) to buy.

The following photos will form part of an extended writeup I'll do over att exxos' forum when I get the time, but I think you get the gist. What's not visible is the wiring converting from the 12 solder pads to Shugart 34 pin, but the (in progress) Eagle schematic shows the thinking.

floppy1_small.JPG


Note: Some motherboard models have filters instead of zero ohm links here. In that case they need to be desoldered and then put back on top afterwards, and all three rows of pads need to be wired up (as shown in the schematic)


floppy2_small.JPG


floppy3_small.JPG


floppy4_small.JPG


floppy5_small.JPG


floppy_schematic.png


(DS0/DS1 extracted to their own pads instead of just wired through since I'm building an internal HxC slim and want to be able to switch between it being A: or the external drive being A: .. )
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Re: 260ST barn find

Postby BenTennyson » Sun Apr 15, 2018 9:24 pm

Great news, thank you. So do I interpret that correct that the external floppy case has no own logic components aside from the floppy itself?
Concerning my building abilities...
I'm certainly no master, but I learnt proper soldering techniques in my job training, and made the occational hardware mod here and fix there.
What I totally suck at really is building or modifying cases etc, especially concerning plastics. I think I might use your instructions but keep my drive outside the Atari for starters.

I just opened up the 260 and holy moly it looks freaking terrible...
I see no rust or corrosion on the first glance, but it is full - really full of dust, brick dust and something that looks like powdered chalk. Along with the obligatory barn smell.
Cleaning that up will take quite a while.
https://imgur.com/a/PNaCp

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troed
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Re: 260ST barn find

Postby troed » Sun Apr 15, 2018 9:37 pm

You have a memory upgrade there! :) Not fully populated either. That's great news (as I alluded to over at Reddit).

edit: Yes. you got that right. The Atari talks Shugart, just over 14 pins in that external connector instead of 34. It's just wiring.

http://info-coach.fr/atari/hardware/int ... _Connector

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Re: 260ST barn find

Postby BenTennyson » Tue Apr 17, 2018 5:52 am

Eew I'm glad I didn't just power this up before opening.
I don't really wanna know what that fluffy stuff is.
Also, this MMU PCB popped right off the socket when I touched it:
Image

It looks like this machine is populated with TOS1.4 roms, according to the stickers:
Image
Note that I put the green tape on the rom chips myself since they have a transparent lid, I presume they are the light erasable types.
Doesn't look pretty, but I've never handled these before and I am afraid to accidentaly erase them.

I cleaned the whole machine by now, the PCB looks fine but the bottom shield has some rust on it, which bled onto the inner plastic housing.

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Re: 260ST barn find

Postby BenTennyson » Sat Apr 21, 2018 2:29 pm

troed wrote:You have a memory upgrade there! :) Not fully populated either. That's great news (as I alluded to over at Reddit).

edit: Yes. you got that right. The Atari talks Shugart, just over 14 pins in that external connector instead of 34. It's just wiring.

http://info-coach.fr/atari/hardware/int ... _Connector


I am hesitant to do internal modifications to this machine so I rolled up my sleeves and typed till my fingers were sore and turned up three different resellers to obtain 7-, 13- and 14-pin plugs on EBay. Its the ONLY place I could find a 14-pin plug, a reseller from the UK.

According to your post, and to these links
-> http://info-coach.fr/atari/hardware/interfaces.php#Floppy_Disc_Connector
-> http://www.hermannseib.com/english/synths/ppg/wtfloppy.htm
it should be possible to wire a standard shugart floppy cable to the 14pin Atari jack like this:

Code: Select all

   Shugart 34              Atari 14-pin DIN
1,3,5...31,33   Gnd      3,7
         2       DENSEL       Since the WD1772 doesn't support High Density, where does this go? This is (D)isk(C)hange on Amiga...
         4       INU                  Not connected??
         6       DS4                  Not connected??
         8       IDX                  Pin 4
       10       DS1                  Pin 6(?)
       12       DS2                  Pin 5(?)
       14       DS3                  Not connected??
       16       MOT                  Pin 8
       18       DIR                  Pin 9
       20       STP                  Pin 10
       22       WD                  Pin 11
       24       WG                  Pin 12
       26       TK0                  Pin 13
       28       WP                  Pin 14
       30       RD                  Pin 1
       32       SS                  Pin 2
       34       RDY                  Not connected??

According to my knowledge, TOS needs the Diskchange signal, but how would that even work? No more free pins.

I presume you couldn't use pop in an Amiga nor a PC floppy drive totally unmodified?
I really like your work on the internal connector.

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Re: 260ST barn find

Postby troed » Sat Apr 21, 2018 2:57 pm

This is from my own notes when making this mod:

Code: Select all

2 => (density select)
4 = n/c
6 = n/c
8 <= /index
10 => drive 0 select
12 => drive 1 select
14 => (drive 2 select)
16 => /motor on
18 => /direction in
20 => /step
22 => /write data
24 => /write gate (floppy write enable)
26 <= /track 00
28 <= /write protect
30 <= read data
32 => side 0 select
34 <= (disk change/ready)


== 12 signals used to connect. 2, 14 and 34 can be left unconnected for an HxC slim at least. If that doesn't work, try grounding 2 and 14

The Atari doesn't use a specific disk change signal, but checks the status of write protect changes.

Many PC drives work fine as long as you change their default from DS1 to DS0.

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Re: 260ST barn find

Postby Foxie » Sat Apr 21, 2018 6:11 pm

Reminds me of this Amiga barn rescue: http://www.amiga.org/forums/showthread.php?t=71237

Your thinking is pretty much right, TOS = Kickstart and GEM = Workbench. Except GEM also contains the code to manage windows, while Workbench relies on code in ROM to do that. Unlike the Amiga, TOS and GEM are never separated - you either load both from disk on the oldest models, or both are in ROM.

I'm sure a 1084 will work fine on the ST. I've used my Atari colour monitor on the Amiga without any problems. The 13 pin monitor port has R/G/B, composite sync and separate H/V sync. The user interface works in all three resolutions, but some productivity software (like Cubase) needs a high-res monitor. High res mode is pretty much just VGA, so you can use any IBM monitor. The video output appears on the monochrome pin, which you need to wire to R/G/B on the IBM monitor. There's also another pin which you connect to ground for the Atari to detect a high-res monitor.

Transferring programs to floppy is easy. It's just an MS-DOS format FAT12 disk, you can use an IBM to write the disk. Of course it needs to be formatted double density.

I have heard of some people experiencing problems with TOS detecting disk changes when using an IBM drive. I don't know all the details, but I think some drives behave different with their write protect signal when the disk is removed? A logic gate would fix that, if required.

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Re: 260ST barn find

Postby BenTennyson » Sat Apr 21, 2018 6:51 pm

troed wrote:This is from my own notes when making this mod:

Code: Select all

2 => (density select)
4 = n/c
6 = n/c
8 <= /index
10 => drive 0 select
12 => drive 1 select
14 => (drive 2 select)
16 => /motor on
18 => /direction in
20 => /step
22 => /write data
24 => /write gate (floppy write enable)
26 <= /track 00
28 <= /write protect
30 <= read data
32 => side 0 select
34 <= (disk change/ready)


== 12 signals used to connect. 2, 14 and 34 can be left unconnected for an HxC slim at least. If that doesn't work, try grounding 2 and 14

The Atari doesn't use a specific disk change signal, but checks the status of write protect changes.

Many PC drives work fine as long as you change their default from DS1 to DS0.

Thanks for clarifying. Now I just have to anxiously await the arrival of my DIN-jacks :)

Foxie wrote:Reminds me of this Amiga barn rescue: http://www.amiga.org/forums/showthread.php?t=71237

Eww seeing these pictures, I presume I got really lucky with mine.
Foxie wrote:I'm sure a 1084 will work fine on the ST. I've used my Atari colour monitor on the Amiga without any problems. The 13 pin monitor port has R/G/B, composite sync and separate H/V sync. The user interface works in all three resolutions, but some productivity software (like Cubase) needs a high-res monitor. High res mode is pretty much just VGA, so you can use any IBM monitor. The video output appears on the monochrome pin, which you need to wire to R/G/B on the IBM monitor. There's also another pin which you connect to ground for the Atari to detect a high-res monitor.

I've yet to decide how I wire my video cable, but since the 260 doesn't seem to have a composite signal, I'll propably go with a VGA-cable and a switch on that hi-res signal line.
Foxie wrote:Transferring programs to floppy is easy. It's just an MS-DOS format FAT12 disk, you can use an IBM to write the disk. Of course it needs to be formatted double density.

Are you sure about that? I have recently found many .ST and .MSA image files that are bigger than 720k (up to 880, in fact), which I can't seem to handle. I tried to write them to disk with Omniflop but although I am using an internal drive, not USB, and have installed both Ominflop drivers, every image above 720k throw an error message for some reason. Steem does read them fine, though.
Maybe the floppy controller on this specific board is not really able to pull this off.

Writing these images is propably much less prone for errors when writing them directly on the ST, but I will not put up with the transfer speeds of an RS232 connection. And hooking an SDCard reader to the ACSI looks like an adventure on its own. I know I will have to do that sooner or later but for now I'm glad when I have just some images for floppy to test if the ST works correctly. Lets hope for the best.

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Re: 260ST barn find

Postby Foxie » Sun Apr 22, 2018 8:16 pm

BenTennyson wrote:Are you sure about that? I have recently found many .ST and .MSA image files that are bigger than 720k (up to 880, in fact), which I can't seem to handle. I tried to write them to disk with Omniflop but although I am using an internal drive, not USB, and have installed both Ominflop drivers, every image above 720k throw an error message for some reason. Steem does read them fine, though.
Maybe the floppy controller on this specific board is not really able to pull this off.


I'm not sure what's going on there. Omniflop does claim to support 830K+ ST images but I've never tried it. The ST can't really do any special formats beyond just increasing sectors and tracks. It's not like the Amiga where you can have a completely custom disk encoding which the IBM can never read.

Do you know of any Amiga programs which can write a raw image to a floppy? You might have better luck with that.

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Re: 260ST barn find

Postby BenTennyson » Tue Apr 24, 2018 3:48 pm

Nah, all I have and know is ADF2DISK, I didn't try that with non-Amiga formats yet.

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Re: 260ST barn find

Postby iggydrougge » Fri Apr 27, 2018 11:10 pm

XadUndisk on Amiga handles both ST and MSA images.

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Re: 260ST barn find

Postby BenTennyson » Sun May 06, 2018 11:36 am

iggydrougge wrote:XadUndisk on Amiga handles both ST and MSA images.

Thanks for pointing this out. I prepared my Miggy and will try to write the culprit images as soon as I got this Atari up and running.

~

My makeshift Power Supply is finished. I just butchered an Amiga 500 PSU and soldered an Atari PSU plug to the cord.
Now I decided to produce a "link box" for this 260, which has a floppy drive as well as video and audio connections built in (Scart+VGA9). I strongly like to throw in a composite signal and wondered if its possible to hook up a Commodore A520 to the Atari ST260. I had one spare so I ripped the PCB out of its case and cut away the whole TV Modulator part. To be sure I hooked it up to my A1200 and of course it still works (grabbing the Composite signal at R24).
This modulator needs 5v and more juice on the 12v line than the Atari can deliver on the video port, but that doesn't matter since this 'link box' needs a direct connection to the PSU for the floppy drive anyway.


Now verifying the Amiga RGB23pin port and the Atari port, it seems like the Modulator needs an external clock source on Pin 15 of the RGB port, which the 260ST doesn't seem to provide (just guessing, since that pin is connected to IC2). I don't quite get why it would need that, since it has its own 4Mhz Oscillator.
If any one of you understand more about these things, please take a look at the specs of the A520, the Commodore RGB23 port and the Atari Connector and please give me a hint how to proceed. I don't just want to randomly poke around and risk frying the A520 or worse the Atari.

Also, info-coach.fr says, that Composite Synch is "only available on the STE". If the 260 doesn't provide that either, it should be possible to generate a Composite Synch signal from Hor And Vert Synch (Pin 9+12), no?

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Re: 260ST barn find

Postby BenTennyson » Thu Jul 05, 2018 9:30 am

Just a small update - I didn't sort out much else but this one:

The MC1377P video encoder IC used on the Commodore A520 needs an 4.43Mhz sine (or square, as seen in the original schematic of the A520) wave on pin 17 for the color subcarrier.
The original design was using a clock provided by the Amiga for genlocking purposes. The MC1377P comes with its own on-chip oscillator, you just have to add three caps and re-use the onboard crystal like in the following schematic:

https://i.imgur.com/fK5pL71.png

Built and tested successfully on an A1200+1084S setup.

In theory it should run on an Atari 260ST like this as well.
I should have read the FULL datasheet of the MC1377P sooner :roll:


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