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Testing/Repairing ST's

SiriusHardware

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It's really up to Nicolas what he chooses to do with a machine which belongs to him, I support his decision to leave the mod well alone since it does not change the 'normal' behaviour of the machine. I myself would probably remove it because once something belongs to me it stays in my possession. I prefer machines to be as nearly original as possible and I definitely don't like them cluttered up with obscure mods like this even where I understand their purpose.

One thing I would always leave in place would be an aftermarket memory expansion, since that is clearly a generically beneficial mod. I might, however, tidy it up or source and fit a neater version of the same thing.
 

SiriusHardware

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A couple of suggestions about the broken, possibly cut Tantalum on the overscan-mod - first of all it may actually be faulty, and that would be why it has been 'removed' from circuit - if it is just one decoupling capacitor of many across the 5V supply then removing it probably won't make much difference. However I tend to think that anyone who had traced a fault to that precise component and clipped it open circuit to clear the fault would then have replaced the faulty capacitor. To be sure, with one leg of the capacitor already disconnected it should be easy to check the capacitor itself for low resistance or a short.

However, my feeling is that most technicians, having traced a fault to a specific component, would replace the faulty component rather than leaving it disconnected.

It should be simple enough to determine whether this is just a supply decoupling capacitor, meter continuity from each of the leads (one still attached to the capacitor, one snapped off it) at the PCB end, and you should find that one has a direct connection to +5V and the other has a direct connection to 0V.
 

Nicolas 2000

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Thanks for the input! When I (ever) dive in to replace the dying/dead/zombie supply caps, I'll have a look at the overscan circuit as well to see what's going on.

My quest to understand/get the overscan circuit to run isn't helped by the Atari forum being insecure according to my browser and being unable to register as the Atari forum thinks I'm a spammer... But through it all, I've been able to at least download an overscan.prg driver. Not that I currently have any software that would benefit from overscan, apart from perhaps just the basic GEM desktop. :) And then there's the thing that I don't know yet how I can create a floppy which has this overscan.prg in an AUTO folder. I've only been able to throw entire disk images onto floppy. Maybe if I can get the prg onto the floppy I could move it into a new AUTO folder via GEM... But I think my Windows floppy creation software also allows for file transfer so I might be able to do it through there.
 
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SiriusHardware

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That's odd about the problem with Atari-Forum, my browser here from work is also complaining that there is a problem with the site's security certificate. I haven't noticed any problems from home but I will look at it tonight. I have been a member on that forum for years without any problems. You may be unlucky enough to have an email from a domain from which a lot of SPAM has recently been sent. Like most forums these days, even if you register OK your first few posts will be moderated to try to screen out SPAM bots.

A small tip about Atari STs and floppy discs, early TOS versions used a proprietary disc format which was just different enough from the standard DOS format to be a nuisance but by TOS 1.4 (often called the 'Rainbow TOS') Atari had made TOS able to read / write standard DOS 360K / 720K formatted discs, so if you can prepare one of those on some other PC and make an AUTO folder and put your driver .PRG into the Auto folder that should work in the Atari.

Note that I said 360K / 720K though, NOT HD, ie, not 1.44MB discs. The 'biggest' drive any standard ST came fitted with as standard was 720K, as far as I know. The disc really has to be a 360K or 720K disc, not a HD disc formatted as 720K because although that might sometimes work it generally doesn't work very well - so - old 720K discs (same as Amiga?) are best to try for this.
 

Nicolas 2000

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My STFM has rainbow TOS.

I still had some DS DD floppy's lying around from my 386 days, but they pretty much died upon writing them for the Atari. I also still had quite some 1.44 discs from those 386 days. Tried them out with a taped up hole, and they worked on the Atari. So lacking the correct media, I'll try that trick again for making an Overscan disc.

I have a pile of DS DD floppy's for the Amiga, but as those contain as yet untested Amiga software, I'm letting them be for the moment.

It's good to know that Atari can read DOS formatted discs. One way or another I should be able to make the disc using ye olde Pentium4 XP PC. I'm curious whether that Overscan mod actually works!
 

SiriusHardware

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When Rainbow TOS (or later) formats a floppy, it formats it as a DOS format FDD, so maybe try formatting the discs on the ST before putting them into a PC and copying whatever you need onto them. For this to work the discs obviously MUST be SD 360K or DD 720K because the Atari firmware / hardware doesn't 'know' what an HD disc is. I think some very late versions of TOS (V2.xx) may properly support high density (1.44MB) drives, but you'll have to research that. My guess is that you won't be looking to change the TOS version on this machine anyway.
 

Nicolas 2000

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I'm not hardcore into Atari anyway. I just happen to have three ST's as collateral damage. :) But as this one turns out to be quite pimped out, I'd like to see if all those goodies actually work. And who knows, I might keep one of the ST's even though I've yet to find a reason for me to keep one next to an Amiga.For the moment, it's an enjoyable learning experience as I've never used an Atari before.

So I've got a rainbow TOS and I see six (replaced?) TOS ROMs on the mainboard. I don't know anything else about which version(s) I have. I'll see if I can create a Sysinfo disc so I can also check the RAM upgrade. But the current TOS works and if it's broadly compatible, the current TOS will do for me.

I'll try your plan of action with the discs when I continu my experiments.
 
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SiriusHardware

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TOS 1.4 is generally held to be the best all round TOS for 'legacy' use although there were a few early game titles which used unsanctioned methods of reading system information directly from where they were held in system variables, only for those variables to be moved to another location in later TOSes, which broke some of those early titles, for example Arkanoid (Breakout clone) where the original release read the mouse 'x' position directly from a particular RAM location instead of politely asking the OS for it. If you try to run that release on a later TOS the game runs but the 'ship' won't move left or right, so you don't survive for very long. (Later releases of 'Arkanoid' fixed this).

Some TOSes only work on certain hardware anyway, for example TOS 1.6 (or 1.06?) is STe- specific.

There are some decent games which have 2-player modes which are cross-format RS232 linkable ST-to-Amiga, for example STUNT CAR RACER where one player can be on an ST and one on an Amiga.
 

Nicolas 2000

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That actually is a good reason to keep a second system around! I only have one monitor at the moment, but anyway. I'll hold onto at least one Atari for the time being. If it all works that just might be the pimped out one. Apparently it also works with Lotus Turbo 2.
 

1ST1

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I'm not hardcore into Atari anyway. I just happen to have three ST's as collateral damage. :) But as this one turns out to be quite pimped out, I'd like to see if all those goodies actually work.
Yes, it has AutoSwitch-Overscan, and it has memory extension. That is definitive a machine which has been expanded not for gaming, but for serious work. To profit from that you need a hard disk or a flash based alternative (UltraSatan, CosmosEx, ...) to be able to install the Overscan driver and to start applications which need more RAM as program-code/data can be loaded from one floppydisk and which can profit from the extended resolution. Some people would be jealous to hear that you have such a machine and use only for gaming and they have to try to find these extensions and integrate by themselves.
 

Nicolas 2000

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I've managed to load Sysinfo onto one of the few 1.44MB discs (taped off) that this Atari eats. I first tried another one, but that was faulty.

Sysinfo tells me I have a regular 68000@8MHz, no surprise there. TOS 1.04. No surprise there. 06-04-1989. Blitter and a few others not available, is that normal for an STFM?

Also, do I read it correctly that the 4MB expansion appears to work?

Next, Overscan. I read in an Atari magazine review that you are supposed to put Overscan.PRG into the AUTO folder of a floppy disc. I didn't have the VIDEO50.PRG but I think my ST boots in 50Hz color mode anyway.

When I boot with the floppy disc in place or run Overscan.PRG from GEM, I get "Overscan Version 1.6. NOT activated."
I don't see any overscan magic in GEM. I have no real background from this PRG; maybe it is from an Overscan that had the manual switch? Or I'm doing something wrong, or there's something wrong on the hardware level. I'm stuck here.
 

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Nicolas 2000

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Aha, I've made it onto the Atari forum. It seems I downloaded an incompatible Overscan driver earlier. I'll try again with the one I found now.
 

Nicolas 2000

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I've downloaded the other Overscan driver ZIP, which was labeled as belonging to AutoSwitch Overscan and contained a nice AUTO folder. Managed to create an empty disc with said AUTO folder, and...ta-dah!

Good to know that if I ever plan on doing anything that can use the extra screen space, it's there.

OK next for this Atari ST quest is waiting for the SCART cable to arrive to test the (seemingly bone stock) 1040STF. Then maybe fabricate a supply and test the 520ST+. Perhaps build a null modem as well. I just realized I couldn't get Stunt Car Racer to run on the STFM. Bad disc, bad image? No idea. I'll try again later with a different image.

Edit: tried with a different image, Stunt Car Racer now works perfectly. And impressively smooooth.
 

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SiriusHardware

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Nice to see that working.

Regarding discs and specifically 1.44MB discs, although you can make one 'look' like a 720K floppy by covering the 'type' window there is also a difference in the type of magnetic material used on the disc surface. A disc which you create on a PC and read on the Atari will probably work well enough because it has been written by a PC whose disc drives are fully compatible with HD discs, but you may hit problems when you try to write to the disc from the Atari. Some games reserved a section of the original disc for saved games and will try to write to the original disc rather than prompting you for a saved-game disc and might run into problems at that point. There is no harm in trying though, if you can just make another clean copy of the disc with a PC.

I have a working copy of Stunt Car Racer (ST) here, but I am sure you will find one which works lying around on the internet somewhere. There are rare cases where having extended memory will actually STOP a game from working, possibly due to a poor / incomplete method of checking how much memory the ST has. I don't think original STs (not counting the Mega ST / Mega STe) ever came with more than 1MB, although it was common for people to fit third party memory expansions taking the memory up to at least 2.5GB. The STe can be expanded to 4MB by replacing its original memory SIMs.

The Atari ST emulator 'Hatari' is a good way to test software's ability to run on various combinations of machine and memory size, assuming you are finding your discs in the form of .ST disc image files, which Hatari is able to 'load'.

Possibly the best 2-machine link game I ever played (on two STs as it happens) was the F15 combat flight sim 'F15 Strike Eagle II'. This had a really radical (for the time) 2 machine linked player co-op mode which allowed the 2 players to be the pilot and 'wizzo' (Weapons Systems Officer) respectively of a single F-15, so you and your buddy would be flying as the two man crew with the 'Wizzo' handling all the real time stuff that the pilot was too busy to do when the mission parameters were turned up to high difficulty. Shades of Top Gun. It was produced, as most of the best combat sims were, by Microprose.

The Blitter is not standard fit on an ST / STFM but it comes built into the STe.
 
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Nicolas 2000

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Your reply just crossed my edit that I've got stunt car racer working now. I'll check out F15 in due time, thanks for the tip! Old time Falcon 4.0 abuser here.
 

1ST1

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Sysinfo tells me I have a regular 68000@8MHz, no surprise there. TOS 1.04. No surprise there. 06-04-1989. Blitter and a few others not available, is that normal for an STFM?
Yes, that is normal and the memory is detected as well.
When I boot with the floppy disc in place or run Overscan.PRG from GEM, I get "Overscan Version 1.6. NOT activated."
You found it by yourself, you have to start it before the desktop is started, otherwise it can not install/enable it. AutoSwitch Overscan is even more powerfull in monochrome monitor, you allmost get 800x600, to be exact, up to 762x576.

Don't use 1.44 MB diskettes, try to get 720kb disks. 720kB floppy drive read/write head have too small magnetic fields to read / write HD disks reliable. There is a different between DD and HD disks, it is not only that hole in the plastics, but also the sensivity of the magnetic surface of these disks. And if you format such a PC which is using HD drive, it also confuses the floppy controller of the PC. These drives have a switch, and HD disks have a hole, and that hole opens that switch and tells the floppy drive and floppy controller that there is a HD diskette. So the system will write with 16 MHz data clock, while 720 kB is 8 MHz only (double clock, double capacity). At least you have to close the hole with tape, but as then the floppy drive swichtes to 720 kB it only uses lower magnet field to read/write the disk, and again, that written signal is too weak to be reliable. Example, a few weeks ago I got another 520ST+ with a box of 50 diskettes, the real 720kB diskettes all were readable with allmost no problem, but those 20 years ago last time written HD disks all were unreadable, but just after reformatting them on a PC as HD disks they were fine again (but not readable in a standard ST with 8 MHz only floppy controller).
 
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