New Owner of Modified Mega ST2s - Hmmm

[game_player_s]

For starters I have never before owned any Atari Computer. Not for lack of interest mind, just the whole run of them are as rare as hens teeth in my area.

 

Apology in advance for the lack of pictures, will try to rectify that aspect sometime tomorrow. Basically I've gone a good eighteen years of active video game collecting without entountering anything even related to a Atari computer. And then this past Saturday I found, and purchased, a odd pair of "Atari Mega ST2" computers at a estate sale. No clue if they work, no keyboard, no screws holding the covers on them, and both clearly have been modified from what a stock system should look like on the inside based on good pictures from one of the online computer museums. Again, will attempt to get some pictures taken and on here tomorrow.

 

Aside from the missing case/cover screws, one of the computers has no diskette drive, and is what I would regard as being a heavily modded motherboard. There are two chips on the board with hand written labels that read "TOS 2.06 High" and "TOS 2.06 Low". From what I gather via my crash course of these computers this is the integrated OS? But there are other chips that have been clearly added, mostly double and even a triple stack with wires soldered here and there. I have no idea what to make of this setup.

 

The second computer appears to be all there, again minus the case screws. From a brief look inside there appears to be a SIMM RAM expansion board installed, possibly more than that but 've not had the time to devote to giving it a more thorough go over just yet.

 

I managed to scrounge up just one odd looking video cable for the computers from the sale. I say odd as it comes out to a aluminum box which then has, what I presume to be, Stereo A/V RCA cables coming out and some strange looking ribbon cable. Any ideas as to what the ribbon cable is for, and/or am I wrong in thinking it is a stereo A/V output with the RCAs?

 

In a ideal world I'm guessing the cases would be scrwed together as intended for at least the sake of proper internal gounding, but maybe not? Anyone know if standard modern PC case screws are the correct size screws to use on these computers, and if not a source for replacement screws?

 

Also, I seem to have mixed info in regards to the diskette drive. The interface appears to be a standard IBM-compatible floppy connector, and the general consensus on the internet seem to be that any 2.5" 1.44 MB diskette drive is compatible, is that true or?

 

Again, I will work on getting pictures on here tomorrow.

Edited August 8, 2017 by game_player_s

[exxosuk]

TOS206 will likely have some adapter PCB as TOS104 is the max OS version which can be installed without modification.

 

Floppy drives you can use a 1.44 drive if you modify the drive select on the drive (tricky on anything but sony mpf series normally) but you wont be able to to use 1.44 floppies without more modifications to the motherboard.

 

You can normally find screws and RGB -> Scart cables on evilbay.

 

Probably best to take images of the insides to show whats going on better......

[ParanoidLittleMan]

Indeed pictures are needed - sharp, hi-res, if possible.

[game_player_s]

Well I have missed yesterday by about a half-hour. Posting pictures of the first Mega ST2 now, took forever to get all these cropped, so will be tomorrow (much later today rather) before I post pictures of the second Mega ST2. Here we go!

 

 

 

 

 

 

 

 

 

Edited August 9, 2017 by game_player_s

[game_player_s]

 

 

 

 

 

 

 

 

[game_player_s]

 

 

 

 

 

 

 

 

 

Hopefully twenty-seven pictures will suffice.

[exxosuk]

Serious hack job there. That will be some individual who has done that rather than any "offical" upgrade. Clearly TOS206 in there, some chips will be decoding. Also looks like its got some simple CPU speeder hacked in there also.

 

This is what my TOS upgrade and booster looks like. http://www.exxoshost.co.uk/atari/last/V22BOOSTER/index.htm So clearly not one of mine

[game_player_s]

Thanks for the reply exxosuk, so in your opinion would it even be safe to attempt booting that unit up?

 

And my apologies, it may be Monday before I can finish processing the pictures of the second Mega ST2 and the odd looking video cable box thing. Have been incredibly busy and entering into a rather busy weekend highlighted by an eleven hour workshift on Sunday.

[exxosuk]

You could try booting it, though I Would be surprised if it worked and was stable.

[game_player_s]

Second Mega ST2, amazingly, had a little zip-loc bag hiding under the diskette drive containing the case screws! So was able to screw it back together when all was said and done. And sorry for the delay in getting these pictures up. There's only one double-stack soldered in chip on this unit, which apparently I didn't get a very good pic of in regard to being able to read the marking of the chip (if interested I can take pictures again of it). The front of the case has a small rectangular hole that has been cut into it to the left of the make/model marking. Perhaps the hole was possibly intended for future use of add-in reset switch or some manner of activity LED?

 

 

 

 

 

 

 

 

 

Edited August 16, 2017 by game_player_s

[game_player_s]

 

 

 

 

 

 

 

 

[game_player_s]

And here's the close-ups I took of that double-stack chip. Also worth noting this expansion board is plugged directly into the Motorola 68000 CPU socket of the motherboard.

Also, it seems I failed to take a clear picture of the strange looking video output box thing, so shall try to get that done and posted here later this week.

 

 

 

 

 

And just for fun, a 1920x1080.:

 

Edited August 16, 2017 by game_player_s

[game_player_s]

I got two 3rd party product catalogs at the same estate sale as these two Mega ST2's and have been flipping through them this morning at long last. Closest thing I can find to this odd looking add-on board plugged into the 68000 CPU socket is in "Toad Computers: Product Catalog 3.42" (circa 1994), being a device with just a similar, not identical, illustration called a TT030 RAM Upgrade. There's definitely a 68030 CPU on this board, and definitely it has some manner of SIMM memory, so perhaps that is it? But then the expansion in question on page 36 of the catalog doesn't indicate nor specify inclusion of another CPU, rather the product description merely discusses that the TT RAM is compatible with ST machines.

[Umberto]

SST Manual.zip

 

SST, Awesome speeder. Gadgets by Small..

 

http://www.septicsurgeon.netSST Manual.zipSST_Driver disk.zip/Gadgets_By_Small_SST.html

Edited August 18, 2017 by Umberto

[+DarkLord]

Someone obviously had no idea what they had when they sold these.

 

You've scored big time my friend.

[Umberto]

Someone obviously had no idea what they had when they sold these.

 

You've scored big time my friend.

Ya he did

[game_player_s]

Someone obviously had no idea what they had when they sold these.

 

You've scored big time my friend.

It was a estate sale, so I'm pretty sure the previous owner has returned to the dust of the Earth. I mean you don't normally call in a estate sale company to purge the contents of a house unless the occupant has kicked the proverbial bucket right? And he had a lot of really neat stuff, and as a fellow member of the male gender of the human race I can't imagine parting ways with my stuff without a good reason. Not to say I haven't had to part ways with some fascinating articles of technology over the years, typically to fund car repairs, but this was a whole house and all contents kinda estate sale.

 

And thanks for identifying this upgrade doo-hickey thing-a-mcbobber Moonsweeper. That's a very fascinating read on the upgrade board. If I'm understanding the gist of it correctly this effectively upgrades the Mega ST2 to have, obviously, a twice as fast CPU and the RAM is effectively used as a really huge CPU memory cache, which is a considerably impressive feat for a computer of this era. We think of a 2MB cache on a modern CPU as being a marvelous accomplishment, but this was... twenty-three or more years ago!? Crazy! I also watched a episode of The Computer Chronicles, back when they were first adding the series to Archive.org, where they showed of the Atari "Transputer" , which allowed for slaving via a cable link of same model desktops to achieve parallel CPU processing, which was unquestionably waaaaaaaay ahead of it's time, pity that didn't really catch on back then.

 

Going to have to think hard on this as I have no keyboard. Guess decisions will be easier to make once I've attempted to POST the two computers. Will attempt posting them tomorrow and let y'all know how it goes, with pictures even if it goes well. Also will get the picture taken and up for the funny looking video box I got at the sale as well, it has a ribbon cable coming out of it that I am uncertain if it is some manner of secondary input or output, hopefully someone can help identify that mystery as well as neither of the two era catalogs I got from that same sale show anything like it... and am rather thinking it is something that was custom made.

Edited August 20, 2017 by game_player_s

[game_player_s]

Neither computer worked. Both turned on, and both output a virtually identical looking black screen with random red and green garble. Also have suffered the misfortune of having the memory card in my camera totally failing when attempting to pull the images from it this afternoon. Neither the camera nor my computer now recognize the card, so lost the pictures of the screen garble, and the video cable box thing. Will see about retaking the pictures of the video box tomorrow, but I'd already repacked away the TV used for testing. Lost my IR eclipse pictures too, grrrr.

Edited August 22, 2017 by game_player_s

[robdaemon]

That is an amazing find.

 

That accelerator looks awesome! I bet it's nearly impossible to find one of those for my Mega ST 2 I just got.

 

What's the empty PLCC socket for? I just got my Mega ST a few days ago, and I haven't cracked the case yet. Will be doing that in a few days when my Marpet XtraRAM 8 shows up

[game_player_s]

That is an amazing find.

 

That accelerator looks awesome! I bet it's nearly impossible to find one of those for my Mega ST 2 I just got.

 

What's the empty PLCC socket for? I just got my Mega ST a few days ago, and I haven't cracked the case yet. Will be doing that in a few days when my Marpet XtraRAM 8 shows up

Pretty sure it was for a Flux Capacitor add-on.

 

 

Here are the long awaited images of what I am now 100% positive is some manner of homemade video output box with a strange ribbon cable pass-through. Realized it was a typical old school Radio Shack type aluminum project box held together by friction so opened it up. Someone put some effort into making this is all I can say.

 

 

 

 

 

Edited August 23, 2017 by game_player_s

[mattsoft]

Have you tried connecting these up to a regular old RGB monitor? In other words, is the display problem with the homemade "video box" or with the Megas?

[game_player_s]

Have you tried connecting these up to a regular old RGB monitor? In other words, is the display problem with the homemade "video box" or with the Megas?

If I had to chance a guess, I'd say the video box is possibly at fault for the screen garble. But I have no other cabling to test them with, so who knows... oh idea.

 

Actually... I could put the Fluke on the video box to make sure there isn't signal crossover coming from one of the other input pins. Shall have to try that out late.

[mattsoft]

Or pick up an Atari RGB monitor or compatible 15Khz LCD monitor...do you know of any Atari enthusiasts in your area? Maybe a user group/computer club? it would be great to see those Megas working.

[robdaemon]

Pretty sure it was for a Flux Capacitor add-on.

 

Answering my own question, I'm pretty sure it's for the blitter. I just got my own Mega ST 2, and when I opened it today, I noticed it has the blitter and 4 mb of RAM, not 2 mb!

[game_player_s]

Good news! I found my Fluke meter this morning and made some rather fascinating discoveries about that Video output box.

 

First discovery, only have continuity from the computer port plug to the center pin of the RCA composite video output. No continuity to the outside of the RCA plug, this definitely explains the garbled video output from both computers.

 

Second discovery, opened up the box to verify if continuity was good on the video cable to the termination points, and it was. And this lead to the discovery of what the odd ribbon cable is likely for.

 

Found that not all of the wires from the Stereo A/V cabling meet up with with the input cable inside of the project box! Some are jumpered or wired to same termination points, but not all. I now firmly believe having examined this that the connector on the end of the ribbon cable was used for a security key. Without a termination key plugged into the blade socket, the audio and video wiring lines are incomplete, crazy! So all the original owner had to do to secure his computer from unwanted snooping when he wasn't around was pull out the security key and no one could hear or see output from the connected computer! This person went to a lot of trouble to have made something like this.

 

So what I now need is the wiring pin-out from the Mega ST2 Video Port so I can rig this up to work. (found)

 

Also have discovered another item I bought from the same sale is a accessory for the ST series computers, and not some sort of Apple computer attachment as first thought. Haven't taken pictures of it yet, but the device in question is a "Spectre GCR".

 

Which two pins should the wires for the RCA composite be connected to?

 

Edited August 27, 2017 by game_player_s