After posting this with in-line pictures, I have noticed that the pictures are not displayed, but are put in as "Posted Image" links that don't work for me, so I've updated this post with direct links to the pictures next to these disfunct ones. If you would like to see ALL the pictures I made of this, go to http://www.alphasys.nl/fotos/index.php?map=3&picture=DSC03264.JPG and click on the links under the word "Plaatjes", or download a ZIP file with all of them at http://www.alphasys.nl/downloads/PhotosAtariMonsterTower.zip (2.274.878 bytes).
Hello 8-bit fans!
It's been a while ago, that I'd asked if anyone would be interested to see photo's with an explanation of my "Atari in a big-tower". There were some. Now I actually have a decent enough camera and have the thing in the house anyways, instead of storage, it was about time to do it.
So here goes:
Front view, lots of switches, buttons and 7-segment displays.
Rear view, most connectors have a sticker next to them with their purpose, but I had more ports than stickers. Quite hard to read on this photo though. You can already see there's more going on than on a "standard" Atari XL/XE machine though.
So let's open this thing up... I hope you're sitting down...
Interior view when the cover is off. The crazyness starts to become apparent. That's a lot of wires.
In the back you can see the 130XE board (behind the "harddrive mount") and that ugly grey thing in front is the bottom plate of a 600XL. In the top-part, you'll recognise the 1050 Diskdrive with its own PCB below that. (Which was a delicate puzzle to get in there. I'm glad I could fit it in eventually.)
The 600XL is held in place only by the powerconnector and monitor plug, that have been tie-rapped to the "harddrive mount". I'll unplug those and let it drop out.
As you can see, it's not quite "original" anymore. The game-ports are replaced by wires, aswell as the keyboard "connector". These have all been externalised and made available on the backpanel, in the expansion area. (The big blue connector near the bottom of the case is for keyboard, with gameport A next to it. Gameport B is below that on it's own "strip".)
Observant hardwarians will also notice it has 64kB RAM instead of the standard 16kB, and I've done something to the PIA aswell. That rainbow of wires is hooked up to Port A and B of a piggybacked PIA, actually. This is part of the internal "Eightlink".
The housing of the 600XL still came in very handy though. It became my external keyboard. There's about 6 feet/2 meters of flatcable between the computer and keyboard now. Yes, that works fine, never had any weird behaviour with it.
Interior of the keyboard. I just hooked up the lines, in order, to a connector that's now part of the backplane of the 600XL housing. The cable is thus detachable.
This keyboard now works for BOTH computers. It was a bit of a puzzle, but I wired both computer-side connectors up in the same way. Now get me right, the 130XE does NOT have the same order of connections on the PCB side, but the keyboard matrix itself is (ofcourse) identical, so this was a viable solution. And I was glad too, since the keyboard of my 130XE had become so corroded that it would not work anymore.
If you're interested in it, I still have the "translation table" for these keyboards in my "little blue book of atari knowledge".
I guess I'll continue with the main machine part now, the 130XE board.
It's hard to show the thing properly, but I'll get to other parts in subsquent photos. As you can see, I also exported the keyboard (bundle of red wires) and gameports (2 bundles of black wires) to an external connector. I used connectors to plug into the gameports on the board this time, since that was easier when I had to take the board out.
You may also notice the pokey, with a small perfboard on top. Let me zoom in on that.
I know it's ugly, but yes, this is the stereo-expansion. The pokey on top is missing a lot of pins, because it was gutted from a broken Atari by someone with "sausagefingers" and then sent to me by mail in disfunct packaging. Even pin 37 was completely severed. After some careful filing, I managed to expose enough of it to solder a connection to that, but it would remain a weak spot, so I glued the perfboard on top to hold the stuff in place, while it also gave me a place to put the pull-up resistor. Luckily, the other severed pins are for the keyboard matrix and SIO stuff, which were not needed. Both the Pokey's have also been decoupled and linked to the 2 RCA outputs on the backside, so I can hook up stereo to a stereo directly, while the second pokey is also linked up to the amplifier that drives the monitor output, so I can still hear all 8 channels out of the TV if I would choose so.
Right behind the pokey's, you see an awful mess of black, red and multicolored wires. That is what actually prompted me to start this project. What you see there are actually 4 PIA's on top of eachother.
A view of the other side. PIA's with chip-sockets in between. Besides the "original" function, there's one for the internal "Eightlink", one for an external "Eightlink" and I can't remember what I was going to use the last one for. (It's been over 20 years...) Possibly a Stereo Covox thing, since I still had ideas about making a stereo x 8-bit sampler which would have been useless without proper playback device.
You can probably understand that this "pile" of PIA's would not fit in the original 130XE housing anymore. The case was also becoming quite ugly, since I had drilled so many holes in it for switches and LED's, which are now on the front panel. I already had replaced the foil of the keyboard with a PCB version, which I had made with the foil as a masking template, but even that one was starting to fail.
So, what else is there on the main board... Well, there's the memory expansion, for one thing.
This is one of the "of the shelf" expansion that's in here... A 256kB RAM expansion, which "replaces" the 64kB of the normal 130XE bankswitchable RAM. I didn't make this myself, just installed it myself. I did however make a slight change to it:
Hardwarians will know that the dynamic RAM inside the Atari is refreshed by something called "CAS-only refreshing". The actual reading/writing to it, requires another line called "RAS". I noticed that the expansion installation instructions required me to cut the line for the RAS signal, so the "normal" 64kB would not be read from or written to, but instead this line would now adress the 256kB expansion. That meant that this "original" 64kB would still be refreshed, but not accessible. What a shame!
What I did was actually very simple: I took this RAS line, and hooked it up to a switch, that would either connect it to the 256kB, or the "original" 64kB. That gave me a hot-switchable ram-expansion! By the flick of a switch, I could use an "Original 130XE" with 128kB total, or "turn on" the expansion and have 320kB adressable. (So, that's one of the 7 flipswitches explained.) Best thing is, that both these "ramdisks" are usable, will remain refreshed and can be switched between.
I used this a lot in conjunction with the Qmeg OS, where I would have my "bootable" 256kB ramdisk filled with my development programs, and when I wanted to test my program, I would save it to disk, switch the "ramdisk" to 64kB mode, reboot and test. Then after testing I would just switch back to the 256kB ramdisk, and reboot my development environment from there, with all its stuff still intact.
Now I mention Qmeg... Look here:
In this picture you see two chips. The one with the red sticker is the BASIC rom, which I also hooked up to a switch to be able to turn it off without holding "option". The other one has perfboard on it again. This is not your bogstandard OS ROM. It's actually a 256kB EPROM, where I used 160kB to stick in 10 OS versions. The perfboard on top is hooked up to the 4 "extra" adress lines on this chip, and connects it to one of the thumbwheels on the front panel. This neat little device has 10 "states" that you can select by pushing the +/- buttons on it, while it indicates its state by the number shown in the little viewport between those.
Besides the "standard" OS, I have the forementioned Qmeg OS in there, together with several "translator" type OS-es, and some special purpose OS-es. Most notable: Omnimon and Supermon for 800 compatibility, Omniview for 80 column textmode things.
I know, I could have fit 16 in there, but I already struggled to choose 10 and it fit the thumbwheel.
I already mentioned one "off the shelf" expansion. There is another one in the tower, but for understandable reasons, I can't make pictures of that... It's in the 1050 diskdrive, under the shielding. This little piece of splendor is called "Mini Speedy 1050 DS" and is Germany's answer to the well known "Happy" extension. It's fast, it's programmable and it sort-of has 2 "bootdisks" built in. Yep, another switch was needed. In the "up" position, booting the computer with the drive bay open, will boot up Bibo-Dos, which is Atari Dos 2/2.5 compatible, and can also handle Double Density disks. In the "down" position, this same manner of booting would load the High-Speed Sector copier.
There are 2 "downsides" with the diskdrive though, which I have solved with the 2 (black) push buttons on the front panel and the following nugget of electronics...
This ugly perfboard holds 2 monostable timers (the NE 555's) and a set of J/K flipflops. The timers are used to "debounce" the buttons, which would otherwise not be very reliable. Each button will toggle a J/K flipflop, while the circuit also makes sure that the features it will switch, are always in the "default" mode when it gets power.
The first button/feature is easy to understand... It's write protection. As soon as you turn on the stuff, the disk is safe, and there's no need for silly stickers that only get lost inside the drive over time. One push of the button, the LED above it turns red, and you can write to your disks, even when there's no notch on the side.
The other button handles a Speedy feature. It basicly "turns off" the high-speed transfer mode. Some games just don't like it when it's loaded faster than it expects, and that makes it fail. But still, those are few, so I've set the "default" to high-speed.
Now there's still more "perfboard" in this thing... Some of you may already have noticed something going on in the bottom.
Not a great picture, so I'll take it out and show it better.
Enigmatic? Well, this is a little driver board for the 7-segment displays and a selector. One display's the "currently adressed memorybank" of the Ramdisk in hexadecimal. The others were planned for other indicators, and you may notice the label "DWS 2 Romdisk" on one of the cables.
Now we get into painful territory, since this marks the state it's been in for 20 years... Stuff was planned here. Nice stuff. Fun stuff. But I doubt I'll ever make it happen... Because, well, the computer is dead.
Working with hardware is a lot of fun, but its also prone to mistakes. Not that I've ever broken anything with my soldering iron, or any of my expansions caused a cascade failure... It was the powersupply.
In one lapse of memory, while I was about to give my brother an opportunity to play Kennedy Approach among other games, I made a STUPID and UNFORGIVABLE mistake... I hooked up the 12V line to the computer, instead of the 5V one... The machine will never work again.
This Romdisk thing never came to be, although it was a sound idea, based on the way Qmeg "handles" the ramdisk to make it bootable, and the way this "RAS/CAS" selection works. The idea was to decouple the RAS line from all "extra" RAM and instead make the system adress a 256kB Eprom, filled with data from 2 bootdisks in single density in the manner that Qmeg reads it. The "DWS" refers to the second thumbwheel I have in the front panel. And yes, I was planning to add 10 of these 256kB Eproms, giving me a whole lot of programs I could have loaded "on the fly". Basically 20 SD disks worth of software.
Well, that's the end of this long, but hopefully interesting post. Maybe some of you got a few ideas from this.