UNIXcoffee928 Posted October 27, 2008 Share Posted October 27, 2008 I've seen questions about the hidden expansion ports on the 400/800 machines, however I've never seen any real answers. Both machines have aft card edge connectors, but you wouldn't know it, unless you've disassembled one, since there is no removable plastic hatch plate. Apparently, these connectors were used for quality control testing, after the components were assembled, and before the cases were put on in the factory, to make sure that the machines were working correctly. The leads are labeled as 'Test Points' in the manual, but they are not just simple test patches, they actually comprise a fully usable card-edge connector that contains the signals found on all of the expansion buses of all later Atari products. Of course, the schematics exist in .pdf format, in the hardware guide, but even if the scans were excellent you would not be able to read the test point signal identifiers, due to the extremely small print used, and the original reproduction technology, which is sometimes blotchy. Well, I just so happen to have an original printing of the hardware manual. The signals are almost readable there... so, I resorted to a magnifying glass (the lowest tech thing I've done all year, mind you). Now, Let me tell you, this was an ENORMOUS PITA. In some cases the print was just too blotchy to decipher, but, I was able to document both interfaces. That's right, BOTH... the 400 has a completely different expansion pinout than the 800. Now the world may know. ha. That's the good news. The bad news is that there was a lot of "is this blotch a 5 or a 3? is this blotch a 0 or an 8?"... so take the correlation of signal to pin VERY lightly & don't believe everything that you read... ha. ...but, at least you can get a good idea of what signals are present. Perhaps if enough people with printed hardware manuals cross-check it with their printing, maybe one day we'll have a definitive pinout. The other thing is that, like other card-edges, Atari chose to label pins alpha-numerically. UgggG. There is no real easy way to figure out which pin is which, for many, either, since they are not at all linearly mapped. Perhaps someone with adequate testing gear will have enough to go on, to match the signals to the pins, though, now that they know what they're looking for. Oh, yeah, there's going to be stuff in there where you'll need to do your own sanity checking, I just typed out what I saw. ALL of the signals are there, though, I didn't skip anything. & yes it gave me an huge headache. In any case, without further delay, here's what you've all been waiting for, the Legendary & Fabled, 400/800 Expansion Bus (Sorta...) ha. =========================== ============================== | 400 EDGE CONNECTOR | | 800 EDGE CONNECTOR | | TEST POINTS: | | TEST POINTS | =========================== ============================== | | PIN | FUNCTION | | PIN | FUNCTION | =========================== ============================== | AA | IRQ | | 24 | IRQ | --------------------------- ------------------------------ | 24 | A15 | | EXSEL | A14 | --------------------------- ------------------------------ | CC | A14 | | EXSEL | A13 | --------------------------- ------------------------------ | BB? | SYNC | | 28 | SYNC N/C | --------------------------- ------------------------------ | C | OSC CLOCK | | 3 | OSC CLOCK | --------------------------- ------------------------------ | 23 | NMI | | | | --------------------------- ------------------------------ | 25 | RESET M | | 22 | RESET M | --------------------------- ------------------------------ | 20 | A13 | | Y | A13 | --------------------------- ------------------------------ | 18? | A12 | | W | A12 | --------------------------- ------------------------------ | 7? | A4 | | U | A4 | --------------------------- ------------------------------ | 16 | A5 | | 17 | A5 | --------------------------- ------------------------------ | U | A11 | | V | A11 | --------------------------- ------------------------------ | V | A3 | | 18 | A3 | --------------------------- ------------------------------ | N | A2 | | 12 | A2 | --------------------------- ------------------------------ | 14 | A1 | | 3 | A1 | --------------------------- ------------------------------ | 12 | A0 | | 1 | A0 | --------------------------- ------------------------------ | W | A10 | | 21 | A10 | --------------------------- ------------------------------ | P | A9 | | 13 | A9 | --------------------------- ------------------------------ | 19? or 12? | A6 | | X | A6 | --------------------------- ------------------------------ | 13 | A7 | | ? | A7 | --------------------------- ------------------------------ | 18 | A8 | | T | A8 | --------------------------- ------------------------------ | D | REF | | | | --------------------------- ------------------------------ | S? | D7 | | K | D7 | --------------------------- ------------------------------ | J | D6 | | B? | D6 | --------------------------- ------------------------------ | M? or H? | D5 | | 7 | D5 | --------------------------- ------------------------------ | F | D4 | | 6 | D4 | --------------------------- ------------------------------ | 7 | D3 | | J | D3 | --------------------------- ------------------------------ | ? | D2 | | W? or M? | D2 | --------------------------- ------------------------------ | ? | D1 | | 3 | D1 | --------------------------- ------------------------------ | ? | D0 | | | | --------------------------- ------------------------------ | 22 | ?1 | | Z | R/W EARLY | --------------------------- ------------------------------ | 21 | ?2 | | 23 | 02 | --------------------------- ------------------------------ | 28 | Vcc | | | | --------------------------- ------------------------------ | 27 | CTIA CS? | | | | --------------------------- ------------------------------ | 1 | LUM 0 | | A | LUM0 | --------------------------- ------------------------------ | 11 | LUM 3 | | | | --------------------------- ------------------------------ | 3 | LUM 1 | | C | LUM1 | --------------------------- ------------------------------ | 2 | LUM 2 | | B | LUM2 | --------------------------- ------------------------------ | B? or 8? | VIDEO SYNC | | 2 | VIDEO SYNC | --------------------------- ------------------------------ | 4 | COL | | D | COL | --------------------------- ------------------------------ | EE | VDD | | 25 | VDD | --------------------------- ------------------------------ | 26 | VCC | | 27 | VCC | --------------------------- ------------------------------ | FF | VSS | | FF & 28? 26? | VSS | =========================== ============================== The following were VERY garbled: ============================== | F | D8 | ------------------------------ | AA | ?1 | ------------------------------ | 1 | ??SELECT | ------------------------------ | ?? | N/C | ------------------------------ | EXSEL | ?? 33? | ============================== Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 28, 2008 Share Posted October 28, 2008 Apparently, these connectors were used for quality control testing, after the components were assembled, and before the cases were put on in the factory, to make sure that the machines were working correctly. Yes, that was part of the PITS test. Atari was very advanced in their QC on the 400/800 machines. Quote Link to comment Share on other sites More sharing options...
Rybags Posted October 28, 2008 Share Posted October 28, 2008 (edited) I think the problem with using it as a poor-man's expansion connector is that: - what about address decoding? - What about any expansion device knowing whether or not a cartridge is present? - does the connector have any means of overriding what would normally be a resident RAM/ROM access (maybe EXSEL does that?) - existing expansions for the 400/800 seem to do their job just fine. - opens up possibility of yet more "defacto standards" to confuse the A8 world even more than it is now. Interesting though that it seems to have direct access to the Color/Lum and Sync lines from GTIA. Maybe opens up the possibility for a better video circuit (although the default one isn't in itself too bad). The possibility also exists, that since it was intended for production line test/QA, that it was engineered such that it only works with an external CPU in charge of the system, and that the onboard 6502 is somehow ignored or disabled. Edited October 28, 2008 by Rybags Quote Link to comment Share on other sites More sharing options...
UNIXcoffee928 Posted October 28, 2008 Author Share Posted October 28, 2008 This little exercise was just to satisfy curiosity, mostly, and to inform the community of the lineage of the various expansion buses. Of course, if people want to go hacking, more power to them! There is a document, by Bob Woolley, on adding a Parallel Bus Interface to the 1200XL. Since the 1200XL was the next system after the 400/800s, I would imagine that someone could zen out the path to a PIB on the 400/800s from that document. If you choose to do this, PLEASE, PLEASE run a ribbon cable out the back of your 400 or 800, don't destroy their cases. I'll have to look into the documentation for the various expansion ports, to get a clearer idea, via comparison of signal labels.... but, judging from the schematics, the signal lines run straight out of the cpu in a lot of lines, so, I would bet that it does function as a useful connector, without additional test equipment probing it. Can someone post a link to a good document covering the meanings & uses of the standard PIB signals. There are a lot of pinout pages, but, not a lot of pages that seem to define things other than by superficial references. Thanks! Quote Link to comment Share on other sites More sharing options...
+warerat Posted October 28, 2008 Share Posted October 28, 2008 This little exercise was just to satisfy curiosity, mostly, and to inform the community of the lineage of the various expansion buses. Of course, if people want to go hacking, more power to them! There is a document, by Bob Woolley, on adding a Parallel Bus Interface to the 1200XL. Since the 1200XL was the next system after the 400/800s, I would imagine that someone could zen out the path to a PIB on the 400/800s from that document. If you choose to do this, PLEASE, PLEASE run a ribbon cable out the back of your 400 or 800, don't destroy their cases. I'll have to look into the documentation for the various expansion ports, to get a clearer idea, via comparison of signal labels.... but, judging from the schematics, the signal lines run straight out of the cpu in a lot of lines, so, I would bet that it does function as a useful connector, without additional test equipment probing it. Can someone post a link to a good document covering the meanings & uses of the standard PIB signals. There are a lot of pinout pages, but, not a lot of pages that seem to define things other than by superficial references. Thanks! This card-edge is completely behind the metal shield when in its assembled state. Not to mention not enough clearance to plug a connector into it with it all put together. Most every signal you need for a XL-style PBI is there, with the exception of a minimum of two signals. And I've already done a PBI implementation for the 800 (I generate signals the missing signals available on the XE ECI connector) and connect a MIO via a pass-thru card that goes into a memory slot. Quote Link to comment Share on other sites More sharing options...
UNIXcoffee928 Posted October 28, 2008 Author Share Posted October 28, 2008 That's cool. Been a while since I had one open, yeah you're right, the shielding would be in the way. Can you post your pinouts for the 800 card edge? I've been trying to read them off of a very blotchy schematic. In any case, while you were writing that, I was building a text file that shows a comparison of the signals to the expansion port of the 5200. Since the 5200 is a closer relative to the 400/800 than the XLs are. Maybe you could fill in the blanks to help unravel the mystery. See attached file. Thanks. 5200_800_Signals.txt Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 28, 2008 Share Posted October 28, 2008 There is a document, by Bob Woolley, on adding a Parallel Bus Interface to the 1200XL. Since the 1200XL was the next system after the 400/800s, I would imagine that someone could zen out the path to a PIB on the 400/800s from that document. Except the 1200XL can easily take an XL ROM with PBI support built-in, the 800 cannot. If you choose to do this, PLEASE, PLEASE run a ribbon cable out the back of your 400 or 800, don't destroy their cases. You'll have to mill a hole in the shield to get it out. right at the seam. This is an 800, remember. The 800D development units have a massive hole in the left side of the shield to get the ribbon cable to the left-hand I/O board. Quote Link to comment Share on other sites More sharing options...
UNIXcoffee928 Posted October 28, 2008 Author Share Posted October 28, 2008 This is the first that I've heard about the 800D. This page has a little info on it: http://www.atarimuseum.com/computers/8BITS...I800/800-d.html Do you have any more info or pictures? This is also the first that I've heard about Atari's major involvement with Cromemco. Since this is the case, I would say that there is a strong possibility that some Cromemco/S-100 Bus technology influenced the Atari 8-Bit architecture design philosophy. Does anyone know which Cromemco models were used at Atari? There is a nice collection of Cromemco manuals here: http://www.hartetechnologies.com/manuals/Cromemco/ Design of the 5200 began in 1980, and it was released in November of 1982. The 1200XL was released before mid 1983. Both technologies were probably being designed simultaneously by two separate teams. The expansion bus on the 5200 seems to be very close, indeed, to the Test Point Card Edge Connector on the 800. Can someone provide a one sentence description of the function for the following 5200 pinouts: 04. R/W Early 05. Enable E0-EF 16. Audio In 18. System Clock 01 Like, why would Audio go in? Also, if someone could explain the explicit function of each of the Address Lines, numerically, that would be helpful. For instance, why aren't all of the address lines used, and why the jump from A11 to A14. I'm sure that this has something to do with the 5200 being limited to 16K, but what are the functions of each line? Also, are the Data Lines Big Endian or Little? Please bear with some of these questions, I'm not an electronics professional, and I have a lot to learn. Here is the full numerically sorted pinout for reference: 01. +5V DC 02. Audio Out (2 port 5200 only, not connected on original) 03. Ground 04. R/W Early 05. Enable E0-EF 06. D6 Data Line 06 07. D4 Data Line 04 08. D2 Data Line 02 09. D0 Data Line 00 10. IRQ 11. Ground 12. Serial Data In 13. Serial In Clock 14. Serial Out Clock 15. Serial Data Out 16. Audio In 17. A14 Address Line 14 18. System Clock 01 19. A11 Address Line 11 20. A7 Address Line 07 21. A6 Address Line 06 22. A5 Address Line 05 23. A4 Address Line 04 24. A3 Address Line 03 25. A2 Address Line 02 26. A1 Address Line 01 27. A0 Address Line 00 28. Ground 29. D1 Data Line 01 30. D3 Data Line 03 31. D5 Data Line 05 32. D7 Data Line 07 33. Not connected 34. Ground 35. Not connected 36. +5V DC Thanks! Quote Link to comment Share on other sites More sharing options...
ClausB Posted October 28, 2008 Share Posted October 28, 2008 (edited) Can someone provide a one sentence description of the function for the following 5200 pinouts: 04. R/W Early 05. Enable E0-EF 16. Audio In 18. System Clock 01 Like, why would Audio go in? Also, if someone could explain the explicit function of each of the Address Lines, numerically, that would be helpful. For instance, why aren't all of the address lines used, and why the jump from A11 to A14. I'm sure that this has something to do with the 5200 being limited to 16K, but what are the functions of each line? Also, are the Data Lines Big Endian or Little? 04 is the "Read / not Write" signal from the CPU, undelayed (as opposed to "R/-W Late", delayed for DRAM timing, IIRC). 05 is from the address decoder, signalling that the CPU is accessing an address in the range $E000 to $EFFF. 16 is for the 2600 expansion unit's sound output, which goes through the 5200's audio circuit to the TV. There's also a video input for the 2600 expansion unit. 18 is the CPU's 1.79 MHz clock phase 1. A11, combined with Enable E0-EF, decodes the address range $E000 to $E7FF, a block unused on the motherboard. A0 through A7 are the low 8 bits of the address bus, used to address within the $E000 to $E7FF block decoded above. You've got 256 bytes of space to add peripheral I/O or banked RAM or ROM. Why A14 is there is a complete mystery to me! Data line D7 is the high bit and D0 is the low bit. See also my article at http://www.videogames.org/html/5200Stuff/5200.notes.html and my posts in the 5200 threads. Edited October 28, 2008 by ClausB Quote Link to comment Share on other sites More sharing options...
Rybags Posted October 28, 2008 Share Posted October 28, 2008 Maybe you could fill in the blanks to help unravel the mystery. See attached file. Thanks. Looking at your file, and the table in your original post... (I've got an original Hardware Manual in pretty good condition) CS = Chip Select. Reset M would more likely be "Reset Machine", ie the Reset line going to 6502 and most other custom ICs. "System Reset" is merely an NMI. CTIA CS = most likely Composite Sync. The D0 line is present at connection "F" on the 800 test point. Lots of the printing is hard to read due to size and the font they've used. Since most things are labelled more than once, you can trace the circuit and sometimes find an easier to read label. Also, tracing the lines back in some cases gives way what the function of the line is. Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 28, 2008 Share Posted October 28, 2008 This is the first that I've heard about the 800D. Do you have any more info or pictures? I've got the same unit as Curt. I need to reshoot my whole Atari collection some day, my photo-tour is eight years old, and I did not have the 800D at the time. This is also the first that I've heard about Atari's major involvement with Cromemco. Since this is the case, I would say that there is a strong possibility that some Cromemco/S-100 Bus technology influenced the Atari 8-Bit architecture design philosophy. Does anyone know which Cromemco models were used at Atari? I doubt it was anything significant. The S100 bus was very very popular for many years, in particular among the hobbiest crowd, but there were many similar computers (the KIM-1 for example) and it's a basic bus design. I don't see it any more S100 influenced than anyone else, really. Once Atari was not able to do a real bus with real expansion cards due to the FCC (and the TV shielding I explained in another thread), it was just down to a memory bus with slots, basically. 04. R/W Early 05. Enable E0-EF 16. Audio In 18. System Clock 01 Like, why would Audio go in? On the 800, "AUDIO IN" was used for the voice track of the tape drive. I would have expected it was for expansion, such as adding a (decent) 2600 emulator, storage device or modem. Also, if someone could explain the explicit function of each of the Address Lines, numerically, that would be helpful. For instance, why aren't all of the address lines used, and why the jump from A11 to A14. I'm sure that this has something to do with the 5200 being limited to 16K, but what are the functions of each line? I'd have to check the Atari memory map, but I suspect you'll find your answer in how the memory-mapped I/O is handled. I don't have any Atari manuals with me at the moment. Also, are the Data Lines Big Endian or Little? Not sure what you mean here. Data lines are just binary, there is no "endian". D0 is the lowest bit and D7 is the highest. The concept of "endian" only appears at a higher level, when you're dealing with shipping multiple bytes of data. You can only ship one byte at a time over the data lines. The 6502 is little-endian, though again it does not matter at this level. Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 28, 2008 Share Posted October 28, 2008 This is the first that I've heard about the 800D. Do you have any more info or pictures? I've got the same unit as Curt. I need to reshoot my whole Atari collection some day, my photo-tour is eight years old, and I did not have the 800D at the time. This is also the first that I've heard about Atari's major involvement with Cromemco. Since this is the case, I would say that there is a strong possibility that some Cromemco/S-100 Bus technology influenced the Atari 8-Bit architecture design philosophy. Does anyone know which Cromemco models were used at Atari? I doubt it was anything significant. The S100 bus was very very popular for many years, in particular among the hobbiest crowd, but there were many similar computers (the KIM-1 for example) and it's a basic bus design. I don't see it any more S100 influenced than anyone else, really. Once Atari was not able to do a real bus with real expansion cards due to the FCC (and the TV shielding I explained in another thread), it was just down to a memory bus with slots, basically. 04. R/W Early 05. Enable E0-EF 16. Audio In 18. System Clock 01 Like, why would Audio go in? On the 800, "AUDIO IN" was used for the voice track of the tape drive. I would have expected it was for expansion, such as adding a (decent) 2600 emulator, storage device or modem (the 1030 used the audio-in to transfer the telephone sound to the Atari and the TV speaker during dialing and connect). You've already got support for it in the machine's chipset, might as well set it up for later use. Also, if someone could explain the explicit function of each of the Address Lines, numerically, that would be helpful. For instance, why aren't all of the address lines used, and why the jump from A11 to A14. I'm sure that this has something to do with the 5200 being limited to 16K, but what are the functions of each line? I'd have to check the Atari memory map, but I suspect you'll find your answer in how the memory-mapped I/O is handled. I don't have any Atari manuals with me at the moment. The function of the address lines? They specify the address you want to access in binary. So if you want to access something at memory location 32767, you would have 0011111111111111. 32768 would be 0100000000000000. Also, are the Data Lines Big Endian or Little? Not sure what you mean here. Data lines are just binary, there is no "endian". D0 is the lowest bit and D7 is the highest. The concept of "endian" only appears at a higher level, when you're dealing with shipping multiple bytes of data. You can only ship one byte at a time over the data lines. The 6502 is little-endian, though again it does not matter at this level. Quote Link to comment Share on other sites More sharing options...
Curt Vendel Posted October 28, 2008 Share Posted October 28, 2008 (edited) The 800D is just a standard 800 that consists of a replaced CPU card by a company called STC, it is the same assembly as the original Atari CPU board, just having its components rearranged to accomodate a 40 pin header for the ribbon cable that goes to the right side board that is unique to the 800D. The Right side board has 2 Serial ports with manual select switches to set their baud rate connected to a pair of 6850 rs232 chips. There are a pair of eprom's for the board, a Mostek 4118 (1024x8 SRAM) and a Signetics N82S115. The CPU board header is directly wired for the most part right to the 14806 which is the 6502. It is true, the "Test Edge" is really an extension out of the 400/800... I personally think it is a shame that Atari didn't just put a plastic punch out panel on the back of at least the 800 case with a screw off aluminum RF plate behind it. This would've allowed for an assembled access to the board for testing at Atari, but it might've opened the door for 3rd parties (or perhaps even Atari itself) to have come out with an Expansion box of some sort. Imagine a box that plugged into the back of the 800 that was as wide as the system case, had the same vent styling and was perhaps 12-14" back (enough of a footprint for a monitor or TV to rest ontop of it!) Now THAT could've made for the ultimate Atari 800 upgrade - having an expansion box. Now this would'nt have been PBI, this would've been an extension of the internal slots, but it may have opened up the opportunity for more 80 column or rgb graphics cards... a company run on the side by an Atari HCD employee called CMC sold a Parallel/Serial card that plugged into slot 3 of the 800, so other peripherals (video cards, modems, printer cards, etc...) could've been made for this expansion box. Interfacing from an 8bit bus to an 8bit Xebec SASI to MFM controller board would've been very feasible, so having a hard disk system connected to the Atari 800 bus would've been possible... Remember, if you could plug in nearly anything into an S-100 bus computer, there is no reason - with a little design work, that such things could've been designed for an Atari 800, its bus was robust enough and had more then enough of the proper signals and interrupts to have handled 3-4 devices. So it would've been a realistic possibility. Curt Edited October 28, 2008 by Curt Vendel 1 Quote Link to comment Share on other sites More sharing options...
Curt Vendel Posted October 28, 2008 Share Posted October 28, 2008 Image of CPU board and Right Panel Board of 800D. Curt 1 Quote Link to comment Share on other sites More sharing options...
ClausB Posted October 29, 2008 Share Posted October 29, 2008 Image of CPU board and Right Panel Board of 800D. Thanks for the interesting look at an 800D. Is this hardware at all related to the "LINBUG" debugger mentioned in the published Atari OS listing? Quote Link to comment Share on other sites More sharing options...
UNIXcoffee928 Posted October 29, 2008 Author Share Posted October 29, 2008 That's really cool. Too bad they didn't leave the two RS-232s on the system for production! I bet that that board evolved into the 850 Interface, does it have the same components? Thanks for the usage tip on Endian-ness. Yeah, my background is at a higher level, but I've always had an interest in lower-level stuff, and now I have the time to learn more about it in detail. I know quite a bit abut OS design & system architecture at a slightly higher level, however the nitty-gritty electronics at the most basic level is something that I'm finally getting around to studying full-time... took me long enough, right? = ) Been working backwards for what, like 29 years now... ha. Always something new to learn! Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 29, 2008 Share Posted October 29, 2008 Wow, I quoted my whole message instead of editing it. Boy that makes me look stupid, and I hardly need any help in that department. I don't generally have time for this-sort-of-thing, so I'm often either sick or in a hurry when I'm posting. Not always the best plan... Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 29, 2008 Share Posted October 29, 2008 (edited) It is true, the "Test Edge" is really an extension out of the 400/800... I personally think it is a shame that Atari didn't just put a plastic punch out panel on the back of at least the 800 case with a screw off aluminum RF plate behind it. This would've allowed for an assembled access to the board for testing at Atari, but it might've opened the door for 3rd parties (or perhaps even Atari itself) to have come out with an Expansion box of some sort. Would have been really cool. I imagine the reason they did not is the FCC. That not only killed the card slots, it caused all sorts of problems for many of the peripherals. FCC might have complained that a user could remove that cover and then the 800 would not meet the required shielding standards. And Atari knew they could not make an affordable cable that would plug into that slot and still meet shielding, so there's no reason to put it there. It would have driven up costs on what was already a rather expensive unit to produce... That factory-installed RF modulator gave Atari an edge, but it also cost them dearly in terms of design until the FCC changed the rules in '82. Smaller companies just ignored the rules, but Apple and Atari had to play by them. You either had RF output or flexible hardware. Not both. Curt, you may recall that we talked about this very thing like 14 years ago; I wanted to build an expansion unit that plugged into the 800 test connector. But when I entered graduate school, time was no longer my own... Imagine a box that plugged into the back of the 800 that was as wide as the system case, had the same vent styling and was perhaps 12-14" back (enough of a footprint for a monitor or TV to rest ontop of it!) Now THAT could've made for the ultimate Atari 800 upgrade - having an expansion box. Now this would'nt have been PBI, this would've been an extension of the internal slots, but it may have opened up the opportunity for more 80 column or rgb graphics cards... a company run on the side by an Atari HCD employee called CMC sold a Parallel/Serial card that plugged into slot 3 of the 800, so other peripherals (video cards, modems, printer cards, etc...) could've been made for this expansion box. Interfacing from an 8bit bus to an 8bit Xebec SASI to MFM controller board would've been very feasible, so having a hard disk system connected to the Atari 800 bus would've been possible... Would have been fantastic. The Bit-3 card is cool, but what a hassle to install, trying to get the cable out of the shielding box on the Atari. Remember, if you could plug in nearly anything into an S-100 bus computer, there is no reason - with a little design work, that such things could've been designed for an Atari 800, its bus was robust enough and had more then enough of the proper signals and interrupts to have handled 3-4 devices. So it would've been a realistic possibility. I would argue that all of the "problems" with the 800 bus are because they could not use it as a GP-expansion bus, so they did not bond all signals to all cards. Made addressing easy if you could build the limitaions into the slots, like PCI. Ironically, today I solved a problem I had with an Atari 800 a friend bought used in 1984, when the real 800s were hard to get. Always had occasional video noise, we never could figure it out. I was reading a "Compute" from 1982 today and saw an ad for a Mosaic card, bragging that it did not mess up your display. Then I realized that card had a no-name 32K upgrade card. I bet there were not enough filter capacitors on that card. I remember later that the problems from that machine seemed to move to another machine. The card got moved to that machine. I had never realized it until today. It's so obvious now, but at the time I was looking in the wrong places. Chris Edited October 29, 2008 by Chris Strong Quote Link to comment Share on other sites More sharing options...
Chris Strong Posted October 29, 2008 Share Posted October 29, 2008 (edited) That's really cool. Too bad they didn't leave the two RS-232s on the system for production! I bet that that board evolved into the 850 Interface, does it have the same components? No, they were totally different. The 850 interface is a lot more advanced. It's actually my very favorite Atari product. It is totally overdesigned for the needs of most users; I'm sure it was someone's pet project. It was really quite inexpensive when you consider all the things it did. I challenge people to find a card for a PC today with all the features of the 850. I suspect the 800D side board was developed by an outside contractor. Curt may have more information on this. Of course, he also has the IEEE488 interface, which I lust after since I spent four long years programming IEEE488 devices... architecture at a slightly higher level, however the nitty-gritty electronics at the most basic level is something that I'm finally getting around to studying full-time... took me long enough, right? Not uncommon for CS types! Just like EE's tend to know nothing about proper programming practice. It's hard to specialize in everything. -Chris Edited October 29, 2008 by Chris Strong Quote Link to comment Share on other sites More sharing options...
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