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spinnaker15136

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Posts posted by spinnaker15136

  3. Posted

    I found the Atari Technical Reference manual to be invaluable for is kind of stuff.

    http://www.atarimania.com/documents/atari-800-technical-reference-notes.pdf

     

    The SIO stuff starts around page 40+

    It is that literal. I've hung a serial monitor on the lines and absolutely no surprises. IIRC, computer wakes up, sends a couple of STATUS commands down the line in the format listed in the manual, if a device is there, it responds to the STATUS command and they start talking. There's some other hand shaking that goes on like device only get 100 msecs to respond or the computer moves on, that is that groaning buzz you hear when you start up an Atari w/o anything attached.

     

    Happens to fast for human intervention in real time. By that I mean if you run something like SIO2PC or APE that monitor the communication things change in the display so fast you can't tell anything other then the last command. Just a wag, I found the TRM a fascinating read, couldn't put it down. I am a little weird that way. If you are kind of weird that way too or at least obsessive to the point where you will do anything to get the job done, the TRM is your best bet. Helps to speak a little 6502 assembly language too as there is a listing for the OS that lets you really get into the nuts and bolts.

     

     

    Looks like the hard copy I have from years gone by.

  5. Posted

    Was wondering if someone could point me to a SIO disk emulator project with source code comments in English?

     

    The piece I am mainly interested in right now is just the part that emulates the various Atari drives when it comes to the Atari talking to the disk dive.

     

    I think I found the source code for SDDRive max but I am having difficulty figuring ou the part of the code that emulates the disk drive communication and does the work of processing the various command from the host.

     

    https://github.com/kbr-net/sdrive-max p

     

     

    Can anyone help? The simpler the better as long as it is working. ;)

     

     

    Later I would like the code to read and write ATR files but for now I would be happy with just emulating a disk drive.

     

     

  6. Posted

    I'm fairly sure static RAM with battery backup has been common going back to the mid 80s at least.

     

    Re HDD alternatives - random access devices haven't been competitive ever re pricing overall or per Megabyte until the modern day with cheaper flash drives (maybe except for optical drives but they suffer re speed and reliability).

     

     

    I don't think it used battery backup. Pretty certain it was bubble memory as mentioned above.

  7. Posted

    Looking at service manual tech-tips, and the And the FAQ there's some other hints to issues of the pre-grass valley upgrades, there's quite a few changes:

    https://mcurrent.name/atari-8-bit/faq.txt

    http://atariage.com/forums/topic/254378-complete-list-of-techtips-change-orders-mods-etc/?p=3543286

    • The WD1771 controller chip had inadequate internal data separation, which is where the daughterboard came in to address that. Improves the drive's ability to distinguish between data pulses and clock pulses on the disk, lowering the chance of a misread.
      • The Western Digital WD1771 disk controller does in fact include a FM (single-density) data separator on-chip. Being an early integrated circuit design, the data separator is not particularly high-performance. This is referenced in the WD1771 datasheet, page 17: "NOTE: Internal data separation may work for some applications. However, for applications requiring high data recover reliability, WDC recommends external data separation be used." Source: http://www.glitchwrks.com/2014/01/30/cromemco-4fdc
    • The stepper motor circuit voltage was upgraded to a regulated 12V DC.
    • The increased power requirements from 20W to 30W meant the power adapter was upgraded to the 31VA 9VAC supplies, according to the FAQ analog 810's originally came with a 15.3VA supply! (C014319)
    • The redesigned power board contains a redesigned power supply, a tachometer/speed Switch I.C. (frequency to voltage converter) added to the tach circuit to stabilize the motor speed.
    • The separate analog board major changes are to the Read/Write circuitry: Operational amplifiers ("op-amps") and discrete transistors in place of transistor arrays, and a multiplexer chip for switching the Read/Write amplifiers.

    I've never had my hands on one of those early drives, but the early history is sure interesting...

     

    I am beginning to think this would be a huge undertaking for such a project.

     

    I have someone sending me a couple of PC drives. I am thinking the best thing to do is try to build an interface for them and fit it to an 810 case. I could probably leverage the work done like the folks that did SD Drive Max for the SIO part.

  9. Posted

    SSD was a pretty broad term before the modern day flash types came along.

     

    There was bubble memory which was promising for a while and nonvolatile but didn't go really far.

     

    I worked on mainframes and "solid state drives" were common - typically they were boxes with multiples of 32 Meg of RAM which were high speed and configured to look like normal volumes (although somewhat smaller, the typical smallest volume in the mid 80s was about 800 Meg). Fairly sure they could also have battery backup.

    A common use was for paging since main memory sizes were usually 32-512 Meg and paging to mechanical drives was pretty slow.

    Yes. That is it. He said it was bubble memory. I was thinking in today's terms. ;)

     

    Yeah I used to work on a PDP 11/02 system that loaded its program and database all from cassette tape. It would take at least a half hour to load. What should happen was it booted up into its operator terminal software. Often you would get the deadly @ symbol which meant you had to load all over again. But I had one system that had magnetic core. If there was a power failure and the battery backup failed (which happened often too) all I needed to do was restrat the software by jumping to an address.

    • Like 1

  10. Posted

    Was wondering if someone by chance might know this person I meet back in the day. I guess it was the early to mid 80s. Atari was pretty much in the mainstream for only a couple of years. Anyhow I met someone in Pittsburgh that designed and built a solid state disk drive for someone confined to a wheelchair.

     

    Can't remember how I met this person. I did work for a computer store around then and I think we may have sold Atari for a very brief period. Don't remember if I met him there or perhaps it was at another store maybe even previous to when I started working there.

     

    You have to admit that it must of been a heck of a feat to design something like that long before the internet.

     

    Just throwing it out there in case someone happens to remember such a device being built.

     

     

     

  13. Posted

    I have the original Atari 810. The one with the problem rear board. Other than the Grass Valley upgrade, was anyone tried to do a redesign?

     

    I might try and give it at least a look anyway. But first I would like to understand the over all issues with the rear board. From what I understand it was the RPM circuit that was unreliable. Was this pretty much the main issue?

     

    I am thinking it might be possible to redesign the rpm control section only. Patching in control lines from the side board might be challenging.

    • Like 1

  14. Posted

    Ugh, don’t do that. If you’re going to replace a resistor, do it right: remove the old one, clean out the through holes with a solder sucker or wick, then solder the new one in place.

     

    Well that is what I would do for anything I designed and built. Or even something I was repairing that was not working. But what I have is a working system and wanted the least invasive way to swap it out. ;)

  15. Posted

    Looks like he’s got an Incognito board in there - don’t ask; they’re not currently being manufactured. :)

     

     

    And from my search it looks like Incognito was to make the Atari 800 compatible with other Atari's?

     

    Man I missed out on a lot or have forgotten a lot. ;)

     

    Is that the Qmemiry board? Photo is awfully fuzzy. Ar there other boards in there too? Looks like multiple boards in the same slot?

  17. Posted · Edited by spinnaker15136

    Wonderful.

     

    attachicon.gif0428190748.jpg

     

    This is the color pot for the 800..

     

     

    Thanks! Well the blue is bluer but still have some of that magenta color in the characters.

     

     

    I'll have to get a color bar generator but need to get my SD-Drive Max up and running first. I still might need to resort to the mod posted above.

     

    Any idea what the coil adjustment on the bottom was for? I wonder if it was for the RF?

  18. Posted

    Ah I see it. I popped the hood. There is a hole drilled into the shield right about where I see the hole in the label. It is a coil with an iron core. When I look closer at the bottom I can see a hex iron core. Unfortunately my adjustment tool does not the right size. I am pretty sure I had a whole set of those back in the day.

     

    Guess I will need to look at the schematic unless someone can tell me what that coil is.

  19. Posted

    If you plan to use the machine with LCD or other modern displays, just go ahead and adjust the color potentiometer inside the 800 and see if you can get close to the correct “NTSC Atari blue.” (*) I take it you probably don’t have access to a SALT or SuperSALT test cart or a color bar generator program. If you do, you can load up the color bar test and adjust to match. If you don’t you can do it the old-fashioned way: load up a game that has pretty well-defined color on-screen at once and and adjust the colors to match. I like to use DIG DUG, JOUST or something like PITFALL. DIG DUG puts a lot of colors on-screen at once; JOUST lets you adjust by looking at the tendency towards green and red/brown; PITFALL lets you adjust to match the rich green of the jungle.

     

    The 800 color potentiometer is not accessible without taking the system apart, if I recall correctly. It’s mounted on the vertically-installed “personality board” at the rear of the main board, along with the 6502, ANTIC and GTIA. It’s been awhile since I’ve had one of my 800’s apart though so perhaps there’s an access hole there I don’t recall.

     

    (*) I say that because PAL systems have a bit of an aqua tint compared to the deeper blue of NTSC

     

     

    There is something on the bottom label. Right under the Atari logo. I have the hole broken out for some reason. Don't think it is a mounting hole. I tried to adjust. Either it is not turning, or it is simply having no affect or my screw driver is .not long enough. I also have one of those non metallic adjustment tools used for the old IF cans in radio and TV. But again not long enough.

  20. Posted

     

    Given how much electronics stuff I keep finding to work on and fix around here, a couple weeks ago I finally bought an actual oscilloscope - a Siglent 1202X-E. Amazingly powerful tool but definitely not “required” for most vintage fixes and repairs.

     

    I now have the same model. I started with an old analog Tek. Sold it shortly after I repaired it and got a look at that power supply. I feared having to repair it. ;) I then bough a Rigol. Owned it for a few years till it was time for a new toy when I bough the Siglent.

  21. Posted · Edited by spinnaker15136

    You have to completely disassemble everything to get to R189. But it’s worth it.

     

     

     

    Sent from my iPhone using Tapatalk

     

    So where is it. located? That is what I want to know. ;) And can you clip out the old one without lifting the board? I.E. solder the new one to the old leads.

  22. Posted · Edited by spinnaker15136

    Really I think most anything will do. There are lots of meters in the US $30 range that are more than adequate. I have a Mastech auto raging one. My only complaint is it shuts the LCD backlight off too quickly. Other than thar it served me fine.

     

    Save your money for a scope. I haven't used a logic probe in years. Just use the scope. I think I ended up selling my logic probe.

    • Like 1

  24. Posted

    I'd bet its the LCD but to be fair the RF and COMP picture directly out of the 800 are not stunningly good, especially compared to today's stuff. The tint sounds like the LCD as said..I have an old LCD TV and it does something similar and more so if you are not square on to the picture..

     

     

    Yes. Noticed exactly that. If you look at it straight on, it appears to be a bit better.

  25. Posted

    There's a very simple video mod for the 800 that involves replacing only 1 resistor:

     

    http://atariage.com/forums/topic/198862-atari-800-video-upgrade/?do=findComment&comment=2602329

     

    Appears it's only an improvement to S-Video Luma, or not composite.

     

    No s-vdeo in on my TV, What is the recommended way to convert s-video today? Get one of those HDMI adapters? Or is there something actually for the Atari out there?

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