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Type: Posts; User: Petrofsky

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  1. TRS-80 Model 4 and the apocryphal Z80-socket-compatible 48-pin Z800 design

    I finally got around to really taking a look at the TRS-80 Model 4 Z800 support, and I was surprised to learn that the hypothetical Z800 that the Model 4 can accommodate was not only never produced,...
  2. The Model 100 line uses a cassette format with a...

    The Model 100 line uses a cassette format with a line encoding that is identical to the Model III/4 high-speed, 1500 baud, wave-based (i.e. zero-crossing-detector-based) encoding. However, the Model...
  3. Hadn't heard of this either, but some searching...

    Hadn't heard of this either, but some searching reveals XPLO has had an interesting extended life. See the website at xpl0.org. At some point its name changed to XPL0 (last character now a zero) and...
  4. It's likely that when you start BASIC, memory...

    It's likely that when you start BASIC, memory above 8000h is being accessed. See page 7-5 of the manual, about TOPMEM.

    After booting, use DEBUG to see what value is at 4049h. If it's higher than...
  5. What happens when you put memory in board B, and...

    What happens when you put memory in board B, and start up diskless and enter 32000 for memory size? Does your 16k ram in the keyboard then work okay? Iím wondering whether the EI is really causing...
  6. See page 7-12...

    See page 7-12 of the fine manual:
  7. Thanks for pointing out these interesting...

    Thanks for pointing out these interesting catalogs by an interesting company. Looks like they have a lot of useful info if you're living as a cheapskate in the nineties. Did you realize that that...
  8. Can you program the CRTC to get a 64-column mode?...

    Can you program the CRTC to get a 64-column mode? Once you do that, I'd think it would be quite feasible to port Galaxy Invasion and other Model I games.

    At least, it should make it...
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    The upper-case-only Model I can only store...

    The upper-case-only Model I can only store character codes 32 to 95. The hardware converts any other 7-bit codes into that range by flipping bit 6. So, 0-31 map to 64-95, and 96-127 become 32-63....
  10. Checking both the 2.2 and 3 manuals, I think it's...

    Checking both the 2.2 and 3 manuals, I think it's guaranteed that you will get either a 1 or 4, and you can easily distinguish true EOF by doing a COMPUTE FILE SIZE.

    So the full algorithm is:
    1....
  11. Doesn't the error code 1 return from the...

    Doesn't the error code 1 return from the high-level READ RANDOM call give you exactly that?



    Well, that doesn't sound any harder than what a sparse-preserving file copy program in Unix does. ...
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    That appears to be a Model 4 PAL board, either...

    That appears to be a Model 4 PAL board, either 8709296 REV B or 8709296 REV C (confirm by reading the part number printed on the board, near the Z-80). I'm curious what the outside of the system...
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    A photo of the whole board and of the outside of...

    A photo of the whole board and of the outside of the computer may also help. There are no PAL chips in a Model III. It sounds like this is actually a Model 4 board. Perhaps the system is an upgraded...
  14. But that would be strange too, because that's the...

    But that would be strange too, because that's the same trace that feeds A6 to the second bank of RAM. That is, neither A6 nor A13 run all the way to the RAM. The RAM just sees the post-mux signal...
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    You're unlikely to find any "TQD8446" chips. The...

    You're unlikely to find any "TQD8446" chips. The "8446" refers to a single production week (week 46 of 1984). The difference between "TQD" and "FQD" is trivial.

    Any chips with the Tandy part...
  16. Yes, sort of. Oops. That was the way. ...

    Yes, sort of.


    Oops. That was the way.



    All the ROM knows how to do is load and execute track 0, sector 1 of drive 0.

    You could burn your own ROM that scans the keyboard and then loads...
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    Well, you can write a routine that simulates the...

    Well, you can write a routine that simulates the Z-80's "OUT (C), A" instruction on a RAM-less system, but you'd have to use almost 800 bytes of ROM, which is kind of ridiculous. Here's a 781-byte...
  18. You also have a later keyboard with ALPS...

    You also have a later keyboard with ALPS keyswitches, so I would guess it's a 1979 system. I don't know much about the serial numbering. You can find lots of individual dates on the components inside...
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    As it turns out, if you both move the LD and...

    As it turns out, if you both move the LD and change DE to BC, you'll discover that a working and shortest-possible literal is 21748737887606944D15.

    What BASIC is doing as it reads each digit is...
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    That's a neat trick, but it's unfortunate that...

    That's a neat trick, but it's unfortunate that that "POKEI,42" is necessary. If Level II BASIC's number reader used the proper sort of rules that were eventually mandated for IEEE floating-point, you...
  21. Wow, what is that monster on the floor on our...

    Wow, what is that monster on the floor on our side of her desk in the second pic? Did Tandy ever sell a tower that big?
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    Iím confused. Are you talking about writing a...

    Iím confused. Are you talking about writing a program that runs on a TRS-80 and simulates a connection to Compuserve, without actually connecting to any remote service? If so, then what do arcade...
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    Your dump of your 8044316A looks identical to the...

    Your dump of your 8044316A looks identical to the MESS 8044316A dump to me (CRC 444c8b60). What difference are you seeing? What's the CRC of the 8044316A dump that you thought you got from MESS?
    ...
  24. Thread: Model 4 Font

    by Petrofsky
    Replies
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    I should mention that taos23 doesn't have the...

    I should mention that taos23 doesn't have the original two-crystal PAL board (labeled "8709296 REV A"). He has the later single-clock PAL board (REV B or C). Most of the changes are in the upper left...
  25. Thread: Model 4 Font

    by Petrofsky
    Replies
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    2,128

    Hey Larry, when I tried to respond to your...

    Hey Larry, when I tried to respond to your private message I got "ldkraemer has exceeded their stored private messages quota and cannot accept further messages until they clear some space."


    ...
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