Jump to content
Have You Played Atari Today?
2600|5200|7800|Lynx|Jaguar|Forums|Store  

jens-eike

Members
 View Profile  See their activity

  • Content Count

    92

  • Joined

  • Last visited

Posts posted by jens-eike

  1. Posted

    What I find a bit weird are the varying colors on the screen. So are there characters really shown as blue? Or is this just an issue of the screenshot?

     

    The lines in the Master Title Screen colorbars are not correct either.

    That is normal, if it is NTSC - ringing of the video signal at sharp edges (contrasts) gives all kinds of colorful effects :-(

  6. Posted

    The TMS991xx can add wait states to any operation (memory, internal, cru), so it should be possible to use the 9902. The 9901 can be replaced by '251 (input), '259 (output) and '348 (interrupt priority) TTL chips without speed penalty.

    Bonus: the TMS991xx can do parallel I/O for CRU addresses above >8000

  7. Posted

    Another note: check your timing requirements. 100ns RAM could be too slow for worst-case operation. Consult the data book, from address stable to data in is much shorter than 330ns!

    According to my TMS9995 Data Manual (December 1984), page 56, the access time is 3/4*tc2-135 (3/4*333-135=114ns with a 12MHz clock, at 16MHz: 3/4*250-135=52ns). Subtract any delay from TTL buffers or decoders like 74LS244 (30ns) or 74LS138 (39ns) and a '245 (40ns) buffering the data bus (maximum values from The TTL Data Book 1987). As you can see, LS-TTL logic is not going to make it, that's why TI invented the automatic first wait-state.

    Using faster logic (ALS/F/ACT...) and really fast RAM (628512 is available in 55ns) can do the trick.

    • Like 1

  9. Posted

    Actually, both CPUs run on 12MHz.

     

    The 9995 has an internal clock generator deriving it's microcycles from the crystal, externally, all we see is the memory cycle and the -phi clock output.

     

    The 9900 gets four clock phases from it's TIM9904(A), derived from a 12MHz crystal (older TIM9904 use a 48MHz crystal, most 99/4 have these). Peripheral chips like the TMS9902 use only one phase of the clock signal, so a 3MHz signal -phi3 controls most of the timing.

     

    Note: -phi3 is one fourth of the clock signals, so it's duty cycle is about 80ns active (low) and ~250ns inactive (high) (+/- rise and fall times). Early 9901s had a problem with the 50% duty cycle of the 9995, so TI produced chips marked TMS9901-95 and TMS9902-95 for compatibility with the 9995.

  10. Posted

    Before getting into trouble changing to a PC power supply and modifying all your cards (and remembering the mod everytime you test another card/your cards in another box), you should test the rectifier diodes on the PEB power board.

    When I got my first HDD, I upgraded the regulators to 2A types, but the diodes weren't up to the load. It took me 5 fuses to diagnose the problem. Now the box is working without problems since 1988.

  12. Posted

    Now we really need Thierry's site...

    The problem I could imagine is the console interrupt routine. When the 9901 timer issues an interrupt, the console checks for VDP and cassette interrupt, then DSR interrupts (where an error in the RS232 card prevents further service), and when nothing is found, your interrupt routine gets it's turn. This way, you will lose a lot of time...

  15. Posted

    50464 are 64k*4bit.

    Two of them are 64kByte, so your card is 512k with 16 chips.

     

    I need the manual for the Myarc 32/128k Memory Expansion card. I cannot find mine. I need to test it out. I want to know a) if it works, and 2) how much RAM it has. I opened it up and the RAM chips say the following:

     

    Japan 8648

    HM50464P-15

    U1005ZZ

     

    attachicon.gifmyarc ram chip.jpg

     

    Guessing these are 64K chips, so since there are 16 of them means this is a 128K card... right?

     

     

    Darryl

  16. Posted

    Some good reading about Karl Guttag's work with the TMS99xx family:

     

    http://spatula-city.org/~im14u2c/vdp-99xx/

     

    About the 8/16-bit bottleneck: In his notes, he mentions the 9985 originally planned as CPU for the 99/4. The 9985 was derived from the (flawed) 9940, it was an 8-bit CPU made to work on the 16-bit instruction set....:

    Quote: "The 99/4 was originally slated to use the 9985 CPU and not need the 9901 at all. The 9985 CPU was going to be a variation of the 9940 “microcomputer” with embedded EEPROM. The 9985 replaced the EEPROM with 256 Bytes of on-chip RAM. The 256 bytes of on-chip RAM was for the GPL and Basic interpretation, and had to be shared between instructions and data.

     

    The 9940 was a terrible design, it was big, slow and had a huge number of design bugs and to top it all off, there was huge pressure from management. So the 9985 was waiting behind getting the 9940 debugged and the 9940 was very hard to debug the way they designed it.

    [...]

    Now the 9900 had a 16-bit CPU with a 16-bit ALU and a 16-bit external interface but it was pretty inefficient and took 14 clock cycles to do a register to register add. The 9985 had only an 8-bit ALU and 8-bit I/O and took about 10 cycles to do a register to register add. Inside the 9985 the interface to the 256 bytes of RAM was also only 8-bits wide. To emulate the 9985, the 99/4 had to add hardware to covert the 16-bit bus coming out of the 9900 to act like the 8-bit bus of the 9900."

     

    source:

     

    http://spatula-city.org/~im14u2c/vdp-99xx/e1/99-4_History_By_KG_in_answers_to_Matthews_Questions.doc

    • Like 1

  17. Posted · Edited by jens-eike

    A "normal" TI DSDD disk (40 tracks) has 1440 sectors (=360k), so your example is missing half it's capacity. Try 18 sectors/track and your 80-track disk gets up to 2880 sectors.

     

    I'd like to be ready to rock & roll when this thing comes, with a minimum of screwing around, so I'd like to ask a favor of a helpful owner of an HxC.

     

    Could you post a picture of what settings you use to make a DSSD 80 track disk.

    (I don't think this is it):

     

    gallery_35324_1027_23417.jpg

     

    I know I could probably just convert a disk formatted with DM2K, but I'd like to know the actual specs.

     

    THANKS!

  19. Posted

    That is it!

    I found my disk, and in the source code it says "The Bill Gronos Sound Show"

     

    This is probably the program you are looking for. I think that I have it on disk and just have to find it. It appeared in the publication RD Computing from Ryte Data. I will post it when I find it or will recreate it from the listing.

    Jacques


    1:15:1. TI-99/4 secrets and curiosities
    by Bill Gronos
    Brush the cobwebs off your cassette port and
    see sound in sixteen colors
    This month I've got a program that is going to make your eyespop. It's the closest thing to an LSD trip that your 99/4 canproduce.
    If you read my previous article, you'll remember that I gave you three simple Assembly Languageprograms to take music input through the cassette port and display it graphically on the screen. TravisHolland in Austin, TX writes, "Widgeon has been playing his Spike Jones tapes with #1, and is ready fordifferent colors for different frequencies". I think Widgeon is going to be very pleased after he types in thismonth's two programs — unless he happens to be epileptic. If he is, you'd better have a stick handy, Travis,to put in his mouth when he runs the second program.
    The second program is so fantastic it makes me want to add my computer and video monitor to my soundsystem as a permanent fixture. If you were fortunate enough to start out with a disk drive (unlike myselfwho labored with a cassette recorder for what seemed like forever), you really need to come up with acassette cable just to see the amazing things your 99/4 can do with a sound input. If you don't have one,check in the computer bargain papers! I've seen TI cassette cables advertised for $1.50, which is probablyless than what the connectors alone would cost you. It's also easy to make your own. Then you can stickon whatever mating plug your music device requires. Just about any sound device can be used to providean audio input: tape recorder, radio, TV, Walkman, etc. If you wish to make your own cable, the audioinput pins on the cassette port connector are numbers 8 and 9. On the standard TI cassette cable, pin 8goes to the tip of a mini plug, and pin 9 goes to it's sleeve. This plug is inserted into the earphone orexternal speaker jack on the cassette recorder.

    • Like 1

  21. Posted

     

    V1? V2? the com1 or rs232/9902 model?

    Must be the 9902 based nanoPEB.

    from Stuart's source code:

     

    *Set port 1 to 1200 Baud, 7 data bits, no parity, 1 stop bit.

     

    LI R12,BA9902 CRU base address of 9902 in NanoPEB.

    SBO 31 Reset 9902. This sets /RTS inactive high, so the

    * RTS output line to -ve voltage.

  25. Posted

    Some RTC/SRAM chips access the clock registers at their highest bytes. Interesting effects can be expected, when the LOAD interupt vector changes due to advancing counters...

    A clock/SRAM would make sense as a CRU activated device, the SRAM could hold the DSR for clock access. Lower RAM addresses should be write protected to protect the DSR (accessible only for DSR updates).

AtariAge
Forums
Store
General
Follow AtariAge

Copyright ©1998-2021 AtariAge

×
×
  • Create New...