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Тема: ZX Spectrum - raining effect

  1. #1
    Master Аватар для VELESOFT
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    По умолчанию ZX Spectrum - raining effect

    More Russian software use IM2 vector table in slow memory area (16384-32767 and slow mem pages on ZX48/128/+2/+3). This ZX models contain HW bug in HAL10H8 chip and if high adress byte of vector table (register I) is set to this slow (contended) memory, ZX is very unstable and ULA show in screen raining effect. ZX will crash. This problem is possible correct in software by setting register I (IM2 table) to fast memory (or ROM). Exist fixed versions ?

    list of raining games:
    4x4 puzzle
    at4open
    black raven
    breditor
    death valley
    gambit
    hexagon 2
    imperia 3
    jackals
    netwalk
    sfort fxd
    snake demo
    spriter
    transword
    ufo 2
    viking quest 1, 2
    wolf demo 3
    sparrows
    deathmatch arena
    dizzy forever
    fast breed
    jackals
    shashki

    this games is download from my page:
    http://velesoft.speccy.cz/kmsoft.htm

    VELESOFT
    Последний раз редактировалось VELESOFT; 31.03.2013 в 01:38.

  2. #1
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  3. #2
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    По умолчанию

    You should understand that the Russian ZX and the EU ZX are very different and I think that correction is possible only for new games (or for games are being developed) but it's impossible for games which exist already because (as a rule) their developers left the scene..
    That would be great to add the information in the Dveloper's FAQ and recommendations

  4. #3
    Master Аватар для VELESOFT
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    По умолчанию

    Цитата Сообщение от Raydac Посмотреть сообщение
    You should understand that the Russian ZX and the EU ZX are very different and I think that correction is possible only for new games (or for games are being developed) but it's impossible for games which exist already because (as a rule) their developers left the scene..
    That would be great to add the information in the Dveloper's FAQ and recommendations
    I will fixed this games, this is easy. (rewrite I register to #80-#BF and write to new adress original 2B im2 routine adress)

    VELESOFT

  5. #4
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    По умолчанию

    Цитата Сообщение от VELESOFT Посмотреть сообщение
    I will fixed this games, this is easy. (rewrite I register to #80-#BF and write to new adress original 2B im2 routine adress)
    I mean that it will be very strange if you get any support from the developer's side (they are very lazy to change old working games )
    thus you just have to ask developers of the games for the correction and make it yourself

  6. #5
    Member Аватар для valker
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    По умолчанию

    Цитата Сообщение от VELESOFT Посмотреть сообщение
    I will fixed this games, this is easy. (rewrite I register to #80-#BF and write to new adress original 2B im2 routine adress)

    VELESOFT
    First of all you should find an unused space in #8000-#BFFF.. IMHO, it could be the most difficult part of your work.

    Thanks

  7. #6
    Veteran Аватар для bigral
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    По умолчанию

    Цитата Сообщение от VELESOFT Посмотреть сообщение
    ... This ZX models contain HW bug in HAL10H8 chip and if high adress byte of vector table (register I) is set to this slow (contended) memory, ZX is very unstable and ULA show in screen raining effect. ZX will crash...
    I thought "snow" effect is important feature of original spectrum and some games use it according to blog about HARLEQUIN clone development: http://www.zxdesign.info/dynamicRam.shtml

    What I'm wondering about is why machine crash happen? Is that because EI (enable interrupts) happen before actual interrupt handler completed? I thought only random screen glitches and music corruption may happen, but game should still operate somehow...

  8. #7
    Master Аватар для VELESOFT
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    По умолчанию

    Цитата Сообщение от valker Посмотреть сообщение
    First of all you should find an unused space in #8000-#BFFF.. IMHO, it could be the most difficult part of your work.

    Thanks
    Yes, but if memory #8000-#BFFF is used for main code, is possible transfer original code to old im2 vector table area(in slow memory) and to this fast memory write new IM2 table.

    VELESOFT

  9. #8
    Master Аватар для Conan
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    По умолчанию

    Цитата Сообщение от VELESOFT Посмотреть сообщение
    More Russian software use IM2 vector table in slow memory area (16384-32767 and slow mem pages on ZX48/128/+2/+3). This ZX models contain HW bug in HAL10H8 chip and if high adress byte of vector table (register I) is set to this slow (contended) memory, ZX is very unstable and ULA show in screen raining effect. ZX will crash.
    As I know the problem of crash (if the register I has a bin value 01xx xxxx) was fixed in ZX Spectrum 128 (+2) and later. In addition ZX Spectrum +2A/B/+3 has no snow effect at all.
    Another question is a different addressing of slow/fast pages (by the 7FFDh port) in Sinclair’s and Amstrad’s Speccies. Probably you called it “bug in HAL10H8 chip”.
    P.S. In ZX Spectrum (48K) a HAL10H8 chip never used.

  10. #9
    Master Аватар для VELESOFT
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    По умолчанию

    Цитата Сообщение от Conan Посмотреть сообщение
    As I know the problem of crash (if the register I has a bin value 01xx xxxx) was fixed in ZX Spectrum 128 (+2) and later. In addition ZX Spectrum +2A/B/+3 has no snow effect at all.
    Another question is a different addressing of slow/fast pages (by the 7FFDh port) in Sinclair’s and Amstrad’s Speccies. Probably you called it “bug in HAL10H8 chip”.
    P.S. In ZX Spectrum (48K) a HAL10H8 chip never used.
    Yes, HAL chip is GAL equivalent and is used on ZX128/128+2 only. In ZX128/+2 HAL set signal ULA A15 signal for access to fast/contended memory/ports. If you replace HAL with GAL chip and reprogram new correct equations + connect signal RFSH to unused pin 11, then remove raining effect.
    http://velesoft.speccy.cz/zx/umbrella/umbrella.htm

    New gal set ULA A15 to log.1 (= fast adress space) in refresh time. In same way is possible accelerate all contended ZX ports....

    VELESOFT

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