Announcement

Collapse

Forum Rules and Etiquette

Our mission ...

This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Rule 1: Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Rule 2: Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Rule 3: Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

Creative Music System (CMS) / Game Blaster compatible replica

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Creative Music System (CMS) / Game Blaster compatible replica

    Hello,

    I read about Creative Music System (CMS) / Game Blaster at Great Hierophant blog. This sound card based on two Philips SAA1099 chips and looks easy to duplicate. Easier than adlib: SAA1099 data lines to ISA data lines, A0 to ISA A0, Vref through 10K resistor to VCC, DTACK (open collector output) not used and pull-up with 10K to VCC, CLK from ISA-OSC divided by two by 74ls74 or another counter. First SAA1099 chip CS to address decoder 0x220 and second SAA1099 chip to address decoder 0x222. Thats all!

    But the most difficult - card autodetect. Great Hierophant write:
    The left SAA-1099 is at I/O 2x0 & 2x1 and the right SAA-1099 is at I/O 2x2 & 2x3. The subsequent twelve I/O addresses are used by the CT-1302. For a long time, the function of this chip was a mystery, but now we know what it can do. One problem which Creative used this chip to solve was that of detection. While the game publisher could require a user to tell a program the hardware he had in his system, it would be difficult for a less savvy user to know or remember what he had or where in the I/O space it was. Creative decided to make it easy for the consumer and the game programmers by allowing the card to be detected by software.

    In order for a card to be detectable in software in a PC, it has to give a reliable, non-random response to a read from the processor. The SAA-1099s cannot be read, only written, so there was no reliable way to detect these chips in software. Here is where the CT-1302 comes in. For the remaining addresses, 2x4-2xF, it will store or latch an 8-bit value written to it in one register, which is then read back by a program from a different register. If the values written and read match, then the card has been detected successfully. If they do not match, then the card is not detected. There must be two different I/O addresses involved, otherwise this scheme does not work reliably.
    I tried to emulate this method in emulator - data written to 0x224-0x22F port is stored to variable and then read back when access to 0x224-0x22F port, but some programs did not detect card. Then I looked at the source code of DosBox and I found this logic: data store only when 0x226 or 0x227 port write. Other port ignored. Data read back only if access to 0x22a or 0x22b port. Other port ignored. And last thing - when reading port 0x224, data allways must contain 0x7F:

    PHP Code:
    uint8_t cms_port_read(uint16_t addrvoid *p)
    {
        
    uint8_t res;
        switch(
    addr-0x220) {
        case 
    0x4:
            
    res 0x7f;
            break;
        case 
    0xa:
        case 
    0xb:
            
    res lastwrite;
            break;
        }
            return 
    res;
    }

    void cms_port_write(uint16_t addruint8_t valvoid *p)
    {
        switch(
    addr-0x220) {
        case 
    0x6:
        case 
    0x7:
            
    lastwrite val;
            break;
        }


    So, we need RAM to store 1 byte. I think i can use latch register. And i am looking the best way to do the decoder... Original card used 74ls138 2 pcs and 74ls139 1 pcs. At first approximation my circuit:



    /IOCS16 not used, this must be AEN signal..

    Any ideas or suggestions?

    #2
    Should be simple to do with a small CPLD or even a couple of GALs, no? For a one-byte memory TI/MMI made some LSTTL that looks like an LS374, but has read-back capabilities (74LS793/794), but those would be pretty hard to find now. TI also had some octal bidirectional bus registers (74LS651-4), but again, probably hard to find.
    Reach me: vcfblackhole _at_ protonmail dot com.

    Comment


      #3
      Originally posted by Chuck(G) View Post
      Should be simple to do with a small CPLD or even a couple of GALs, no?
      Yes, you right, but i haven't programmer for GALs. Moreover, PAL/GAL programmer circuits too difficult to replicate at home.. CPLD like Altera EM7064 is a good choice, but i want keep a "retro" style, so DIP-packages more preferred...

      Comment


        #4
        Most PROM programmers will also do common SPLDs like 22v10s and 16v8s. Also allows you to stick with 5V PTH target.
        "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

        Comment


          #5
          - No need to decode A10 and A11 for I/O ports, most ISA cards don't...
          - Probably no need to decode A0 either... Does it matter if both 0x224 and 0x225 will read as 0x7F?
          - I'd try to avoid 74154 because it is slow and large. If possible use 74LS138 instead
          - ~IOCS16 is not present on 8-bit part of ISA, and yes, I/O card needs to decode AEN signal (or bad things will happen with DMA).
          - It might be possible to save U3 and all the related decode logic. Just put pull-ups/pull downs right on the internal data bus. TTL logic has relatively high "LOW" level input current (0.4-1.6mA depending on logic family). So the pull down resistor should be 1k or even less (470 ohm?!). The pull-ups can be 4.7K, or even 10K...

          Comment


            #6
            Originally posted by eeguru View Post
            Most PROM programmers will also do common SPLDs like 22v10s and 16v8s. Also allows you to stick with 5V PTH target.
            Be careful there--I've seen some Chinese programmers that list the 22V10 as one of the devices, but it turns out that they can handle only the 20-pin GALs, such as the 16V8. That's one of the reasons I sold one that I had just purchased.
            Reach me: vcfblackhole _at_ protonmail dot com.

            Comment


              #7
              Thanks for pointing out the error, my blog entry has been updated.
              My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

              Comment


                #8
                Could be something like this:
                Game Blaster Address Decode.jpg

                The 74LS245 transceiver is enabled by addresses in 0x220-0x23F range (generated by the bottom 74LS138 ).
                The lower bits of address (A5..A1) are decoded by the top 74LS138. It generates chip selects for SAA-1099 chips and read/write enable signals for the 74LS374 flip-flop (I think 74LS574 FF, or 74LS373 and 74LS573 latches can be used instead).
                The pull-up and pull-down resistors drive the internal data bus (DB0..DB7) so the default value is 0x7F (that if nothing else drives it).

                Comment


                  #9
                  Thank you, but if it is possible put a bigger picture? I expect the arrival SAA1099 chips from China, during this time I can try to make autodetect...

                  Comment


                    #10
                    Originally posted by Tronix View Post
                    Thank you, but if it is possible put a bigger picture? I expect the arrival SAA1099 chips from China, during this time I can try to make autodetect...
                    Sorry about the image size... for some reason the forum software insists on converting PNG image to JPEG. Attaching a ZIP file with the orignal image. If you really want I can send you KiCad schematic as well...
                    Attached Files

                    Comment


                      #11
                      BTW, wouldn't it be simpler to hack a game and remove the detection code (and set it to a default value of 0x220, or use an environment variable)? It seems that the described detection method only works with the Game Blaster, but not with SB 1.5 / SB 2.0. So hacking the game will make it usable on these cards as well.

                      Comment


                        #12
                        Today i get some time to build CMS replica... I used mostly Sergey's circuit for auto-detect part except 10k pull-ups. If i read any empty port i get 0xFF value, so i think motherboard have internal pull-ups for data lines. Soldered auto-detect part from Sergey's circuit:



                        Did the test stand based on 386 CPU and install my device onto left ISA-slot:



                        And run TESTCARD.EXE from CMS diskette. So, this software successfuly found CMS:



                        Then i soldered two SAA1099 and 74HC74 for divide 14,3MHz by two. Audio outputs has not filtered, no amplifier. Just 1k pull-ups for all four output channel and then mixed by 10k resistive divider into left and right. Then output to headphones over 0,1mF:



                        It's worked! noisy, but work! I think needs to be done with the use of filter capacitors.

                        I recorded sound from this card:

                        Comment


                          #13
                          Sounds very promising, and I would think that if it replicates DOSBox's CMS detection methods, then it would work with every game that requires the Game Blaster autodetection to work.
                          All you Russians, first the Adlib, then the SSI-2001 and now the Game Blaster! Perhaps the Covox Sound Master will be next. Will no 8-bit sound card be kept exclusive and ludicrously expensive?
                          Last edited by Great Hierophant; May 24, 2015, 09:26 AM.
                          My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

                          Comment


                            #14
                            Originally posted by Tronix View Post
                            It's worked! noisy, but work!
                            Fantastic work, Tronix! Warms my heart to see the SAA1099 get some love.
                            Offering a bounty for:
                            - A working Sanyo MBC-775 or Logabax 1600
                            - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

                            Comment


                              #15
                              Nice work!

                              Audio quality: Adlib and SoundBlaster use active filters. Also the audio part is separated from digital, shielded (at least has a solid ground plane).

                              Not sure if reading an unused I/O address will always give 0xFF. Older computers (e.g. PC/XT) normally don't have pull-ups on data bus. And 0xFF might be a side effect of TTL inputs reading '1' when connected to Hi-Z state outputs. So I recommend put these pull-up resistors.

                              It is interesting to see some soviet/Russian chips on your board.
                              BTW, K155TM2 is an old plain TTL 7474; K555 series are 74LS analogs; K1533 are 74ALS.

                              Comment

                              Working...
                              X