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Philips :YES

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    I've now scanned my four :YES manuals:
    • Getting Started
    • User Guide
    • DOS Plus User Guide
    • MSDOS 3.1 User Guide

    If anyone would like a copy, let me know.


      I've just read this post out of curiosity. The earlier reference to not being able to run PC disk drives any be because the PCs started using DiskChange that took over the DiskReady signal.
      The signal can be recreated by a retriggerable one shot, triggered from the index pulse OR'd with the read data. The one shot would time out after one revolution time.



        sorry for reviving the old thread yet again. I noticed that the expansion card seems to support both 4164 (16 chips) and 4464 (4 chips) configurations for its 128 KB of memory. Mine is populated with 4164, but since the BIOS supports a 640 KB configuration, it may be possible to replace them with 41256 chips instead.

        So I went ahead and replaced the D4164C-2 with KM41256-12 (and KM41256AP-12), and ... the system still reports 256 KB total memory. There are different jumper areas (for soldering) on the card. J3 is labelled "MEM SEL", the others are not labelled. Does anyone know how this card needs to be configured for the 512 KB configuration?

        Best Regards,


          I don't think it is designed to take 41512 chips. You'll likely only see the 128K, with those chips. It may only do 256K but I'd be suspicious of that.


            The BIOS specifically checks for 128 KB (base), 256 KB (base+128 KB) and 640 KB (base+512 KB) memory size, so I assume that the system designers planned for such an extension. (I don't know of any other expansion card ever made for this system.)

            In any case, the additional address pins are connected together, making me hope that 41256 chips will work. Without resoldering the jumper areas, the chips currently work as 128 KB instead of 512 KB... but without schematics, I need to trace the connections first to see what to change.

            Do you have any additional information on this system?


              No. Often for a single card, it is not done. It likely expects multiple cards.
              It might need a change of the address mux as well. I know that for the Olivetti M20 it requires changes at the address mux. Ir does 256k without any change but needs different addresses at the mux.



                I can now report success.

                Jumper bridge J5 next to IC 7003 (type 74F14N) selects between "128k" (bottom) and "512k" (top). After replacing the 4164 chips with 41256 chips, this bridge needs to be moved to detect 512 KB of memory. After tracing a rather large amount of circuitry on the board, I also found two AMPAL16R6DC, of which one is related to DRAM address decoding.

                With graphics mode disabled, chkdsk now shows 632 KB total memory:
                    728064 bytes total disk space
                     38912 bytes in 2 hidden files
                     58368 bytes in 8 user files
                    630784 bytes available on disk
                    647168 bytes total memory
                    604160 bytes free
                When graphics mode enabled, chkdsk reports 575 KB total memory:
                    588800 bytes total memory
                    540928 bytes free
                Best Regards,



                  the success I reported was too early, and I apologize for the misinformation. The BIOS does not actually test memory at boot and since most of the software provided with the system works fine in a 128 KB configuration, memory above 256 KB is rarely accessed. I wrote a small memory test program in assembly language to verify this.

                  In any case, the solder bridge J5 can be switched between "128k" and "512k" and will only affect the amount of memory seen by the system. Trying to access memory beyond 256 KB will hang the system. When using 41256 DRAM chips, the solder bridge J3 (labelled MEM SEL) needs to be moved towards the connector as well.

                  In the attached picture, solder bridge J5 is in the bottom center/left, while J3 is in the bottom right.

                  Note that overwriting the beginning of physical memory will freeze the system, even when interrupts are disabled. Some BIOS interrupts, notably int 10h, will happily enable interrupts and the next timer interrupt will crash the system if the vectors have been overwritten. Touching the end of physical memory will cause the screen show interesting corruption and freeze the system as well. It appears that not only VRAM is located in this area, but also some vital information for the graphics subsystem.


                  Best Regards,


                    Hello again,

                    after the PSU blew a RIFA cap, I opened the machine again and used the opportunity to read out all three ROM chips on the main board.

                    The BIOS ROMS are "(c) 1984 Digital Research, INC." and the files YES_23484.BIN and YES_23494.BIN contain the even/odd bytes.
                    The font ROM is "(c) PHILIPS 1984" and contained in YES_23494.BIN.
                    Also included in the ZIP file are pictures of the ROMs, showing both the copyrights and the numbers.

                    Best Regards,
                    Attached Files


                      Interesting font ROM -- there are two font sizes (8x10 and 8x but they're not using the same codepage. And the second font begins with what look like teletext graphics.