Catch Me if You Can

Seems like everybody is ditching their Intels, with new security issues found every day. I got into that mood as well and decided to retire another i386, a DX this time. Obviously it wouldn’t be any fun if it wasn’t soldered to the motherboard 🙂

And the replacement is a TX486DLC, another Cyrix in other words. I had to write my own cache configurator for the different memory map a full 32-bit Towns has, but I’m happy to report that both the CPU and the program work fine.

Benchmark results are pretty much identical to the 486 Marty, though this CPU doesn’t have a clock doubler so it’s still a 16MHz system. I know some people opt to change the clock generator to overclock it a bit but I decided not to. With cache enabled and possibly RAM timing tweaked it’s plenty fast for that machine already – twice faster than the 386 in fact.

I’m almost done shipping group 1 Phoebes so now I’ll have a week or two to fully dedicate to DocBrown. BTW, another Rhea batch will be ready soon as well, as usual watch the blog for ordering window announcements.


35 thoughts on “Catch Me if You Can

  1. Thanks GDEMU – can’t wait for “DOCBROWN” and the rhea batch

  2. GDEMU
    Thanks a lot about your GDEMU ODE and my upcoming Phoebe.
    Well, I wish to you a huge success for you, it was a great pleasure to follow your exciting blog.
    Now, I have what I needed to develop video games on these consoles. Now, it’s time for me to begin my works.
    I wish to you a good continuation…

    Thibault Baldetti

  3. When will we start seeing DOCBROWN invoices appear?

    How is the ODE for the Towns Computer coming along?

    When will that batch be up for order? I have a Towns II tower I with dead CDROM drive so would be helpful.

    I found the same 486 you used in your Marty Swap. Any advice? Or just Desolder old 386 and solder on the 486?

  4. I second the above comment,

    Got a “i was on list” for Doc Brown, but never got a paypal payment request. Submitted my proof of ownership, but told to wait.

    How to proceed from here?

    Also i am in the 2nd group for Pheobe…..i imagine a payment request would arrive before DOC Brown?

    Thanks GDEMU

    • Invoices will come when he is ready.. I was just inquiring, since he said he would be working on DOCBROWN after phoebe round 1 was over, if that meant he was just working on the boards or if that meant invoices were coming too.

      I think everyone who submitted a preorder and proof of ownership has been waiting a very long time now (3 months since pre orders window opened) . After he stated that he was going to rework some of the security of the devices (starting with this one) after the whole gdemu debacle with clones and such, we all know it was going to be a long time.

      I am just curious if that 1-2 weeks he is working on docbrown means invoices and shipping of the cards or if that means he will build them in the 1-2 weeks and then we have to wait for either round 2 of phoebe or the Rhea batch before we see invoices and shipping.

  5. Nice work!
    I’d be willing to provide you with a Cx486drx2 if you’re willing to help me set up a cache utility for the tower towns. It’s got an internal clock doubler and cache.

  6. Wish you did a Sega CD ODE, model 2 or JVC X’Eye version would be amazing.

  7. Applause for you my friend like always very appreciate it. Let me know when it is ready. Doc Brown for Towers or Marty any upgrade is great welcome. My money is yours.


  8. Thank you sir for all you already done ! I think i will come in the Towns Marty world too but i need a source to grab the a games collection…. i didn’t find one until now ^_^ ! Wish you a great weekend!

    Kind regards,

  9. How can I order a phoebe I’ve been checking for months 3-4days a week and it’s always closed.
    Oh well I guess

  10. Awesome, i’ve thought about switching out my 386, but damn the pitch of those pins…don’t want to wreck my motherboard. Is it worth it?

    • I am gonna try.. I will let you know.

      Got my Flux
      Got my solder.
      Got my Wick.
      Got my hair air machine.

      Gonna give it a real good professional Go.

    • In general you need some proper tools for this job. I have a cheap BGA rework station (preheater+hot air) and some experience, though this kind of chip package was new to me.

      It can be done with a quality heat gun assuming you’ve got experience in controlling the temperature, otherwise you’ll just burn/melt someting.

      One of the issues you’ll face is how to clean the holes of leftover solder.

      • Yea.. BGA package and reballing is not my thing.

        I was referencing changing my 386 out to a 486 on my Marty.

        That looks a bit more doable for me. Removing the old 386 should be simple and cleaning up the pads should be easy too. With some Kester no clean flux and some nice .50 desolder wick. Preparing it for the 486 should be pretty simple. The hardest part will be lining up the new 486 and soldering a single pin on 2 or 3 sides to keep it in place. After that it all about solder Dragging across all the pins and using a crap load of flux to make sure there are no bridges. A really good magnifier will be helpful too.

      • I have a pretty good hot air rework, but I think I would prefer to practice a bit on something similar, would hate to wreck the board for small gains. Probably be easier on my nerves to just pick up a pentium based Towns 🙂

  11. Hello,

    I contact you because since several years I have a FM Town Marty with a « defect » CD drive. I never found the issue that makes this drive not working. I changed all capacitors on the drive board.

    The drive act oddly. First it make a buzzing sound. This sound change when i turn manually the CD spindle. The motor of CD spindle, even if the tray is open, seem to be powered. It does’t turn but has a sort of « resistance ». It move (shake) very shortly but continually by left/right motion. When a CD is in tray, the drive spin but can’t read the disc. I notice the buzzing sound may come from the motor driver.

    – I don’t know if the buzzing sound and spindle motor resistance is normal.
    – I don’t think the issue come from the laser lens. The laser light up.

    Have you some advice to help me to fix this Marty CD drive ? Or some spare part of the CD drive ?

    Thanks for your help.

    • IIRC the spindle motor is just a standard DC one, not a star-type servo. Either way there has to be a chip that controls its rotation speed since that’s always a bit off (and depends on the head position, it’s CLV after all). That chip gets correction signal from the bitstream processing so that it can properly sync to that.

      My guess would be either that chip is faulty or the bitstream processing is. How long does the drive spins a CD before it gives up? A couple of seconds or more? Or does it stop spinning after 1 revolution or less? If the spin is long then the bitstream processing (and laser/sensor) would seem to work but due to wrong roation speed it won’t lock onto the signal.

  12. Thanks, your help is very appreciated. The CD spin up during approximately 30 second before its stop. Sometime, very rarely, its load something but the system crash after this loading.

    I think the issue come from the motor driver 8388SR, but I can’t found a spare part or equivalent (pin to pin compatible) on the Web. I also found similarities with old BUS 2x CD-ROM drive like Panasonic CR-562. Maybe these drive use the same interface than Marty…

    • Truth be told these drives are POS anyway, even when work. This particular design was based on some older CD-player but I can’t remember the brand/name now.

      One more thing though, make sure your Marty PSU delivers stable 9V as the drive uses this for the motor power.

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