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Thread: Tandy 1000 TX with PK-X486/87SL5-1 upgrade: speed that I need

  1. #1

    Default Tandy 1000 TX with PK-X486/87SL5-1 upgrade: speed that I need

    Hello, all.

    I recently picked up a "spare" Tandy 1000 TX, and decided to try an upgrade I didn't want to "risk" on my primary TX: I purchased a PGA socket extender, hoping to install a backward-facing PK-VF486/87SW2 upgrade CPU. Of course, the computer refused to boot with the extender in place, regardless of which CPU I tried. Damn. Since the PK-VF486/87SW2 can't clear the nearby IC without it, I decided to go in a different direction (very literally).

    The other TX machines I've owned have a large capacitor in the front of the case, near the CPU socket. Not so on this particular motherboard, which has that large capacitor off to the left of the CPU socket. This meant I could plug in a PK-X486/87SL5-1 upgrade without said capacitor getting in the way. Unfortunately, using this upgrade would require cutting into the case to provide clearance for the rather long board, because the case DOES get in the way. D'oh! But before I sliced into anything, I decided to prop up the motherboard a little and test the upgrade. Success!!

    Next I set to "defiling" the front of the case. This is what it looks like now:

    (Note the faint of heart may wish to avert their eyes.)

    tx-upgrade.jpg

    (Yes, I realize I really need to dust inside there.)

    This is a satisfying upgrade for me. I really like the TX, but even with the Make-it-486 installed it just never had enough pep for my tastes. Here's a Topbench benchmark comparison to illustrate results this upgrade delivers...

    Stock TX: 15
    TX with Make-it-486: 24
    TX with PK-X486/87SL5-1: 50


    The PK-X486/87SL5-1 cache is enabled via REVTO486.SYS, which can always be disabled in order to run the machine at a speed certain games may prefer. In particular, my research thus far has shown that several games refuse to correctly display Tandy graphics when the cache is enabled: Ultimate Golf and Windwalker. This applies to both the PK-X486/87SL5-1 and the Make-it-486 (the latter of which uses DO_CACHE.EXE instead of REVTO486.SYS).

    Why would anyone do this upgrade? I enjoy experiencing games that support Tandy sound (music), but some of the later ones require speeds that the TX -- my favorite of the 1000 line -- isn't quite capable of w/o a little help. For various reasons, the TX is my go-to machine for Tandy graphics & sound, so I really wanted it to be more of a speed demon. Now, it is. I don't think I'd be able to get it cranking any faster than this.

    So, that said, I've shared the info here in case anyone else out there is seeking a quicker Tandy 1000 TX --> even if it means "performing surgery" on it.

    BTW: On an unrelated note you'll notice I'm using Manila Gear's No Slot Clock in this machine, to keep time/date. This product was engineered for the Apple II, but can be used in the TX by way of an IC socket placed between it and the motherboard. This isn't a cheap solution, and requires both CR2032 batteries, but at the time it seemed the quickest and easiest solution for me.
    Last edited by DeathAdderSF; January 31st, 2019 at 10:59 PM.
    Cruise by Diskman Presents: filled with geektastic classic gaming goodness!

  2. #2

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    Awesome! I love these upgrades. I just upgraded my RSX with a Make it 486 Cpu.

  3. #3

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    They're very handy. Especially when you're dealing with a computer that offers unique hardware, like the Tandys. Really gets you more enjoyment out of the machine. I can't wait to have a little free time to really indulge in this particular upgrade and see what it's truly capable of.
    Cruise by Diskman Presents: filled with geektastic classic gaming goodness!

  4. #4
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    Being a 1000SX fan, I am very envious. Good job!
    Surely not everyone was Kung-fu fighting

  5. #5

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    Quote Originally Posted by Agent Orange View Post
    Being a 1000SX fan, I am very envious. Good job!
    Well I've sampled virtually the entire Tandy 1000 lineup and found that no one computer in the series does 100% what I need it to. There's always one or more little nagging things about each model that I can't quite live with. (Explaining that would take a long time, so you'll pardon me if I skip it.) The TX isn't perfect either, but it came the closest. So I am doing my best to outfit it as best I can to suit my needs.

    BTW I noticed something new about this upgrade: With the PK-X486/87SL5-1's cache enabled, some games are unable to detect or display Tandy graphics. This has only occurred with two games so far, that I've tried: Leisure Suit Larry 1 and The Simpsons Arcade Game. LSL1 reports an "OVERFLOW ERROR" and locks up, whilst Simpsons just doesn't "see" Tandy mode so it drops to DOS with a, "This game requires an EGA, VGA or Tandy display" message. With cache disabled, both games can find and use Tandy graphics. When a VGA card is installed, these games can use EGA or VGA just fine. So this issue seems to be related either to the speed of the machine when cache is enabled, and/or the detection and display routines of these particular games. All the other games I've tried so far have no problem.

    The Simpsons Arcade Game is weird anyway, in that it won't detect/use Tandy graphics if 768kb of RAM is installed (good thing the TX has that jumper). Nor will it allow Tandy sound if it detects ANY OTHER sound card. (It greys out Tandy sound in the config program. If you hex edit the CFG to enable it, the game refuses and forces you to make another choice. Some programmer really didn't like Tandy sound!) So I tend to think the problem with this game is just poor or restrictive programming. Not sure what's causing the LSL1 problem, but it doesn't "bug" me: Part of this hardware tinkering that I enjoy -- if you can believe it -- is doing compatibility testing. I like to see the results of trying unexpected things, and documenting the result.
    Cruise by Diskman Presents: filled with geektastic classic gaming goodness!

  6. #6
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    DeathAdderSF:

    My experience with 1000SX goes back over 30 years. I know I'm the odd-ball here because I never did care about Tandy graphics and sound. I still have a mono sound card installed as well as a generic VGA card. I never cared for CGA and got an EGA monitor and card as soon as I could afford it. But, I did try to "take it to the limit" with a NEC V20, SCSI HD, RTC, 640 K, and a 3.5" floppy. In between all of that there has been an ST-225 and the forums' own XT-IDE controller. With all of that being said, I believe the 1000SX is the most versatile PC that I've ever owned. Let us know what's next.
    Surely not everyone was Kung-fu fighting

  7. #7
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    I would love if you could explain what wiring changes you needed to make in order to get this to work on your 1000 TX. I've looked online on where I could find one of these PK-VF486 units, but am coming up empty so far. I wonder if they were fairly common or not..

    Thanks!

  8. #8

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    Quote Originally Posted by Agent Orange View Post
    I know I'm the odd-ball here because I never did care about Tandy graphics and sound.
    Whereas to me, Tandy gfx & sound is the #1 reason to own a Tandy 1000. I certainly wasn't knocking the machines in any way in my prior post. I just tend to have very specific needs when it comes to computers, and it's tough to find a "perfect" balance where Tandy sound is concerned because you have so many different factors going in terms of hardware and software.

    Quote Originally Posted by mojorific View Post
    I would love if you could explain what wiring changes you needed to make in order to get this to work on your 1000 TX. I've looked online on where I could find one of these PK-VF486 units, but am coming up empty so far. I wonder if they were fairly common or not..
    The blue wires and added resistors that you see in the photo weren't done by me. It's been suggested here (in a different thread) that those were simply "fixes" done inhouse to get an otherwise non-working motherboard out the door. The previous owner of the computer has no answers for me. Really, I am going to just assume that the upgrade I'm using is compatible with any TX. You'd just need to find a motherboard that doesn't have the large capacitor directly below the CPU socket.

    These particular CPU upgrades were made for the NEC PC-9800 line, which are Japanese computers. They just happen to work with our PCs because the architecture is so similar. I don't think you'll have much luck searching for them in the west.
    Cruise by Diskman Presents: filled with geektastic classic gaming goodness!

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