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Thread: Show us your Tandy Computers!

  1. #181
    Join Date
    May 2011
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    Quote Originally Posted by rlauzon View Post
    tl;dr
    The gate array units were designed so that they would be backward compatible.
    Are there "Gate Array" and "non-Gate-Array" 4Ps? The Desktop 4 was introduced a few months before the 4P in 1983 (April vs. September), and according to the web-lore they replaced the original motherboard which was mostly discrete TTL logic with a few PALs with the higher-integration gate array model sometime in late 1984. The 4P was discontinued in early 1985; it used a different motherboard than the 4.... So, okay: according to the TRS-80 4P service manual there *were* both gate array and non-gate-array versions. I did not realize that. Now I'm wondering what version mine is.

    So far as I'm aware there's no functional/behavior differences between the gate array/non-gate-array versions of the 4, it looks like from the manual that probably applies to the 4P as well. The desktop 4s of either type don't need the Model III ROM image to be present on the disk to boot into Model III mode, they have the ROMs built in, while all 4Ps just have a little 4k boot stub. (The reason why is the desktop 4 was available in a cassette-only configuration until quite late in the product's life for use in schools. Without a disk controller it behaved exactly like a Model III.)

    Quote Originally Posted by blackepyon View Post
    One of the guys at my local retro-computer club brought a 4P for show-and-tell the one time. I was intrigued that it has the same style keyboard as the earlier Tandy 1000 models.
    It is shaped remarkably similarly to the Tandy 1000/2000 keyboard (in particular it has those distinctive rotating feet thing on the back). The actual key layout is of course different. (The 4P has the same layout as the later desktop 4s; the first ones had the cursor keys arranged like a Model I's instead of in the inverted T shape.)
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  2. #182
    Join Date
    Jun 2015
    Location
    Sioux Falls SD
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    366

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    The first 4Ps were non-gate array. First with B?W screens, then with green screens, then came the GA, all with green screens. The non-GA 4P has the arrow keys similar to the Model I keyboard. The GA 4P had the arrow keys clustered on the lower right side. The biggest issue with the non-GA 4Ps was a tunable capacitor for 80-column mode. Occasionally, 80-column mode became unstable, and the capacitor was the culprit. Ira's site used to have instructions to adjust the thing. You had to disassemble the unit, and they stuck it way at the front of the board. But for normal operation, the non-GA and GA machines performed the same.

    I had both versions with green screens. The GA machine had a brighter display than the non-GA. Not sure if that was just my machines or if that was a characteristic.

  3. #183
    Join Date
    Jan 2014
    Location
    Western North Carolina, USA
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    For the 4P, the only way to know for sure which board you have is to look at it. Looking through the modem slot directly above the RS-232 connector, the gate array version shows two large 40 pin chips side by side right below the connector in the modem slot; the non-gate-array version shows one large 40 pin chip directly behind the RS-232 connector, and a second 40 pin chip under the right side of the modem slot and farther away from the connectors.

    As far as I know, installing a non-GA board for a 26-1080 into a 26-1080A chassis is fairly easy to do, and so even if the chassis is a 26-1080A, with a green screen, clustered arrow keys on the keyboard, and plastic latches for the cover, as far as I know it could still be packing a non-GA board, just not from the factory.

    Not so for the desktop 4, where looking at the RS-232 connector's location is definitive; for the non-GA the RS-232 exits the bottom of the machine, but on the GA version the RS-232 exits the back of the machine. Neither screen color nor keyboard layout is definitive.

    There are some subtle timing differences between the four 4's, mainly in the area of video RAM wait states and access timing, which probably have been benchmarked before. I do remember that David Dalager told me back in 1990 that his non-GA 4P was his best performing overclock.

    I took photos thought the modem slot of one of my non-GA 4P boards and my one GA 4P board, but they're too large to upload; it'll have to wait until tomorrow for me to crop and thumbnail to fit the size limit, so I'll try to upload then.

    The one difference that can be determined from software is the non-GA version's use of the FD1793 floppy controller, versus the GA version's use of WD1773. While the 1773 is supposed to be identical in operation to the 1793, there are edge cases where the behavior is different and can be checked in software.
    Last edited by lowen; January 22nd, 2020 at 06:21 PM.
    --
    Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"

  4. #184
    Join Date
    May 2011
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    Quote Originally Posted by lafos View Post
    The first 4Ps were non-gate array. First with B?W screens, then with green screens, then came the GA, all with green screens. The non-GA 4P has the arrow keys similar to the Model I keyboard.
    It was gnawing on me after thinking about that something didn't look quite right after checking out the photo of the "Gate Array" 4P and, lo and behold, I'd apparently forgotten that my machine does indeed have the old-style keyboard arrow arrangement. (Clearly I need to take it out more often to play with.) It also has the white mono monitor, so I guess it must be a relatively early one.

    My desktop 4 has the old-style KB and non-GA motherboard, but it does have the green screen.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  5. #185

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    I have a Model 4P which I purchased new during the closeout sale when they were being discontinued. Mine is non-GA but has a green screen, plastic cover latches and the clustered arrow keys. I did bring it in for warranty work when it was a few weeks old as the video was unstable/severe flicker periodically. I don't believe it had the motherboard replaced - I thought it was just a wiring harness issue - but possibly it did get a different board which may explain this combination. Personally I would rather have the non-GA since the parts are still relatively available where the GA custom chips you would pretty much need to find a parts system as a donor if any of those chips failed (but it seems they are pretty durable). I do have a GA version kicking around purchased used many years ago that never worked - I think it has a power supply issue (when powered on, after a few seconds it makes a very loud popping sound and the display never lights up/drives do not spin). I bought it for the stuff that came bundled and never got around to looking at it.

  6. #186

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    My final latest Restoration and upgraded creation;
    1982 TRS-80 Model 3, with 16K, diskless system to: 48K of RAM, 360K FDD, Gotek USB FDD, Hard Drive: FREHD internally mounted on custom 3Dd printed bracket, 2 watts amp w/2" speaker, R/S OEM High Res Graphic Card (512x192 pixels), update the power cord assembly from "rat tail" to modern connection, among other little works was done, recapped power supplies, rewired most of case, and professionally colour matching, repainted case color. so Here are some of the phots I leave you with, Ill answer any questions you may have.

    From Rat Tail to modern connector.


    Half heights; 360K Teac Drive and Gotek fitment and mounting


    FreHD in 3d printed Custom Bracket and passing of the 50 pin cable internally, with modded BIOS chip for auto boot to HDD


    2 watts Amplifier with 2" 3w Speaker, no more need for an cassette player to hear sound in the games


    3 cooats of primer later....


    3 coats of paint, color compare side by side to an oem case (left)


    And finally restore, Re-Assembled in it "off the shelf" new life.
    Last edited by Patrick Bureau; January 26th, 2020 at 06:28 AM. Reason: typos
    Vintage: TRS-80 MODEL 4, 128K RAM, 360K & 720K FDD, Gotek, FreHD, GURU RS232-WIFI MODEM, DWP-510.
    Web Site: https://texastandyrestoration.com/
    Programmer Inspiron 660s, I5-3330s, 8GB Ram, 1TB HDD, BK-844USB & EP-2A-88.
    Workstation: Optiplex 7010, I5-3470s, 8GB Ram, 1TB HDD.
    Gaming: i7-8700K, 16GB, 1TB SSD, RTX 2060, Dual 27" LG IPS Monitors.

  7. #187
    Join Date
    Feb 2017
    Location
    Chilliwack, BC, Canada
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    525

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    Ooooh! Fancy!
    My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

  8. #188

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    Damn, that looks amazing!
    My Retro Collection:
    CBM: C64, Amiga 500 x2, 600 & 1200
    Apple's: IIc, Mac SE, LCII, LC630 & Power Mac G3/233 Desktop
    PC's: K6-III+ 500 System + Roland MT-32 & Tandy 1000 EX 640kb, 3.5" FDD, CF-IDE 4GB HDD
    Visit my Tindie store for Tandy 1000 Adapters for EX, HX, SX, SL, TX & TL etc

  9. Default

    Newest member in my collection. Currently, only HxC emulated double disk drive.
    Working on getting the real 5.25" floppy connected soon.
    I also have an M4 with FreHD.
    DSC09540.jpg

  10. #190

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    aww gotta love a clean looking Model 1.. but what monitor are you using ? ( asking because I dont have one either)
    Vintage: TRS-80 MODEL 4, 128K RAM, 360K & 720K FDD, Gotek, FreHD, GURU RS232-WIFI MODEM, DWP-510.
    Web Site: https://texastandyrestoration.com/
    Programmer Inspiron 660s, I5-3330s, 8GB Ram, 1TB HDD, BK-844USB & EP-2A-88.
    Workstation: Optiplex 7010, I5-3470s, 8GB Ram, 1TB HDD.
    Gaming: i7-8700K, 16GB, 1TB SSD, RTX 2060, Dual 27" LG IPS Monitors.

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