Tandy TRS-80 Model 4 Retro Computer Introduction and Teardown
Ғылым және технология
The Z-80 based TRS-80 Model 4 was the most expensive computer you could actually see and touch in any local Radio Shack store. In this video I talk about the machine, give a quick tour of how to operate it, and then I open it up to show you what is inside.
Would you like to see more content like this? If so, please consider supporting me on Patreon. / retrologiclab
Пікірлер: 85
Somewhere around 18:30 I say that the Apple II used a Z80. That's not correct, not sure what I was thinking!
@SpearM3064
6 жыл бұрын
To be fair, there *was* an expansion card, the Microsoft SmartCard, for the Apple II that had a Z80 on it, so you could use it as a CP/M machine. Maybe that's what you were thinking of. (In fact, it was Microsoft's first hardware product, and was staggeringly successful, selling 5000 units in just 3 months.)
@rhymereason3449
5 жыл бұрын
Yep, I was going to mention that the Apple II was a 6502 machine...
@colinwilcox4266
5 жыл бұрын
6502 wasnt it?
Nice to see this review ! I worked for a small company in the Netherlands that did all kinds of mods on the Mod4's. We started with the model 1, then the 3, and finally the 4. We made and sold them mainly for administrative purposes, working closely together with a plumber who was quite a programmer too. Of course we deemed those belt-driven floppydrives a disaster, and the first thing we usually did was to replace them with half-size double sided direct drives, mainly from Mitsubishi. We only used TRSdos on plain vanilla systems, we preferred NewDos80 for the more advanced stuff. We also thought that having room for more drives would give the possibility to put two harddisks in it. But that wasn't easy. We knew we had to use a "host interface" (now called a harddisk controller) to get any harddrive going. We could get those host interfaces (for a fraction of the cost of Tandy's), and screw them in at the back of the case, but the culprit was the PAL that was not there. Now we could buy them from Tandy of course, but they were so expensive ! So we decided to hire a part-time genius, who bit by bit figured out what that PAL would have to do to connect the bus to that host interface. After several tries, and a lot of time with the guy playing with his locic analyzer, we finally got something. So we got us some empty PAL's and programmed them ourselves. They worked perfect ! And there we went off selling them with our host-interfaces and harddisks for a fraction of the price of Tandy. And of course making a lot of money on it. It didn't get unnoticed by Tandy though, as we sold (a lot) more harddisk expensions then they did. And of course, one day we got some lawyers at the door to shut down our piracy operation. But we didn't pirate anything ! That PAL was our own developement, besides, you can't copy a PAL when the last fuse has been blown out. So we offered that we had our code compared to their code by a third party, and determine if we copied anything. Tandy agreed, and after a short while, we turned out not to have copied anything, our code was not only totally different from theirs, it was more reliable and faster too. From that moment on, we had a pretty good relationship with Tandy, getting serious rebates, and also doing repairs for them that they couln't do themselves. Ah, the days that some clever cowboys could still make some money ... :-)
@XAWZ
4 жыл бұрын
Cool story.
@jankoevoet4042
4 жыл бұрын
@@XAWZ Days long gone i'm afraid :-)
@BlackEpyon
2 жыл бұрын
How very kind of them to assume that you had pirated Tandy's stuff, instead of thinking that maybe somebody managed to figure it out on their own.
@jankoevoet4042
2 жыл бұрын
@@BlackEpyon Not so strange, and we didn't feel harrased or anything. We 've actually expected this to happen. After all, piracy was a common thing back then. In fact, we would have been surprised if they would NOT have taken notice and investigate our development.
The Model 4 was my first computer. I remember doing the 128k memory upgrade. It also involved soldering a jumper cable, I was 17 at the time and didn't have a lot of soldering experience. It was kind of terrifying, worrying about frying something with my soldering iron. But it worked, and I had a 128k Model 4. Of course, I really didn't have anything to utilize the extra RAM, but I still felt pretty cool. :)
@Blacklab412294
3 жыл бұрын
Mine was upgraded to 256K with two disk drives.
I love watching you man. Hope I'll find a passion in embedded engineering and programming someday in the future myself ❤
I just bought a Model 4 today, 2017-09-23. So much fun to time warp back to my early youth while playing with it!
@RetroLogicLaboratory
6 жыл бұрын
Awesome you found one! Any problems with yours or is it pretty much a fully working unit?
Thanks for making this video! The TRS-80 Model 4 is my all-time favorite design :)
This channel deserves way more subs than it has! Really enjoying this.
i worked for Tandy in the 1980's as a manager at a Computer Service Center.. Texas Peripherals drives were sold as after market replacement drives.. Tandy used Shugart or Tandon drives..
Actually, I believe most of the Radio shacks did have a Model 4 hanging around during the 80's. Before I purchased my own, getting a $2,000 loan from my local bank, I used to go in to the local store and used their Model 4 to write my games. Some times I was there all day till closing time. Back then their receipts were still had written and at the end of the day they, I mean I, used to manually enter the sales receipts into the Model 4 and transmit them over the phone line to Fort Worth TX, the home office.
Wow, I remember using this computer in my younger days ... it was so exciting to use at the time, and the floppy disk save/load, etc.
This stuff is sooo simple..That relay was for the cassette interface.
I had a Model 4 in 1982, I know because I had it before we moved to a new house. Mine was upgraded to 128 k and three floppy drives, couldn’t afford the hard drive. Mine had the black and white screen. I also had wide dot matrix and daisy wheel printers.
Regarding the lack of shielding on the TRS 80 I and the FCC complaint - in High school where we used them circa 81-82, we would load a game and then set a portable radio up next to the computer set to an AM station (or maybe it was FM - I forget which now), which the signal from the TRS 80 would jam . When ever we "fired" there would be a corresponding sound so we could get some kind of sound effects from the TRS 80 I.
I'm still so surprised that the build quality on older computers was crap back in the day compared to today's pc's....they don't build em like they used to...thank heaven...
If I remember correctly, J10 is where I plugged in my hi-res board back in the day.
A fluorescent light was used for a timing reference since the power was 60Hz.Us 50Hz Europe. These drives depended on ac line frequency to adjust the timing. Please dont think im being arrogant or bold. I know this old school stuff. You’re doing just fine.
@AtariFTW
4 жыл бұрын
I think you have it backwards. The drive runs on D.C. The 50 and 60 HZ markers were for the frequency at which the florescent lights were operating at. A florescent light operating at 60hz will make the 60hz indicator on the drive appear to be stationary when the drive is spinning at 300rpm.
@rickhunt3183
4 жыл бұрын
@@AtariFTW of course the drives run on dc.the timing marks were used to set the correct speed using the 60 Hz frequency of a florescent light as a reference. if the timing of the drives were wrong discs would not be comparable between machines. I'm sure you know..it's all simple stuff.
@rickhunt3183
4 жыл бұрын
@@AtariFTW When the drive speed is correct it. The timing marks will appear motionless.
Model 3 and 4 are my favorite!
There was a clock you could buy that was NOT Tandy that used a coin cell to power it so it would not loose time. The PIO Time board was made by a company in NY. Same company also made an actual PIO card that would control 16 relays and 16 4N25 inputs. Tandy made a Plug'n'play light controller for the Z-80 Mod 4 that used the cassette as a way to communicate between the light controller and the computer. The funny thing, I, with out knowing what the Peeks and Pokes did, I was able to rewrite their program so to be able to control more then one light at one time to dim, bright or on/off at the same time. X-10 never figured out that might be a desired thing to allow on their own product. As far as I was concerned that was one of the many things that killed the X-10 controllers.
Excellent presentation. Thank you for putting this video together.
I remember taking first computer lessons with TRS-80 in 1980-1981. Computer lessons were voluntarily then no degree was given to school report
We had these in our high school back in 1990-1991 for a BASIC programing class. ;) Oh the nostalgia. I failed the class by the way. lol! It helps if you don't skip class too much. lol!
1. U21 (HM6116p-4) is 4016 200NS RAM 2K X 8 Static (U21) and U23 next to it is a MCM68A316E Character Generator (U23) Tandy 8044316 2. J10 is on Page 20 of Model 4 Technical Manual "The graphics connector, J10, contains all of the above interface signals, plus CRTCLK, the dotclock signal, a graphics enable input, and other timing clocks which synchronize the graphics board with the CRTC." 3. the blue "chip at RP4 is Res Pak, 27 ohm, DIP 16-PIN (RP4) 8290027 4. Y1 and Y2 crystals: (pg56 of M4 technical manual) 4.1.5 is your 4Mhz cock. A 4MHz crystal oscillator and a divide by 2 and divide by 4 counter generate the clock signals required by the FDC board. The basic 4MHz oscillator is implemented with two invertors (1/3 of U25) and a quartz crystal (Y1). A 4MHz crystal oscillator and a divide by 2 and divide by 4 counter generate the clock signals required by the FDC board. The basic 4MHz oscillator is implemented with two invertors (1/3 of U25) and a quartz crystal (Y1). A 4MHz crystal oscillator and a divide by 2 and divide by 4 counter generate the clock signals required by the FDC board. The basic 4MHz oscillator is implemented with two invertors (1/3 of U25) and a quartz crystal (Y1). A 4MHz crystal oscillator and a divide by 2 and divide by 4 counter generate the clock signals required by the FDC board. The basic 4MHz oscillator is implemented with two invertors (1/3 of U25) and a quartz crystal (Y1) is the clock A 4MHz crystal oscillator and a divide by 2 and divide by 4 counter generate the clock signals required by the FDC board. The basic 4MHz oscillator is implemented with two invertors (1/3 of U25) and a quartz crystal and on page 27, 3.1.2 Y2 is your crystal for the video
I had a model 3 for a bit in the 90s
Tandy also made a sound card that you plugged into the PIO port. It was limited in that it could could play one note at a time. I manage to programed it so it would play the wedding song and a few others.
I Brought TRS-80 Model 4 as used I couldn't get it to work I had no boot disks I took it back to store And got my money back now wish I keep it
@RetroLogicLaboratory
5 жыл бұрын
Oh *sigh* that's too bad! :) Keep an eye out locally, sometimes owners just want to get rid of them and don't know that they are quite valuable now.
Always wanted one after reading Ready Player One.
that 34 pin header is in the location for the hi res card. theres a guy that still makes them his channel is RE1974 and for that extra 64 k of ram it can be used and a virtual disk drive from what ive heard.
Very well done video! Thanks for sharing! I worked at radio shack in the mid to late 80's and always wanted one a Model 4. I've been looking on eBay for a while, but can't seem to find one if working or good condition for a reasonable price.
@RetroLogicLaboratory
7 жыл бұрын
Thanks for the nice comment! I also worked at Radio Shack; from '89 - '95. I found this Model 4 on Craigslist; came with original manuals, a bunch of disks and the original sales receipt (sold by someone I knew which was kinda cool). Lots of sellers on eBay know the value of what they have.. I've found the TRS-80 gear can be pretty pricey.
This is just unbelieveable, just so amazing, I love it! Thank you for this video, I just found one of these computers in my dads room and cant figure out how to use it xD Could you do a video explaining how to use one of these?
@RetroLogicLaboratory
6 жыл бұрын
Hey sorry for the slow reply! Great idea for a video, I'll give it a try when I find my TRSDOS disks again.
Back in the 90s, someone gave me two Model 3s and a Model 4. Wish I still had one of them. I have a Model 100 laptop and a CoCo 2 now. Although all Radio Shack computers had a TRS-80 badge early on, neither is compatible with the TRS-80.
@RetroLogicLaboratory
6 жыл бұрын
Oh man, that sucks. If I kept some of the "junk" I literally threw in the garbage in the late 90's I could probably pay a mortgage payment or two with the funds I could get for them today.
@Sashazur
4 жыл бұрын
The term “TRS-80” didn’t denote compatibility. Among all the TRS-80s I think maybe only the model 1 and model 3, and some of the color computers, were compatible with eachother.
the Z80 is a great cpu.. I’m not 100% positive but i belive the model 4 could support 2 more floppy drives externally through the internal 34 pin connector…that 2x8k static ram was video memory. Hence the close proximity to the crt controller.
I will never understand why Tandy never used Ziolog support chips for the Z-80 (CTC, DMA, PIO, SIO ect). I am surprise they never made their own Logic Glue for their own boards like commodores did for their computers. It would have saved space on their "mobo'.
It seems the monitor has a rather high refresh rate, it doesn't flicker in front of your camera.
@RetroLogicLaboratory
6 жыл бұрын
Good observation. Not sure what the refresh rate is and I wasn't paying attention to what rate I filmed in when I did this video. Maybe I'll pull it apart again an try and measure it!
You probably know this, but the CoCo was originally designed as a VideoTex terminal and not a full fledged computer.
11:19 in 1986 creating any document with a dot at the end would mean anything after the dot would be the documents password.
Thanks for sharing! I always wondered what was in one of these. I have a Z80 all-in-one that was yet more expensive, and leaned a lot on the Model 3/4 for styling, but was a very different/better machine inside, the North Star Advantage. Always wondered if it was just a styling copy or whether there were engineering similarities too -- doesn't look like it though.
@RetroLogicLaboratory
7 жыл бұрын
Oh ya, the North Star Advantage is a cool looking machine. I've seen the occasional one on eBay, have been very tempted in the past to try and pick one up! That said I don't know anything about them, but that's the fun part of this hobby isn't it?
@dualityk
7 жыл бұрын
I put up a super quick five minute overview up on my channel last night, and your comprehensive video here is pretty inspiring; I'll try to put up something more comprehensive when I've got a minute, because I think it deserves more attention than it's gotten.
I didn't know the Apple II used a Z80. I thought it needed a separate Z80 board to run CP/M.
@diggydude5229
6 жыл бұрын
The Apple II used a 6502. It did need a Z80 expansion card for CP/M.
@scottlarson1548
6 жыл бұрын
Not according to this video.
@RetroLogicLaboratory
6 жыл бұрын
Doh! I'm an idiot. Not sure why I was thinking the Apple II used a Z80.
The relay is for the cassette motor control.
The rows of silver pads are a test point for testing in the factory, they never connect to anything user related.
@RetroLogicLaboratory
6 жыл бұрын
Aha! That explains it. Thanks for the info!
I bet that's a 26-1067 which would have started life as a 16K diskless Model 4. Those are the only M4s which use the M3's dual PSU arrangement.
@RetroLogicLaboratory
7 жыл бұрын
I was curious and had to check so I flipped the machine over. I can't remember if I mentioned this in my video but there is a sticker on top of the original SKU that says "Upgraded to 26-1069". So I would assume you are correct! I couldn't find the original receipt (its around here somewhere) but it would be interesting to see if it was sold as a 26-1067 and then sent back for the upgrade, or if it was shipped as an upgraded unit. As a side note, the serial number is 000751 which seems quite low. PS - love your videos!
@RE1974
7 жыл бұрын
It varied from region to region. Most people who bought the cheapy 16K M4 bought it with plans to upgrade it themselves with any of the number of aftermarket disk drive upgrade kits for sale at the time. I'd say very few people purchased 16K M4 and then got RS to upgrade it. In any case, if RS upgraded it they would not change the SKU number, it would still say 26-1067. HOWEVER, I do know instances where RS ended up with an inventory of too many of a lower spec machine (the 4K L1 M3 springs to mind) in which case they were upgraded to the new spec prior to being sold, and those got the updated SKU number. Tandy Australia found themselves with way to many 4K L1 M3s which they upgraded to 16K M3 Basic and updated the SKU from 26-1061 to 26-1062 however you can easily peel this sticker off and it ways says 26-1061 underneath. Keep up the good work and see you at Tandy Assembly in Chillichothe, OH in October.
The drive door isn't going to save those disks from the magnetic field created by the CRT and the flyback when the CRT turns on and off. I wouldn't have the disks anywhere near that magnetic-field monster.
the 6116 is a 2k x 8 static ram
I found it hard to be a "hater" for any of the chips. Z80 had it's big register set and block instructions... 6502 had it's kinda "proto-RISC" thing of not many instructions but loads of speed... I did a little bit of 6800 but, sadly missed out on the 6809.... but that would have been cool too. Oh yeah... actually.... there was one to hate: the 8080 with it's vile ugly assembly syntax which carried on into the 8086, and all the other horrible horrible x86's that we've still got today. Thanks heaven for ARM and ATmega or I'd still be stuck in the 70s wishing I had a Model 3.... a beautiful machine like the one you're taking apart... but better... because "silver!!"
That’s not quite accurate. I would frequently use a model 2 with a 8 inch floppy drive. The model 2 was nothing like the model one and was not an upgraded version. It was an entirely diffrent system. One thing you can do is hold down the reset while powering up the computer and bypass the requirement to boot from a floppy drive and boot directly into basic. If I remember correctly.
I used these in 7th grade. I hear these use composite video for the monitor display. I wonder if one could hook up a gaming console to this monitor. may have to splice in a connector. I know it's a green screen and games might not look good on it.
@diggydude5229
6 жыл бұрын
It would probably work, as the monitors were allegedly pulled from unsoid TV sets.
@RetroLogicLaboratory
6 жыл бұрын
I lived in a green-screen world back in the day. Depending on the game, some actually looked better on a green screen. I think that the Model 4 might use a 15khz monitor signal rather than composite though. Might be fun at some point to try and drive it.
Black and white, no internal sound, and still that expensive in spite of there being the fantastic Atari 8-Bit family out at the time.
@Sashazur
4 жыл бұрын
Yeah but this was aimed at a different market - business/high end. The Atari didn’t have as much storage, couldn’t display as much text, etc.
found the model 4 in the trash few day ago it powers on but just has alot of random numbers on the screen and the orange reset key is stuck down
@RetroLogicLaboratory
7 жыл бұрын
Model 4 in the trash? Crazy! Yeah random numbers on the screen sounds repairable to me. First guess would be CPU and video generator are fine, so I'd check RAM and ROM chips. I'd also check all the chips in sockets and try to reseat them. But most importantly don't give up! These are pretty valuable little machines when working.
@joseph9770
7 жыл бұрын
Lucky day! I was just day dreaming about finding one of these just laying around somewhere for free! :-)
The blue chip "RP4" means "Resistor Pack 4".
@RetroLogicLaboratory
7 жыл бұрын
Awesome, thanks for pointing that out!
I thought the Model 2 used a Motorola 68000, not a Z80 EDIT: I'm wrong, that was the Model 16
@RetroLogicLaboratory
6 жыл бұрын
Ya, the Model 1, 2, 3, 4, 12 and 16 are almost the same computer (Z-80 based). The 16 had a 68000 co-processor board so you could run Xenix. I can't remember if that was an option or standard equipment though. I think the Model 12 might also have had the option to run the 68k as well.
Ugh, the bodge wires on that board.
Didnt these have a pac man game built in?
@Sashazur
4 жыл бұрын
Nope, these didn’t have anything built in, you had to boot up the OS from a floppy. And these were marketed as serious business machines so there wouldn’t have been any games.