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55

It definitely does not hurt to open the case and have a look at the PCB. When opening, be especially careful with the keyboard ribbon cables - They are apparently known to become very brittle with age and tend to easily break. The main victims of age and heat are electrolytic capacitors which are known to leak or bulge and leak over time, losing their ...


38

The reason was cost, since neither the original PET nor the TRS-80 required the extra high resolution and finer dot pitch found in more expensive computer monitors. Virtually all of the computer terminals of the time paired a CRTC with a high-resolution green or amber screen to generate an 80x24 text display, as that was the early standard. This required a ...


25

The answer, as always, was cost. 'White' CRTs were cheaper because they were used in B/W TV sets. The color itself has no impact on resolution, but TV tubes didn't need to be as sharp so they could be made cheaper. So why were 'high resolution' monitors green or amber? Because these phosphors have a longer persistence so the image doesn't flicker as much, ...


22

The TRS-80 series is Z80 based, and Z80 uses, like all 8080 offspring (*1,3) a separate address space for I/O. It allows easy decoding for I/O. Thus memory address 0000h is different from I/O address 00h. On logical (program) level, access to either address space is selected by the instructions used. Memory instructions always access memory address space ...


19

Since when do kids need a reason to trashtalk? Especially with an abbreviation calling for such an interpretation? And fans of competing computers where even more eager to jump the train. The war didn't start with Amiga vs. Atari ST :) But (a bit more) serious, there was also a real reason for this name: Early Model 1 where already on itself rather ...


13

I understand that an RF modulator was used but what kind of circuitry did it use to feed the RF modulator? To start with, the TRS-80 did not use an RF modulator. It delivered composite video (*1) as it was meant to be used with its own brand monitor - which basically was an RCA TV set with the RF part removed. The TRS-80 Color Computer used an MC6847 IC ...


12

I'm not familiar with the C64, and didn't do much with the Apple ][ back in the day, but I did spend a lot of time under the hood of my TRS-80. There wasn't a lot of room for plugin accelerators in the TRS-80 Model I. I did put in a CP/M daughtercard, which remapped system memory to get ROM out of the low address space, but didn't replace the processor. ...


12

The Model 1 was a self contained computer that plugged in to, essentially, a TV set. And that was all well and good, if feature light (16K RAM, Cassette port, limited text and graphics). But it was plug and play. The original version, w/4K and Level 1 BASIC was notorious, for example, for key bounce. You could buy a simple mod to fix it, and it was remedied ...


11

I've gathered some pictures. Here is an early USA advert. Note that it is never referred to as a "Model 1" or "Model I". It's just a "TRS-80". Here is a later USA ad, after the Model II was released. Note that the price has gone down, but there is no indication that they have extended the name for the original model. The new Model II is specifically ...


11

OK, this is very dusty material in my memory, so I'm relying a bit on Google/Wikipedia here. I may be able to find some of my printed documentation, but it will take a while. The granule was the allocation unit for the filesystem. I don't remember the granule size on single-density drives, but Wikipedia says for double-density drives it was 6 sectors per ...


10

Radio Shack product names not infrequently differed from country to country, even if only subtly. This answer covers only U.S. naming. But yes, the TRS-80 Model I was sold new under that name and always used the Roman numeral. This happened only after the Model II was released, and the full name including "Model I" was not used consistently. 1979 In their ...


10

Inspired by this question, whilst visiting my parents this weekend (Jan 28th, 2018) I extracted my old TRS-80 .... and here is the result: I did open the case and give it an inspection first - and I also had a fire extinguisher on hand (just in case!) but everything went as smoothly as could be hoped. The build quality is very high - I was concerned about ...


10

Thanks to RichF's answer I looked for information specifically on booting OS-9 and found that you definitely did have to manually launch even an alternative operating system. From OS-9 Level Two Operating System page 2-2, "Booting OS-9": However, this DOS is not a filename and this is not how you load or run any other program. These are the normal ways: ...


10

I support DMK in my MSX emulator, and bear in mind that it's a bit of a confused file format. It has a bunch of design deficiencies, and was clearly tightly coupled to the program that originally implemented it. But starting with the perfectly sensible stuff: The first 16 bytes are the header, which you seem to be familiar with — write protection, geometry, ...


9

I never heard of such a thing. I never read anything in any of the magazines. I've never heard any lingering of "remember when..." that you would think would flood the internet, even in this day in age. We all know about the Microsoft monopoly, but never a word about Radio Shack. That said, I have no "proof" that this didn't happen. I'll tell you what did ...


8

The above advice is very good. I'd like to add a few general putpose work methods which will help with any other vintage electronics. My uncle and I recently looked at an old ray-tube oscilloscope he bought in the 60's, which had a faulty op-amp on the trace-auto. Start by checking the capacitors and wiring, and anything else that looks like it's suffered ...


8

I too have an old TRS-80 in the attic, and I wonder the same thing. Last time I powered up a much newer computer that had been off for a couple of years, the power supply exploded with a fizz and some smoke. Probably a large electrolytic capacitor had gone bad. Problem is, these caps need a voltage to form and maintain the insulation layer on the plates. ...


8

The main TRS-80 line (Model I, III and 4) had several third party Z-80 accelerator boards. The Archbold board could bring the Model I up to 5.3 MHz from 1.77 MHz. The Holmes Sprinter boosted the Model I up to 5.32 MHz. It came in a Model III version to boost it from 2.027 MHz to 5.07 MHz. The Model 4 had several speedup board options. Incidentally, the ...


8

Page 3 of this 1983 Radio Shack catalog shows the Data Drawer in two different sizes, "printout" which holds 14-7/8×11-inch 132-column printer paper, and "letter" which holds up to 8-1/2×14-inch legal size paper. There are also inserts for cassettes and printwheels.


7

For the Amstrad PCW, there was the Sprinter card - containing an 8MHz Z80 CPU that replaced the 4MHz original, a memory expansion, and cache RAM so that the processor wasn't restricted to the speed of motherboard memory. PCWs were largely used for word processing and DTP rather than gaming; in these applications it's useful to have more memory and a faster ...


7

ROM BASIC does not support any handling of floppies at all, but System ROM allows boot thru it's function table. Of course one could handle the disk controller 'manually' from BASIC - which is what the example does. Routines (All following values are according to TRS‑80 ROM Routines Documented) The System ROM (3000h-37FFh) only supports booting a disk. There ...


6

Don't underestimate the cost of additional RAM for display memory! The TRS-80 used seven, not eight, 1x1024 static RAM chips for its display memory. They left off the eighth chip to reduce cost. Without it, the machine was limited to uppercase-only display -- one bit per character cell to specify whether that cell displayed a character or a 3x2 graphic tile,...


6

Yes, accelerators did exist - but they were usually niche products, or handled completely differently (see below). It's more of a market-driven issue than ability to speed up. Home computers never really had a big need for speed improvement. After all, any speed up would not only break games, but also be rather expensive, as the host system wasn't really ...


6

A few points to expand on previous answers: In those days, resolution wasn't limited by phosphor, but by video bandwidth (and video memory). A standard TV had a bandwidth around 2-3 MHz, enough to support a PET or APPLE ][ - style 40x24 text display, or about 320x240 dots. The TRS-80 Model I monitor had slight modifications to the video circuitry to ...


6

The oldest (smart) hardware "dongle" I know of is from 1985 in the ZX Spectrum 48K. To curb Internet piracy and as a "collateral side effect" also having more 16KB (e.g. 64KB for the game), Mikro-Gen Ltd launched the game Shadow of the Unicorn with an external 16KB (EP)ROM board that mapped on top of the internal ROM address space. This game came with ...


6

The oldest dongle like thing I own is a ROM board for the Apple II from 1978, where the whole PCB with all chips was cast in opaque thermoseting resin. This was ment to secure the software and disencurage any duplication. But tieing Software to hardware to restict usage is much older than microcomputers. Unique identifiers for machines and/or CPUs where ...


6

Following up on @snips-n-snails. The use case for this is to organize printouts for reference. A simple example is that if someone wanted the ID of a vendor or customer, it was not untoward at the time to not look it up on the computer, but, rather, pull out a printout and look it up there. This organizes printout. You can easily envision a printout for the ...


5

I can tell you as a former Radio Shack employee, we used to call them that as well. That said, I am happy with my still functioning, very modified Mod I.


5

Most TRS80 folks today run LSDOS 6.3.x as the main OS on the Model 4. The source is published, it's hackable and it is well supported by modern hardware like the M3SE and the FreHD. TRSDOS 6 was basically the same thing rebadged. For Model III mode you need to get a copy MODELA/III and add it to a TRSDOS 1.3 or LDOS 5 diskette. It's documented in the Disk ...


5

The TRS-80 Model III is a pretty robust machine but there is one common problem -- the RIFA capacitors on the power supply. These were paper-type and very often short out producing lots of smoke though generally don't cause any damage to the machine itself. There is an excellent page devoted to that procedure: http://www.akhara.com/trs-80/psrepair/index....


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