Ramblings on a retro OS

[Nutterts]

Just some ramblings. So I finally have some free time on my hands. Not as much as I used too but hey... atleast I'm able to pay my bills nowdays.

So I just rebuild my little "lab" and got my Tulip Compact PC 2 from my vintage computer collection in storage boxes upstairs. It's a cute little 8086 with a dga (dual: hercules+cga) graphics card. It's in hercules mode with the original tulip monitor.

I have a nice vision of a graphical multitasking operating system. Seems like something to enjoy myself with for quite some time.

It's good to be back.

Edit: Nice sidenote, I connected a Star LC-20 which I plan on using as a debug output device.

[AMenard]

Just some ramblings. So I finally have some free time on my hands. Not as much as I used too but hey... atleast I'm able to pay my bills nowdays.

So I just rebuild my little "lab" and got my Tulip Compact PC 2 from my vintage computer collection in storage boxes upstairs. It's a cute little 8086 with a dga (dual: hercules+cga) graphics card. It's in hercules mode with the original tulip monitor.

I have a nice vision of a graphical multitasking operating system. Seems like something to enjoy myself with for quite some time.

It's good to be back.

Edit: Nice sidenote, I connected a Star LC-20 which I plan on using as a debug output device.

Nice project!

I am myself in the planing stage of building my own homebrew MC680xx computer with the intent of writing my own OS on it. I love retro hardware

[Nutterts]

Nice project!

I am myself in the planing stage of building my own homebrew MC680xx computer with the intent of writing my own OS on it. I love retro hardware

I love that plan. I don't have the time anymore but one of my idea's was to use a modern (still orderable from mouser) z80 equilivant and build a system and OS around it. I love retro hardware too. My plan is a 16bit VM to make porting what I write for this system easier. So maybe that will still happen one day.

I attached an image of my resurrected 'lab'.

[AMenard]

I love that plan. I don't have the time anymore but one of my idea's was to use a modern (still orderable from mouser) z80 equilivant and build a system and OS around it. I love retro hardware too. My plan is a 16bit VM to make porting what I write for this system easier. So maybe that will still happen one day.

I attached an image of my resurrected 'lab'.

I presently use the Amiga Forever emulator to emulate an A2000 to code in MC68000 assembler and C. I'm planning to have the low level stuff of my OS to load from eeprom and the rest form some form of more easilly upgradable media.

[Sik]

How much memory does that machine have? If you intend to make a multitasking system that's going to be a big problem to take into consideration.

[NunoLava1998]

How much memory does that machine have? If you intend to make a multitasking system that's going to be a big problem to take into consideration.

20MB or 40MB depending on the model. Though, that means you have enough memory for a multitasking system but the machine doesn't seem to be 32 bit. So you'll have to use something like MS-DOS or MikeOS.

[Nutterts]

How much memory does that machine have? If you intend to make a multitasking system that's going to be a big problem to take into consideration.

20MB or 40MB depending on the model. Though, that means you have enough memory for a multitasking system but the machine doesn't seem to be 32 bit. So you'll have to use something like MS-DOS or MikeOS.

An XT has at most 640KB of memory. The addressing space is 1MB, everything above 640KB is used for the bios, option roms etc. The only way to have more memory is to use bank switching. Using an ems expansion card like the Intel AboveBoard or building a homebrew equivalent.

Your probally thinking of AT systems like a 286 that could have up to 16MB of memory. This is quite a bit older than that.

Who told you multitasking is only possible on a 386+? That person needs to be slapped around a bit for being silly. There have been graphical multitasking operating systems written for 8bit processors. Even single task operating systems like DOS allowed the creation of TSRs to create background applications on 8088 processors.

In what way would I need DOS or MikeOS?

[iansjack]

I'd guess it is the common error of confusing RAM and disk space. It can happen when you Google something that you know nothing about.

[Sik]

Yeah, I searched it later and indeed it says 20/40MB, but that looks to be hard disk. Some random post seemed to say 640KB of RAM though I'm not 100% sure. Better than the 64KB of the original PC =P Also apparently the CPU is actually a NEC V20, which has the instruction set of a 80186, not 8088/6 (this matters since there are a handful more instructions available).

[Nutterts]

Some random post seemed to say 640KB of RAM though I'm not 100% sure.

It's 640kb

Also apparently the CPU is actually a NEC V20

It is! I accually didn't know until I properly cleaned it (and added a 8087) but didn't bother to correct. Good job on researching it.

Your question: If a system has enough memory for multitasking basicly comes down this. The amount of programs that it can run at the same time is only limited to the amount of memory you have left after your OS loads and the speed penality your willing to take for using bank switching or disk i/o to run more.

It can happen when you Google something that you know nothing about.

Imho, it only happens if you Google something thinking you already know everything. The worst mindset to have.

Let this be a lesson for young players.... Think after you Google!

[Sik]

Your question: If a system has enough memory for multitasking basicly comes down this. The amount of programs that it can run at the same time is only limited to the amount of memory you have left after your OS loads and the speed penality your willing to take for using bank switching or disk i/o to run more.

Yeah I know, but being an early computer I wouldn't have been surprised if it had much less RAM - in which case multitasking starts becoming an issue. Even if your programs are tiny don't forget you need to keep the user data in memory as well, and you're going to have a much harder time making this take up little space. (saying this as somebody who wondered how to get this to work with just 64KB RAM... ended up deciding for single tasking instead)

Early Windows versions could run with 640KB though, so it's certainly doable.

[Nutterts]

Saying this as somebody who wondered how to get this to work with just 64KB RAM... ended up deciding for single tasking instead.

Multitasking with only 64KB is not the problem, I think the problem is that you want it to do more than a 64KB system like that could.

Which system was it? If that was what limited you I wouldn't mind seeing if you could add some more memory.

[Schol-R-LEA]

Keep in mind that there were multitasking OSes for the PDP-1, PDP-8, Linc, and Altair 8800, none of which were usually loaded with more than 16KB (and often had far less). I specifically recall reading (n an collection of early Dr. Dobb's Journal issues, this particular one from around 1977) about a 6800-based timesharing OS called CHAOS which was developed by high school students for their school, somewhere in Michigan I think but I'm not sure. I don't know how much memory it had, but given the prices at the time, I doubt it was more than 32KB at most.

I seem to recall one from around that time which ran on 48KB Apple ][s, as well, but I may be confused.

I'd also mention OS-9 (a desktop/RT operating system originally for the 6809, nothing to do with Mac System 9) on the CoCo, which ran in a decadent 64KB.

[AMenard]

One of my friend and co-worker is still running OS/9 on his venerable CoCo3 with a whooping 128k!

But seriously, people are forgetting the more popular graphical multitasking OS that ran in less than a Meg of ram, Amiga Intuition (Workbench), the first mass distributed graphical multi-tasking OS and the basic Amiga 1000 came with 256k, though most people bought the front 256k ram expansion for a "Yuuuuge" 512k of ram.

[Solar]

To be fair, the Amiga 1000 had a 256kB ROM to go with that (Kickstart), but it was still pretty darn impressive. And, as opposed to contemporary Windows, actually multitasking.