Ramblings on a retro OS

[AMenard]

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.

The A1000 didn't have kickstart in rom. You had to boot it up from a floppy disk. The A500 and A2000 were the first model with KS roms.

[iansjack]

Let's not forget the first pre-emptive multitasking OS on a personal computer - QDOS. And I believe that the QL only had a 32 KB (or was it 48) ROM. A truly innovative operating system. Notably, both these computers used the 68000 processor family (and the 6809 - of OS-9 fame - counts as an "honorary" 68000 in my book). One of the finest processors of the early days.

[Schol-R-LEA]

Huh, I assumed you'd typoed and meant 6800 instead of 68000, but I checked and the QL did indeed use the 68K.

The 6809 was in the 6800 family, and was an 8-bit CPU, but was closer to a 16-bit system in several ways. Still, I suppose that the use it is put to is the really key factor.

Motorola didn't have a true 16-bit processor, at least not one that was used in any home computers I know of. With the 68k, Motorola decided to leapfrog past 16-bit to 32-bit, but needed to be able to interface with existing 16-bit hardware, so they used a 16-bit pin-out; they even had an 8-bit version, the 68008, because they'd underestimated the time it would take for the rest of the industry to go to 16-bit. Their estimates hadn't taken into account the growing base of home computer users, because, well, none of the chip makers (except MOS Technology, perhaps) thought that home computers would be anything more than a brief fad and expected (correctly, but not as much as they thought) that their core business would be in embedded microcontrollers.

The 6800 drew heavily on the design of the PDP-11, so when the time came to design the 68K, they followed the same path from the 6800 that Digital had going from the PDP-11 to the VAX: a similar design but expanded in every direction, and what at the time was large set of general registers for a microprocessor (eight, with no fixed accumulator or index registers; there were also eight address registers, two stack registers, a status register, and the IP). The instruction set was also vastly enriched, though nowhere near the extent that the VAX's was.

Intel had the same plan even earlier (and made the same underestimate that Motorola had), but for logistical reasons slapped together the 8086 (a 16-bit extended version of the 8080A - they couldn't quite make it source compatible, but by using segmented memory they made it easy to adapt 8080 and Z80 code to it so long as the coder used what would later be called 'tiny model') as a stopgap while they put the finishing touches on the i432.

Problem is, the i432 was far too ambitious for the chip manufacturing techniques of the late 1970s - a super-CISC design meant to have hardware support for abstract data types (or OOP, depending on who you ask, not that most people see a difference these days), capability-based addressing, value-return parameter passing, and garbage collection. When it was clear that a) most of the peripheral hardware around was still 8-bit, leading to sluggish sales for the 8086, and b) the i432 project was running out of control, they added the 8088 to squeeze what they assumed would be an extra year or two out of the 8086, hoping that the problems Motorola, Zilog, and National Semiconductor were having with their 32-bit designs would give them a chance to finish the i432 before they got theirs out. Oh, the irony.

[iansjack]

The QL actually used the 68008. The Amiga used the 68000, except in later, more advanced models. Many of us spent vast amounts of cash on a 68020 or 68030 card which greatly improved performance. Oh for a return to the simplicity and elegance of that processor! I really must dig out my QL and Amiga one day. Even though there are near perfect emulators, somehow it's not quite the same as the real thing. I also still have, somewhere, a Dragon 32, the UK equivalent of the CoCo.

[AMenard]

The QL actually used the 68008. The Amiga used the 68000, except in later, more advanced models. Many of us spent vast amounts of cash on a 68020 or 68030 card which greatly improved performance. Oh for a return to the simplicity and elegance of that processor! I really must dig out my QL and Amiga one day. Even though there are near perfect emulators, somehow it's not quite the same as the real thing. I also still have, somewhere, a Dragon 32, the UK equivalent of the CoCo.

We didn't get the Sinclair computers here in Canada except for the rebranded Timex ZX-81 so my knowledge of them is quite limited. You also had a love for the Z80 in your 8bit home computer while in North America we were mostly getting 6502 based machine except for the TRS-80 and CoCo lines. Don't forget the venerable TI-99 4/A from Texas Instrument who did use a 16bit CPU in the 8bit era.

I love the M68k family too. I learn assembler at the university on small M68K based PIC board. I still own two A1000 and wouldn't mind buying an A2000 or A2500 and use it as my dev machine because my A1000 are really too limited without ram expansion and HDD. Of course my ultimate unicorn is the A4000 but they're quite rare in north america. I'll see if I can import an A1200 one day to have at least one AGA machine.

[Nutterts]

This forum always makes me feel so young when I hear some of the systems people have actually used. Especially the PDP's. I only have a very faint memory of one at my school that was only there because the teacher never wanted to trow it away. I don't know which model, but it was a quite a stack of equipment were you manually entered code in octal using switches. I was only allowed to watch, not touch. The first system these hands touched was a Philips P2000T, the first one I owned was a BBC Micro.

On the subject of memory. An idea I'm playing with is putting all memory chips in sockets so they're easier to work with and then removing almost everything. If possible only leaving 64kB. Then designing a extension card to backfill that memory like those old AST ems cards could. The reasoning behind is to be able to do a nearly instant context switch. I have the skills but it's just a scribble on the drawing table at the moment.

But it's a nice little system. Easy to work with. Easy to customize.
But especially that green phosphor glow makes me all warm and fuzzy inside.

[AMenard]

This forum always makes me feel so young when I hear some of the systems people have actually used. Especially the PDP's. I only have a very faint memory of one at my school that was only there because the teacher never wanted to trow it away. I don't know which model, but it was a quite a stack of equipment were you manually entered code in octal using switches. I was only allowed to watch, not touch. The first system these hands touched was a Philips P2000T, the first one I owned was a BBC Micro.

On the subject of memory. An idea I'm playing with is putting all memory chips in sockets so they're easier to work with and then removing almost everything. If possible only leaving 64kB. Then designing a extension card to backfill that memory like those old AST ems cards could. The reasoning behind is to be able to do a nearly instant context switch. I have the skills but it's just a scribble on the drawing table at the moment.

But it's a nice little system. Easy to work with. Easy to customize.
But especially that green phosphor glow makes me all warm and fuzzy inside.

Sourcing low value (in k) ram chips is hard to do these days. Most of the homebrew computer that I see on the web or on youtube use a single 512k ram chip.

[Schol-R-LEA]

This forum always makes me feel so young when I hear some of the systems people have actually used.

Want to feel older? Consider that it is very likely that a majority of the members have never used anything earlier than either a Pentium III or a G4, have never seen an 8-bit desktop computer except in photographs, and have never used or seen code in a version of Basic that required line numbering for every line as labels for gotos.

(For the record, the last time I tried to use one was when my boss at the Berkeley Used Computer Store asked me to update his custom labeling software in 1995, which he'd written fifteen years earlier in Applesoft BASIC. I wasted a week on that before deciding it was a futile activity and asking him if I could do it on a PC instead. He refused, for raisins, and I found out in a later project that he, a former FORTRAN programmer, couldn't understand what while loops were for or why you wouldn't just use a goto instead. Sigh).

And, if Nanolarva and some of the others are to be believed, there are probably a number who have never used anything that wasn't 64-bit, and don't remember a time when Macintosh wasn't an Intel system.

[iansjack]

... and probably more who have never used a PDP 8, or a System 38. In fact, probably don't know that such things existed.

Not to mention those who think that all computers use ASCII or have word sizes that are powers of 2.

[Nutterts]

Sourcing low value (in k) ram chips is hard to do these days. Most of the homebrew computer that I see on the web or on youtube use a single 512k ram chip.

When designing an 8bit ISA card in 2016, you use 2016 part. It'll probably use some classic 7400 series logic (they still make those) because I like the look and it doesn't require that much parts to do. But when it comes to memory I can't imagine using anything other then a modern smd sram chip, or two... or three.

Want to feel older?

No thank you! I regularly have interns at work to coach. They do enjoy me talking about the 'Good ol days' and sometimes taking something from my collection for little 'show and tell'. But it already makes me feel older then I am.

or have word sizes that are powers of 2

When it comes to manually entering code with switches. Doing it three bits at a time still has this unique sense of beauty that I don't get when looking at the same thing being done a nibble or byte at a time.

[Schol-R-LEA]

... and probably more who have never used a PDP 8, or a System 38. In fact, probably don't know that such things existed.

Not to mention those who think that all computers use ASCII or have word sizes that are powers of 2.

To be fair, I never used a 12, 18, or 36 bit system myself; I didn't start using computers until 1981, by which time the PDP-10 was already slated to stop production (System Concepts bought the rights to the design and tried to revive it with the Foonly, but collectively caught Babbage Syndrome and wasted their venture capital on endlessly improving things that were fine already rather than selling any of them), Seymour Cray's designs went from 60-bits to 64-bits after he left Cyber in 1972, and pretty much everyone else had gone to 8-bit bytes by the early 1970s, too (primarily out of follow-the-leader after Big Blue made the switch in 1966, rather than for any technical advantages). I don't know of any significant computers made after 1960 that didn't use either 6 or 8 bits as its byte (6 was the size of the Baudot code, which was the primary predecessor to 7-bit ASCII), though several before then used decimal bytes and BCD arithmetic, usually in systems meant for "business computing".

The first computer I ever programmed on was PR1ME 400, which was a 16-bit mini timesharing system that my high school allowed open access to because it was the last year it was to be open and there were only the freshman and senior classes being held there - when I went to a different school for sophomore year, they had a closed computer lab, sadly. I mostly used an Apple ][+ and an IBM PC/XT through the 1980s, though neither of them were my own (the Apple was shared with my younger brother, while the PC was for my father's office so I only got to use it at night). I was on several local BBSes, some of which were FidoNet nodes, but my first experience with the Internet wasn't until Fall 1992. I got into a lot of trouble with the college I was going to (Southern CT State U., the second time I was there, having taken three years off after Spring 1989 for financial reasons, during which time I learned PC hardware assembling at a PC store I worked for) because I was spending more time on USENET than on my classwork. When the September That Never Ended began a year later, I was already a grizzled veteran complaining about the newbies.

[AMenard]

Well, my first computer was the trs-80 mc10, followed by the coco2, c64, atari 800xl (those 3 at the same time), then I moved to the atari st, amiga 1000 and then PC XT and up from there. I got that trs-80 mc10 when I was about 17, I'm 51 now. I wasn't in IT back then, I was an arc welder at a ship yard. I had an accident at work and had to retrain for something else when I was 26 so I went back to college to learn programming which at the time was done with Pascal, Cobol and Rally on a Vax. My first job after college was for a division of IBM where I converted JCL to Rexx for their mainframe based banking system.

I don't consider myself "old", I prefer to think of myself as a well "aged" wine...

[MichaelFarthing]

... and probably more who have never used a PDP 8, or a System 38. In fact, probably don't know that such things existed.

Not to mention those who think that all computers use ASCII or have word sizes that are powers of 2.

It occurred to me reading this that all human beings are computers based round what might be seen as a 6 bit architecture - though more accurately we are a base 4 machine with each 'word' having three base-four 'bits' where a bit can take one of the values:

enum (
c
g
a
t
)

(though I shall probably be pulled up for using an 'enum' since the ordering is not really relevant)

[Schol-R-LEA]

(though I shall probably be pulled up for using an 'enum' since the ordering is not really relevant)

OK, I deserved that.

[NunoLava1998]

This forum always makes me feel so young when I hear some of the systems people have actually used.

Want to feel older? Consider that it is very likely that a majority of the members have never used anything earlier than either a Pentium III or a G4, have never seen an 8-bit desktop computer except in photographs, and have never used or seen code in a version of Basic that required line numbering for every line as labels for gotos.

(For the record, the last time I tried to use one was when my boss at the Berkeley Used Computer Store asked me to update his custom labeling software in 1995, which he'd written fifteen years earlier in Applesoft BASIC. I wasted a week on that before deciding it was a futile activity and asking him if I could do it on a PC instead. He refused, for raisins, and I found out in a later project that he, a former FORTRAN programmer, couldn't understand what while loops were for or why you wouldn't just use a goto instead. Sigh).

And, if NunoLava1998 (what do you mean by "nanolarva", lol) and some of the others are to be believed, there are probably a number who have never used anything that wasn't 64-bit, and don't remember a time when Macintosh wasn't an Intel system.

I actually at the age of 3 used a computer that was 32bit. And i've used home PC's that are 32bit. But the computers i use for my work are 64bit.