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Le 26/10/2015 20:05, Orchid Win7 v1 a écrit :
> 
> (Wait, you can *print* from a Spectrum? I never knew that!)

Yes, there was a thermal printer (for thermal paper) to connect on the
expansion bus.

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On 26/10/2015 07:19 PM, Le_Forgeron wrote:
> Le 26/10/2015 20:05, Orchid Win7 v1 a écrit :
>> (Wait, you can *print* from a Spectrum? I never knew that!)
>
> Yes, there was a thermal printer (for thermal paper) to connect on the
> expansion bus.

Huh. I did not know that. Come to mention it, I don't remember there 
being an expansion port!

Ah, the hours I wasted with our Spectrum hooked up to a portable 4" CRT 
monitor. Do you know what 8x8 characters look like on a 4" screen with 
manually-tuned RF? I do...

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Le 26/10/2015 20:24, Orchid Win7 v1 a écrit :
> On 26/10/2015 07:19 PM, Le_Forgeron wrote:
>> Le 26/10/2015 20:05, Orchid Win7 v1 a écrit :
>>> (Wait, you can *print* from a Spectrum? I never knew that!)
>> 
>> Yes, there was a thermal printer (for thermal paper) to connect
>> on the expansion bus.
> 
> Huh. I did not know that. Come to mention it, I don't remember
> there being an expansion port!

You remember the pcb at the back, that is the expansion bus... At
least for the original 16k and 48k model. I do not remember if there
was a default plug/cache on it or if it was all time open.

The 128k wasted all: the keyboard and rear was different. (and the
128k were via bank switching of 16k... otherwise, it was like a 32k +
16k switched... and the double size rom (16k x 2) was also switched.
Well, it's only a 16 bits Z80, what did you expect !

> 
> Ah, the hours I wasted with our Spectrum hooked up to a portable 4"
> CRT monitor. Do you know what 8x8 characters look like on a 4"
> screen with manually-tuned RF? I do...

Mine was hooked on TV. oh the battles vs the TV shows.
Only 2 colours per 8x8 pixels was the main drawback of the display.
(and the fancy flash mode bit... hardly documented, surprising to use)
That, and only 8 colours.
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On 10/26/2015 9:06 PM, Le_Forgeron wrote:
> That, and only 8 colours.

Colours! and eight of them?
The first games I played the output was a printer.


-- 

Regards
     Stephen

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On Mon, 26 Oct 2015 19:01:28 +0000, Orchid Win7 v1 wrote:

> On 26/10/2015 06:27 PM, Jim Henderson wrote:
>> On Mon, 26 Oct 2015 18:12:33 +0000, Orchid Win7 v1 wrote:
>>> 1. Why would anybody want this?
>>
>> Nostalga.
> 
> OK, I get nostalga. I am currently sitting next to an Amiga 1200. But at
> this price?! Jesus, you could surely buy a *real* Spectrum for less
> money!
> 
> (Now I'm curious to know what the original retail price was...)

https://en.wikipedia.org/wiki/ZX_Spectrum

Lists some original retail price.  Don't thank me, thank Google. ;)

>> Or as a teaching tool - earlier computer systems were far less complex
>> than modern ones, so starting a student off with a simpler system can
>> make learning much easier, depending on the goals of the instruction.
> 
> Isn't that what the Raspberry Pi was supposed to do?

Depends a lot on what you want to teach.

> Don't get me wrong, I think it's *way* easier to learn system-level
> programming on obsolete hardware. (It's how *I* did it!) But I doubt
> many kids these days would get out of bed to see some blocky 8-bit
> graphics.

Also depends on what you want to teach.

> Which is why they invented the Pi, with it's full-HD video and audio
> capabilities and 3D rendering support... Which thus makes it impossible
> to do system-level programming, kinda negating the point.

You certainly can do system-level programming on the RPi.  How do you 
think you get a kernel developed to run on it? ;)

> And besides, for £0 you can probably just *download* a Spectrum emulator
> onto your PC or indeed phone or tablet... You don't actually need a
> physical box. (I don't know, but I'd be surprised if this thing actually
> contains a Z80. I bet it's really just a smartphone SoC running an
> emulator!)

Not the same, and as I said, it depends on what you want to teach.

Jim
-- 
"I learned long ago, never to wrestle with a pig. You get dirty, and 
besides, the pig likes it." - George Bernard Shaw

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>> (Now I'm curious to know what the original retail price was...)
>
> https://en.wikipedia.org/wiki/ZX_Spectrum
>
> Lists some original retail price.  Don't thank me, thank Google. ;)

Hmm. So, at £99, this recreation is *almost* the same price as the 
original, 30+ years later. Nice.

>> Isn't that what the Raspberry Pi was supposed to do?
>
> Depends a lot on what you want to teach.

I guess the Pi by itself doesn't do a lot; it's great for building crazy 
robots, if *electronics* is what you're trying to teach. But you need 
more components to make a usable computer out of it. And then there's so 
many other bits plugged in, you lose sight of the fact that the little 
circuit board in the middle is the part that's actually "doing" stuff.

>> Don't get me wrong, I think it's *way* easier to learn system-level
>> programming on obsolete hardware. (It's how *I* did it!) But I doubt
>> many kids these days would get out of bed to see some blocky 8-bit
>> graphics.
>
> Also depends on what you want to teach.

When I was a kid, 8-bit graphics were all you could ask for. I can 
actually recall spending *multiple hours* playing Space Invaders. I 
can't imagine why; today it seems like the most boring game imaginable! 
It wouldn't hold my attention for ten seconds. And that's kinda my 
point; kids these days have smartphones in their pockets. Why would they 
bother with this obsolete thing? (Unless you manage to convince them 
that its arcane-ness makes it "special" rather than just dumb.)

>> Which is why they invented the Pi, with it's full-HD video and audio
>> capabilities and 3D rendering support... Which thus makes it impossible
>> to do system-level programming, kinda negating the point.
>
> You certainly can do system-level programming on the RPi.  How do you
> think you get a kernel developed to run on it? ;)

You're aware that to this day, the OS includes a closed-source binary 
blob that only people who sign an NDA are allowed to look inside, right? 
Literally, you cannot operate the GPU without signing an NDA or using 
closed-source code. And since this is a mobile phone SoC, the GPU 
controls the CPU, not the other way around...

But sure, once you've started the CPU, you can do system-level 
programming. Good luck getting anything interesting done; it's not like 
you can just poke 53280 to change the overscan colour... ;-)

>> And besides, for £0 you can probably just *download* a Spectrum emulator
>> onto your PC or indeed phone or tablet... You don't actually need a
>> physical box.
>
> Not the same, and as I said, it depends on what you want to teach.

I will admit, particularly for a younger audience, there's a certain 
something to having it be a hardware box.

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>> Huh. I did not know that. Come to mention it, I don't remember
>> there being an expansion port!
>
> You remember the pcb at the back, that is the expansion bus... At
> least for the original 16k and 48k model. I do not remember if there
> was a default plug/cache on it or if it was all time open.

Huh. I forgot about that. Yeah, I think we had the 16K model. Not 100% 
sure...

> The 128k wasted all: the keyboard and rear was different. (and the
> 128k were via bank switching of 16k... otherwise, it was like a 32k +
> 16k switched... and the double size rom (16k x 2) was also switched.
> Well, it's only a 16 bits Z80, what did you expect !

So there *was* a system with bank-switching! I'm so glad I invented that 
idea when I was only 11 years old... I *knew* somebody must have thought 
of it before!

>> Ah, the hours I wasted with our Spectrum hooked up to a portable 4"
>> CRT monitor. Do you know what 8x8 characters look like on a 4"
>> screen with manually-tuned RF? I do...
>
> Mine was hooked on TV. oh the battles vs the TV shows.
> Only 2 colours per 8x8 pixels was the main drawback of the display.
> (and the fancy flash mode bit... hardly documented, surprising to use)
> That, and only 8 colours.

Oh yeah, this was a TV too. A portable TV for camping. Which, if you 
know anything about CRT, "portable" doesn't really come into it. The TV 
was 4" at the front, but about 9" long to accommodate the huge tube and 
transformer at the back. Bloody heavy too! And with manual tuning, for 
some reason... I'm guessing it was cheap?

For those that don't know, mis-tuned RF signals result in a weird kind 
of zig-zag ghosting pattern that's very distracting...

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On 26/10/2015 09:06 PM, Le_Forgeron wrote:
> Only 2 colours per 8x8 pixels was the main drawback of the display.

Oh yeah... I forgot about that! One time I wrote a program to draw 
randomly positioned circles in random colours. After a few minutes of 
drawing, most of the pixels were in the "on" state, but there were weird 
squares of colour that changed every time a new circle was started.

I also remember saving several test patterns to tape, and eventually 
discovering which colour provoked which tone from the speaker... Jesus, 
I was bored as a child!

I've always wanted to know... why is the framebuffer arranged so 
weirdly? Like, as you load a picture file, rather than filling from top 
to bottom, it seems to fill every Nth line...

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On Mon, 26 Oct 2015 22:38:03 +0000, Orchid Win7 v1 wrote:

>> Depends a lot on what you want to teach.
> 
> I guess the Pi by itself doesn't do a lot; it's great for building crazy
> robots, if *electronics* is what you're trying to teach. But you need
> more components to make a usable computer out of it. And then there's so
> many other bits plugged in, you lose sight of the fact that the little
> circuit board in the middle is the part that's actually "doing" stuff.

I've got OpenELEC running on one; it makes a reasonable media server.

Nothing else really plugged in, either.  HDMI, external hard drive, 
power.  Wireless keyboard/mouse combo that I generally don't use.

>>> Don't get me wrong, I think it's *way* easier to learn system-level
>>> programming on obsolete hardware. (It's how *I* did it!) But I doubt
>>> many kids these days would get out of bed to see some blocky 8-bit
>>> graphics.
>>
>> Also depends on what you want to teach.
> 
> When I was a kid, 8-bit graphics were all you could ask for. I can
> actually recall spending *multiple hours* playing Space Invaders. I
> can't imagine why; today it seems like the most boring game imaginable!
> It wouldn't hold my attention for ten seconds. And that's kinda my
> point; kids these days have smartphones in their pockets. Why would they
> bother with this obsolete thing? (Unless you manage to convince them
> that its arcane-ness makes it "special" rather than just dumb.)

Lower end equipment can help kids and students understand where the 
technology comes from and how it developed over time.  Understanding the 
past is useful to seeing ways in which things can be done in the future.

>>> Which is why they invented the Pi, with it's full-HD video and audio
>>> capabilities and 3D rendering support... Which thus makes it
>>> impossible to do system-level programming, kinda negating the point.
>>
>> You certainly can do system-level programming on the RPi.  How do you
>> think you get a kernel developed to run on it? ;)
> 
> You're aware that to this day, the OS includes a closed-source binary
> blob that only people who sign an NDA are allowed to look inside, right?
> Literally, you cannot operate the GPU without signing an NDA or using
> closed-source code. And since this is a mobile phone SoC, the GPU
> controls the CPU, not the other way around...

Yes, but that's true on a lot of PCs that run Linux as well.  That 
doesn't mean you can't do system-level programming on it.

> But sure, once you've started the CPU, you can do system-level
> programming. Good luck getting anything interesting done; it's not like
> you can just poke 53280 to change the overscan colour... ;-)

I think there's a lot you can do that's interesting without any video at 
all.

>>> And besides, for £0 you can probably just *download* a Spectrum
>>> emulator onto your PC or indeed phone or tablet... You don't actually
>>> need a physical box.
>>
>> Not the same, and as I said, it depends on what you want to teach.
> 
> I will admit, particularly for a younger audience, there's a certain
> something to having it be a hardware box.

Absolutely.

Jim



-- 
"I learned long ago, never to wrestle with a pig. You get dirty, and 
besides, the pig likes it." - George Bernard Shaw

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Le 26/10/2015 23:43, Orchid Win7 v1 a écrit :
> I've always wanted to know... why is the framebuffer arranged so
> weirdly? Like, as you load a picture file, rather than filling from top
> to bottom, it seems to fill every Nth line...

Probably because Pal is an interleaved image: there is odd and even 
frames. It was probably easier for the electronic in charge of 
generating the lines in that order instead of obvious linear order.

IIRC the memory was not a dual access memory (that's expensive), so for 
the chip to generate the signal, it might have been easier to read 
consecutive address (an hardware counter is cheap).

Oh, it was a time in which accessing memory was easy: presents an 
address on the address bus, read the data on the data bus. No column & 
no row selection, no wasted cycles to wait for the data (no CAS Latency !)

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