I'm curious about the ZX Spectrum +3 (from an Amstrad CPC user perspective)

Started by norecess, 20:10, 14 March 22

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norecess

Sorry, maybe this topic was already discussed, but I did not have the patience to go through the 23+ pages of this section of the cpcwiki forum to search :)

From what I understood about the platform, I think we can consider the ZX Spectrum +3 as the cousin of the Amstrad CPC 6128 (same thing for ZX Spectrum +2, being the cousin of the Amstrad CPC 464, right?).

From there, 2 questions:

- Are all software running on the original ZX Spectrum compatible with +3 machines ?

- The demos for ZX Spectrum (https://www.pouet.net/prodlist.php?type%5B0%5D=demo&platform%5B0%5D=ZX+Spectrum&page=1&order=thumbup) are distributed in .TAP format . I'm surprised, I would expect instead a .DSK file or something similar. Does it mean the +3 is an ignored machine, developers still preferring to target 64Kb+tape instead of 128Kb+disc?

Thanks!


BSC

From my experience as a Speccy user before I got my CPC:

Question 1: Yes, the +2 and +3 machines come with a 48k mode which is essentially a built in 48k ZX Spectrum. 

Question 2: I think one reason for that is the sheer amount of incompatible disk systems that predate the +3 while tape has always been the same on all Spectrums.

Now I am wondering where your sudden interest in that platform stems from ...  :)

norecess

@BSC

QuoteQuestion 2: I think one reason for that is the sheer amount of incompatible disk systems that predate the +3 while tape has always been the same on all Spectrums.
I don't understand. They only had 3" right? You mean that some 3" discs (brands) may work and other would not work ? or is it about the 3" drive itself, that varies over machines ? (cf. like our CRTC models in Amstrad CPCs)
I guess it's not a problem nowadays (Gotek)

QuoteNow I am wondering where your sudden interest in that platform stems from ...  :)
Ahah, nothing, really. Just curiosity and trying to understand the platform. I'm not going to invest any time/money on it as a secondary retro machine. I already have my Amiga for that :P

villain

I think it's something that they already had expansions for diskdrives (+D for example, with own DOS and many others) before the +3 hit the market. So this never became kind of a standard.

eto

Quote from: norecess on 20:41, 14 March 22I don't understand. They only had 3" right? You mean that some 3" discs (brands) may work and other would not work ? or is it about the 3" drive itself, that varies over machines ? (cf. like our CRTC models in Amstrad CPCs)
The Spectrum was launched in 1982. The Spectrum +3 came in 1987 and only 15% of the sold units were Spectrum 3". Afaik you could also not connect a 3" drive to the old models. So 3" was never the "standard" disc format on the Spectrum.

It's a bit like 5.25" on the CPC. Although many had a 5.25" drive, you will find most software on typical 3" images.

norecess

Oh I see. That's a weird state, then.. (and honestly, it sucks). Thanks for this info!

andycadley

1) Almost. In theory they were supposed to be compatible but there are a few subtle issues:

a) Amstrad changed the ROM slightly to support the additional functionality and some software makes assumptions about the values stored within (typically blocks of FFh to use as an IM2 vector table). There was software, known as The Ghost, which used the special "all RAM" mode to store a copy of the original 48K ROM which could fix some issues, but the contention arrangement when the memory is arranged like that is slightly different so it doesn't always work.

b) There are some slight timing differences which can upset multicolour effects.

c) Due to an error in some of the technical documentation, the RAM banks which are contended in the +2A/+3 models are different to those that were contended in the original 128 and +2 designs (while the original +2 was manufactured by Amstrad it used the ULA from the 128 I believe). Although this probably only affects original 128 software (and conversely some later releases like RoboCop 3 when loaded on an original 128)

2) The +3 was very late in the day and not terribly popular (certainly compared with disk based CPCs). Users typically made do with cassettes or occasionally oddities like Microdrives or Wafadrives. The Russian scene was one of the few places where disks really took off, but they mostly settled on TR-DOS which isn't compatible. The end result is that most Speccy software is tape based and even modern, high speed, loading tools are typically focused on dealing with tape images.

dragon

The +3 sound that it's not designed by the amstrad team... Probably more from a Sinclair people or any other subcontract. 

They don't follow the amstrad normal copyright design mcxx in the boards and so. All made by amstrad follow it, amstrad, pcw, pc etc.. But the Sinclair  don't.

And I think they probably made some changes to fit all they search  in the gate array. 

keith56

The +3 added the 3 inch disks of the CPC, but as others have stated there were many other disk formats existing out there, so it never gained popularity.

The +3 added a new 'CPM compatible' banks switching mode, which is the only way on the speccy to page ROM out of the &0000-&3FFF range, which would have been nice to have on the Spectrum 128

I get the feeling theres a bit of an 'anti +3 bias' from the speccy community due to the reasons that its the minority of the spectrum hardware base, and more significantly that it's made by sinclairs rival after their failure.... it's a shame as the standardized disk format (Betadisk is a nightmare!), guaranteed AY, built in joysticks and better banking options mean the +3 was a real nice system.
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dragon

That's totally cheap design by amstrad  ¿how many systems are out there that don't have a switch on/off.?.Even the nes have on/off.


And for some obscure reason the  +3 have a high failure rate in the  gate array,many are dead even in the first issue they made totally wrong ay out circuit.


Yes, is ignored by the spectrum community. The ula book ignore it and nobody have made a ula replacement..  Where all previous spectrum have it.  Probably because as the normal format was tape with a divide you can get the same  in a 128 that yo get in the +3 and more faster. 

norecess


Strident

It's worth noting that there were plenty of us Spectrum owners that had +3s back in the day and really liked them. I used my disc drive loads and even dabbled with some of the CP/M software from Amstrad CPC/PCW users.

There are lots of people in the Spectrum community that hate on the Amstrad-made +2s and +3s. But they're mostly just bitter about the fact that Sugar saved the whole Spectrum range and gave it a lifeline that kept it going for years. (You could argue that he even had to kill it off deliberately himself, as he'd done such a good job. ;) )
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chinnyhill10

Quote from: Strident on 02:12, 19 March 22There are lots of people in the Spectrum community that hate on the Amstrad-made +2s and +3s. But they're mostly just bitter about the fact that Sugar saved the whole Spectrum range and gave it a lifeline that kept it going for years.

I enjoy reminding them them that Robert Maxwell was sniffing around and that would have worked out REALLY well. They tend to shut up after that.
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kolleykibber


dragon

I have buy one recently.

It was "cheap" because was dont' tested. And it have result in a nightmare. Finally it works by some type of obscure miracle.


-It arrive without the paws (yeah the +3 have four rubber removible paws under lol).

-Ram dead.
-FDC controller dead.
-Membrane keyboard dead.
-Fdd dead.
-Ula/asic dead.(yeah thas was so funny amstrad don't spend to much money at  factory in the tin of the ula and my ula was desoldered partially).

Anyway I like it specially to play some games that don't was released in amstrad.

One curious thing i found testing games. When I play Indiana jones and the last crusade in the spectrum  I can't heard the sounds in the TV even with tv speakers at 100%, opposed to the amstrad. I was thinking oh well the ay as died too.

Then I think, OK best I want try take a look at the dissasemble code and compared it with the amstrad version.

I made a discover chilling. Something in u.s gold add a few lines of code in the spectrum version that are not present in amstrad version.

The pieze of code tell something like:

O.k so now we read the volumen for one of the three channel of the ay...

Then we  subtract  8 to the volume¿?. (the ay have a volume between 0 and 15). And then if the volumen read was 8 or less then the volumen=0=silence.

So the result of that was that the game was running the volumen between 2 and 4.  :picard2:

Make practically unable to heard.

Remove the crapp subroutine make the spectrum sound equal that amstrad version.

And I have found another game with the same problem. But I don' take  a look at it. But more strange, sound is  o.k in the menu but not Ingame.


So I was thinking if part of the problem was the programmers that made some obscure things in the spectrum. To contribute the dark leyend of the +3 disks.





chinnyhill10

Quote from: dragon on 02:43, 19 April 22The pieze of code tell something like:

O.k so now we read the volumen for one of the three channel of the ay...

Then we  subtract  8 to the volume¿?. (the ay have a volume between 0 and 15). And then if the volumen read was 8 or less then the volumen=0=silence.

So the result of that was that the game was running the volumen between 2 and 4.  :picard2:

Make practically unable to heard.


There's a load of US Gold/Tiertex games like this. UN Squadron is another.
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Shaun M. Neary

Strider also fell victim to this syndrome. Can barely hear the music on the title screen!  :laugh:
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dragon

Lol, then probably all can be patched.  :picard2:

Maybe Clark Kent  works in u.s gold as sound programmer wtf.

Thats the code of indiana jones, left amstrad right spectrum.

https://www.amazon.es/photos/share/GCWNEwa7R0gk1HVk2ToFc7frXPSU2ZKIWWuwKnA4WBF

Easy view the code= in the two plataforms except the part that down the volume. (the sub 08 and around).

Maybe there is a posibility they use the same code in all games...

Rapid look at u.n squadron it down the volume as  the indiana  try search in hex editor "cB 3a cb 3a"  and change it  to 00.

andycadley

Weird. Although a lot of +3 machines shipped with utterly broken sound, so maybe it was just a dirty hack to try and cover up the distortion you heard on those models?

dragon

¿Or maybe is to high in other spectrums?. I don't have others to test. 

ZbyniuR

Amstrad and Spectrum are not cousins. They are like bird and octopus, both have beak and need some water to life, but everything else is different.  8)
6128 and ZX+3 have one thing common, FDD with the same files system. That's true. But 464 is poor cheap CPC, more like ZX48 between Spectrums, not like ZX128/+2, which are much better than ZX48.
 
Graphic chip in Sinclair's Spectrums and grey ZX+2 have the same timings, but black ZX+2 and ZX+3 have different. Similar like different CRTC in Amstrads. If demo work on one of them, don't will be work on other. Or must be write second version of codes.

For 464 is RAM expander, you can just connect and it start work as 6128, but it is not possible for ZX48. You need soldering inside a lot wires to change it into ZX128.

For Spectrums ware least 5 different resolution of FDD before ZX+3. Each with different parameters, commands, and not compatible between them. And very few users have FDD, so there was not commercial software on floppy for Spectrums before ZX+3. And if you have FDD you still need recorder for most software. So Gotek is not so useful like something what act like fast recorder.
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