Subject: Jupiter Ace

From: "Philip Pemberton" <[email-masked]>
Date: Mon Mar 17 01:37:00 2003

Hi all,
    I'm now starting on the Jupiter Ace again and I've got one really big
question that's been bugging me for a while. How the heck does the Jupiter
Ace display *graphics* on-screen? It looks like the chargen is text-only and
there's no way 256 characters can cover the entire screen. Does anyone know
how Jupiter Cantab pulled this off? My Z80 is *very* rusty - otherwise I
would have disassembled the ROM and found out myself.
    And yes, the Ace is well on its way to getting fixed. I need to rebuild
a few vias and replace some IC sockets, but it should work by the time I'm
finished with it.
    I also need a 32-ohm speaker, circular, about 1 inch in size
edge-to-edge. Has anyone got a spare for sale? These same speakers were
*apparently* used in some of the Sinclair machines (Spectrum and ZX-series
IIRC).

Thanks.
--
Phil.
[email-masked]
http://www.philpem.dsl.pipex.com/

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From: "Witchy" <[email-masked]>
Date: Mon Mar 17 17:25:14 2003

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On
> Behalf Of Philip Pemberton
> Sent: 17 March 2003 07:37
> To: [email-masked]
> Subject: Jupiter Ace
>

Can't have been from what I remember; the original Speccy used a piezo
'speaker', and later ones fed the sound output through the RF line....none
of my Sinclair machines have that sort of setup, *but* the likes of the
Oric-1, Camputers Lynx etc all did. Even the Microbees that I'm currently
looking at have that sort of speaker....not sure if it's 32ohm though.

cheers

--
adrian/witchy
www.binarydinosaurs.co.uk - the online computer museum
www.snakebiteandblack.co.uk - monthly gothic shenanigans

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From: ben franchuk <[email-masked]>
Date: Mon Mar 17 17:30:00 2003

> looking at have that sort of speaker....not sure if it's 32ohm though.

What about getting a cheap 32 ohm headphone , and use the speaker off that?
Ben.

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From: [email-masked] (Tony Duell)
Date: Mon Mar 17 18:36:38 2003

> Ace display *graphics* on-screen? It looks like the chargen is text-only and

It doesn't!. 

You've noticed the problem. All you can do is redefine the characters 
(acutally, it's worse than you think -- 1K bytes of RAM is 128 8*8 
patterns -- the high bit of the character code is used to invert all the 
dots in the pattern IIRC). And 256 chracters is not enough for the entire 
screen.

That's why you can't have an arbitrray image on the screen. There was a 
Jupiter Cantab untility to allow setting/reseting points, and one of the 
error messages was something like 'All characters used' :-)

> edge-to-edge. Has anyone got a spare for sale? These same speakers were

My obvious thought is that most cheap stereo headphones are 32 Ohm 
impdedance, and about that size. How about raiding a pair?

-tony

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From: "Philip Pemberton" <[email-masked]>
Date: Tue Mar 18 01:07:00 2003

> impdedance, and about that size. How about raiding a pair?
See my other message - I got the impedance wrong. The Ace used a 220-ohm 1"
diameter speaker... Again, unobtainium.
Farnell have got 8R and 64R speakers, but they're *huge*.

Thanks.