CPC Parts

[eliot]

Hello,

CPC Parts is new site to provide parts and hardware for CPC Users.  
http://amstradcpc.info/parts/about.php

Hope it can be useful! 

Eliot

[steve]

This site will be excellent addition to the CPC community, now it needs to offer some electronic parts, I am looking for 64kx4 dynamic ram and sed9420 data separator, and I look forward to seeing what new hardware will be produced by others for sale on this site.

I wish it every success.

[Bryce]

Hi Eliot,
       I'm sure it's a great site, but when I click on your link I get the site for half a second then I get forwarded to a 404 page. Even if I leave the "about.php" off, I still end up on the 404. Maybe it's just my PC? Anyone else having the same issue?

Bryce.

[steve]

I have just been to the site and it appears to be working.

[TFM]

Hello,

CPC Parts is new site to provide parts and hardware for CPC Users. 
http://amstradcpc.info/parts/about.php

Hope it can be useful! 

Eliot

Fantastic site eliot! Do you know where I can get the plastic cases of CPC-Plus cartridges?

[Gryzor]

Nice effort... really! Instead of relying on eBay vendors, it'd be sweet to have an one-stop shop! A shame I just bought a few belts just yesterday!

Oh, I also saw the reset switch, which according to the description can be used as a hard-pause button. I don't think I remember reading anything about that... any info on pausing the CPC??

[eliot]

Thank you for the first comments! I'm not an hardware specialist at all but I've just created something I thought important for the real CPC users.
@ Bryce : the site seems to work everywhere... Which browser? 
@TFM: Plastic case for Plus cartridges : no idea.  
@ Gryzor : Pause button : http://www.phenixinformatique.com/modules/smartsection/item.php?itemid=90

[Bryce]

Morning Eliot,
      I just tried the site on a different PC (XP with Firefox) and everything seems to work fine (nice site by the way). Last night I had tried it on a laptop with Windows 7 / Firefox, will have to investigate what's wrong, seems to be a problem with the laptop

Bryce.

[Gryzor]

@ Gryzor : Pause button : http://www.phenixinformatique.com/modules/smartsection/item.php?itemid=90

Intriguing and very easy to do... But how does it work? Also, is it sure to not cause any problems, software-wise?

[eliot]

It freezes the activity : no mode color cycling, no more rasters, no more split-screen or other CRTC features that require synchro... So it's interesting to study how a demo or program works. But we're off-topic... 

[Gryzor]

Yeah, but still: *how* does it work? What does it do to the CPC?

[Bryce]

Morning Gryzor,
      here's a quick explanation:

The pause switch shorts the "Ready" signal to ground (which is connected to the WAIT pin of the CPU). Normally, when the CPU requests data, it expects an answer within a certain time This signal is used for external peripherals that need a little extra time to answer, by grounding this pin, the peripheral says "Hang on a minute, I'm not ready yet". A useful signal, if the hardware is too slow, or if it has a lot of calculating to do which can't be completed within the time the CPU expects. By shorting it, you're fooling the CPU into thinking that it's last requested data isn't ready to be sent yet. It has a major down-side however: The CPU doesn't refresh the memory properly while this pin is held low, so pausing for any significant time (and I'm talking milliseconds here) could cause the RAMs content to get corrupted, so I can't see this device being very useful.

Bryce.

[arnoldemu]

Morning Gryzor,
      here's a quick explanation:

The pause switch shorts the "Ready" signal to ground (which is connected to the WAIT pin of the CPU). Normally, when the CPU requests data, it expects an answer within a certain time This signal is used for external peripherals that need a little extra time to answer, by grounding this pin, the peripheral says "Hang on a minute, I'm not ready yet". A useful signal, if the hardware is too slow, or if it has a lot of calculating to do which can't be completed within the time the CPU expects. By shorting it, you're fooling the CPU into thinking that it's last requested data isn't ready to be sent yet. It has a major down-side however: The CPU doesn't refresh the memory properly while this pin is held low, so pausing for any significant time (and I'm talking milliseconds here) could cause the RAMs content to get corrupted, so I can't see this device being very useful.

Bryce.

Why did I think of HAL in 2010 when I read this?

I press the button, the screen starts to corrupt and the CPC starts singing: "Daisy Daisy give me your answer do"

[Bryce]

Oh yeah, I forgot to mention that the CPC starts singing "Daisy, Daisy" decreasing in speed and tone until it fades away. It also warns you, that "I wouldn't do that if I were you Dave" as soon as your fingers approach the pause button

Bryce.

[arnoldemu]

It has a major down-side however: The CPU doesn't refresh the memory properly while this pin is held low, so pausing for any significant time (and I'm talking milliseconds here) could cause the RAMs content to get corrupted, so I can't see this device being very useful.

Thinking about it seriously.  The CPU doesn't refresh the ram in the CPC design.

The CRTC generates addresses and the gate-array reads the data and generates the screen. At the same time the ram is also effectively refreshed.

This is why it is possible to setup the CRTC so that the ram is not refreshed correctly. This is mentioned and can happen more easily on the CPC+

[Bryce]

Yes, but external Dynamic memory devices (DKtronics etc) would use the CPU generated Refresh signal? Where I assume "Daisy, Daisy" has been saved?

Bryce.

[TFM]

Oh, I also saw the reset switch, which according to the description can be used as a hard-pause button. I don't think I remember reading anything about that... any info on pausing the CPC??

I have a small expansion card, built like despicted in Happy Computer 1987 (or so), it can smoothly slow down the CPC until it freezes, nice for some games.

Yes, but external Dynamic memory devices (DKtronics etc) would use the CPU generated Refresh signal? Where I assume "Daisy, Daisy" has been saved?

Bryce.

Like I remember RAM expansions (of external nature) must have their own refresh. At least Dobbertin was writing something about this in his handbook of the 512 kB expansion.

[Bryce]

Yes they have their own Refresh circuitry, but it reads the Refresh signal to know when it's the right time to do it. If that signal is paused, then they wont refresh.

Bryce.

[CloudStrife]

Well, we speak about CPC... Who need a RAM extension on CPC ?
(And it's depand on extension design, you can build a refreshing without using /RFSH at all...)

[Bryce]

Of course, I was just pointing out a technical detail which doesn't seem to have been mentioned anywhere else.
I also use a "bare-bones" CPC with no extra RAM.

Bryce.

[TFM]

Well, we speak about CPC... Who need a RAM extension on CPC ?

People who don't like to live in caves? 

[Gryzor]

Oh yeah, I forgot to mention that the CPC starts singing "Daisy, Daisy" decreasing in speed and tone until it fades away. It also warns you, that "I wouldn't do that if I were you Dave" as soon as your fingers approach the pause button

Bryce.

Not very clever; what if I'm not called Dave?

[Bryce]

There wasn't enough RAM free to digitise "Themistocles" So they went with Dave.

Bryce.

[CloudStrife]

 
People who don't like to live in caves? 

Yep... And we can had a external processor like a Core 2 Duo, a Sound Blaster Audigy, and a new graphic card...

[Bryce]

I'll get to work on the Sound Blaster extension right away Not sure how I'm going to get the nVidia GTX485 connected though, I may need to overclock the Z80 a little

Bryce.