CPC 464 issue

Devlin · 23:35, 13 March 14

My CPC464 is having really strange timing issues: It keeps going slow/fast at random intervals and when in games with lots of mode-switching sometimes the screen gets all glitchy.

Here's a video showing what's wrong with it using Barbarian as an example.

broken amstrad? - YouTube

pacomix · 00:55, 14 March 14

Isn't there a program that test the hardware?

Devlin · 02:47, 14 March 14

Not that I know of, and if there is, does it come on cassette?

arnoldemu · 09:52, 14 March 14

I'm guessing at a broken z80 or gate-array.

gerald · 09:58, 14 March 14

Or just the INT pin with a bad contact on either the GA or the Z80, which are both on socket ?

Gryzor · 15:12, 14 March 14

How would a b0rked Z80 or gate array cause this though?

gerald · 15:57, 14 March 14

Quote from: Gryzor on 15:12, 14 March 14
How would a b0rked Z80 or gate array cause this though?

Mode change / music / keyboard scan are usually IRQ based. If you miss some IRQ the code is waiting for, it's like a time stretch from the code point of view.
GA issue the IRQ, Z80 receive it. You may add the PPi as well for the VSYNC polling.

Gryzor · 17:51, 14 March 14

Ahhh groovy! Thanks!

Devlin · 06:25, 15 March 14

Are those easy/cheap to replace? Or should I put it up on eBay for spares/repair and buy a replacement at my earliest convenience?

Devlin · 22:27, 27 March 14

So I had a quick inspection of my Amstrad just about an hour ago, and in the process re-seated the Z80 and re-seated the heatsink on what I think was the gate array.

So far, Barbarian loaded up without issue and played perfectly for 20 minutes, had a short game, then let the music run for a while. Seemed to be completely behaving!
I'm loading up Monte Carlo Casino now, to see if there's any display glitches as i know uses a lot of mode-switching tricks, of which there were none!

EDIT:: Talk about horrible luck! My CTM644 monitor made a horrible smoke smell and the display has gone to shit. I think it's going to need re-capping.
That's pretty much cut short my amstrad gaming outside of emulators for a good long while.

arnoldemu · 10:30, 28 March 14

Quote from: Devlin on 22:27, 27 March 14
So I had a quick inspection of my Amstrad just about an hour ago, and in the process re-seated the Z80 and re-seated the heatsink on what I think was the gate array.

So far, Barbarian loaded up without issue and played perfectly for 20 minutes, had a short game, then let the music run for a while. Seemed to be completely behaving!
I'm loading up Monte Carlo Casino now, to see if there's any display glitches as i know uses a lot of mode-switching tricks, of which there were none!

EDIT:: Talk about horrible luck! My CTM644 monitor made a horrible smoke smell and the display has gone to shit. I think it's going to need re-capping.
That's pretty much cut short my amstrad gaming outside of emulators for a good long while.

that's bad, but you can use a scart cable and an external power supply.

worse if the gate-array had broken.

Devlin · 13:32, 28 March 14

Quote from: arnoldemu on 10:30, 28 March 14that's bad, but you can use a scart cable and an external power supply.

worse if the gate-array had broken.

Been looking into that, fairly cheap to sort out (roughly £25 at my estimate) but it'll have to wait until I have some proper spending money to hand since everything is going on living expenses atm.

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CPC 464 issue