Found a RAM/ROM board inside my non working CPC664

[geebus]

Hi folks, I bought 2 schneider  CPC664's a while back and have only just opened up the non working one of the two after thinking there may have just been a dry solder joint somewhere (my upscaller was getting a momentary signal now and again, ctm 640 shows nothing).
After I opened it, I put the detective work to one side as I found a board plugged into the inside.
it's quite obviously a RAM/ROM board, however it looks to have space for a few other things. maybe even another bank of 64kb RAM! I'm assuming that would require the missing chips though.
I took the CPU and the ROM out of the board to see if the expansion board was the cause of the 664 not working. Sadly it wasn't, so i'll need to dig into that some more at some point.

Anyone else seen something like this before and able to tell me more about it?
I can't see any manufacturer name/model anywhere.

[Bryce]

That's a Vortex card: http://www.cpcwiki.eu/index.php/Vortex_Expansions_RAM_card

They are particularly unreliable due to all the connections and questionable mounting.

Bryce.

[geebus]

Thanks for identifying the card so quickly!
Reading on the page about it, it says that it will not fit a 664.
Do you think someone has put it in the 664 by mistake thinking it would work any way? or was another model made that worked with the 664?
OR does it mean it will not physically fit inside a 664? which it clearly did in this case.
I'm going to do some reading of the manual that is on the wiki to see if there is anything I should know about it that will help me figure out why it's in the 664.
It looks as though it originally came with a eprom and a chip below it which I do not have. I can't see what these chips are on the pictures in the Wiki, so i'll see if they are in the documentation too, if no one already has access to one.

[Bryce]

I fixed one for someone here recently, there seem to be a few of them going around. Technically it should work in a 664, just the physical connections are probably in the wrong place. From memory, the missing chips are the ROM and half the RAM.


Edit: the smaller beside the missing RAM should be a 74HCT373.


Bryce.

[geebus]

Yeah, looks like some boards were sold as 64kb expansions with the ability to add more later. Could go up to 512kb according to the documents. So the one I have is simply a 64kb expansion.
So in theory I should be able to burn a rom and put the missing logic chip in, then run it on one of my machines?
No real reason it shouldn't really. Hopefully the 664 it came out of is an easy enough repair and I can put it back in there.

I'll read more into the documents and see how to get 512kb total. I doubt it'll be a case of just putting in the correct ram chips. Would need different logic chips too wouldn't it?
I have lots of chips for upgrading 8256 boards to 512, so it's a possibility in the future to try this out.

[Bryce]

The first thing I'd do is remove the GA and CPU from the Vortex and test the 664 without the expansion to check that that's working.

Bryce.

[geebus]

Thats exactly what I done as per my original post.
Sadly, no luck.

[Bryce]

Then focus on the 664 first and get it working without the expansion before you do anything else.

Bryce.

[GUNHED]

That's a Vortex card: http://www.cpcwiki.eu/index.php/Vortex_Expansions_RAM_card

They are particularly unreliable due to all the connections and questionable mounting.

Bryce.

Have you had one? My experience is different. They work reliable for decades in all CPCs I investigated. However I usually saw them in 464.

[Bryce]

Have you had one? My experience is different. They work reliable for decades in all CPCs I investigated. However I usually saw them in 464.

They were possibly reliable back when they were new. But I've fixed quite a few of them and the pins to the CPU and GA tend to regularly lose contact and crash the machine. Probably due to age of the pins and the socket.


Bryce.

[GUNHED]

They were possibly reliable back when they were new. But I've fixed quite a few of them and the pins to the CPU and GA tend to regularly lose contact and crash the machine. Probably due to age of the pins and the socket.


Bryce.

Ah, interesting. Do they have a "common" problem. Or is it different from unit to unit?

[Ygdrazil]

A case of MeToo!
After reading this I decided to open up my own Schneider CPC 464 which i brought back home after visiting a flea market in Berlin years ago!.. And stored in a dry dark and cool place for the past decade... Back then I found the grey keys pretty exotic!

And ta da there it was , never realized there was a hidden gem inside... ROM missing and its the 512Kb version.. After tinkering around the thing seems to work!
How common was it (Germany only) back then? Not as common as the Dk'tronics I guess.. must have been a hazzle to install!
/Ygdrazil

Ah, interesting. Do they have a "common" problem. Or is it different from unit to unit?

[Bryce]

Ah, interesting. Do they have a "common" problem. Or is it different from unit to unit?

Not really. If they make the 464 unstable, it's usually a bad contact on one or more of the chip header pins (the connectors that plug into the 464 mainboard) so you have 80 pins that could possibly be causing the issue. The electronics on the Vortex board rarely fails and they were very well built too.

Bryce.

[GUNHED]

How common was it (Germany only) back then? Not as common as the Dk'tronics I guess.. must have been a hazzle to install!
/Ygdrazil

Well, instead of the dk'tronics we had the Dobbertin RAM expansions. Very nice stuff actually. Both are fully compatible and follow the Amstrad 6128 standard. The Dobbertin expansion (64KB - 512KB) was a small external box and it did run with all CPCs and Plus computers. It was definitely more common.

The big advantage of the Vortex expansion is that it allows to write BASIC programs of 250 KB (or around that size). The disadvantage is the 32 KB block banking, which makes it incompatible to common RAM expansions.


@Bryce: Thanks for the information.