CPC 464 Version 1 Ram Chips

[mrbee]

I have a really nice CPC 464 that's been stored so well - not a hint of corrosion or anything. I believe the issue is with the RAM according to some advice ive had, and it probably has this error back in the 80s and was just stored in a case unused since then.
Here is a picture of the error I get when turning the CPC on..
Amstrad CPC 464 won't boot to basic. glitchy screen error - retrogaming post - Imgur

The motherboard I have is this one below, the ram chips are labelled "5k 4164anp-15 84a4OD" does anyone know what available ram is compatible to replace these? I've had a search and have seen 4164 ram but the rest of the numbers and letters aren't the same and a lot of vendors either don't know or aren't replying. I am looking to get a diagnostics rom and install that instead of the 40009 chip but it'll be a pointless purchase if I have no idea what ram to replace it with.

thank you for your help

[Bryce]

The rest of the numbers aren't important. They tell you the Manufacturer, Factory, Batch, packaging type and date of production. The 4164 is all that really matters. You should easily find offers for suitable chips on ebay.

Bryce.

[mrbee]

Thanks Bryce. I have ordered some off retroleum and also a rom chip with diagrom on it for me to see what ram can be saved

[mrbee]

It's all working now! The diagnostic rom wouldnt display correctly (a glitched boot screen, some error beeps, and giant numbers on the screen displayed and that was that). Replacing all of the ram, and then reconnecting one of the old chips one by one helped me single out this one ram chip that was bad. Its working perfectly now

[eto]

The diagnostic rom wouldnt display correctly (a glitched boot screen, some error beeps, and giant numbers on the screen displayed and that was that).

That is exactly what it does if it finds RAM errors. ;-)

The thing is: if RAM is malfunctioning, the diagnostics ROM cannot use it. That means it has to run solely from ROM and cannot write to the screen. So there cannot be any "normal" output. If it detects a RAM fault it executes a clever routine that manipulates the screen colour directly so it shows these numbers. Each number corresponds to a RAM IC. If it's green, the IC works fine. It it's red, the IC is broken.

[mrbee]

I understand  I just thought it would show a diagnostic screen and not a glitchy screen with giant numbers, I thought there was something wrong at first. initially was testing it on a green monitor so I just focussed on the numbers and when connecting it to a colour tv I am also red green colourblind lol I should have used a diagnostic rom on myself at the beginning i think haha

[eto]

I just thought it would show a diagnostic screen

If RAM is not working properly, it can't show anything on screen as the screen is also located in RAM. As soon as the base RAM is working, you will also get a diagnostics screen.