How to create replacement ROM for CPC and Plus?

Started by eto, 10:34, 10 February 22

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eto

So, I have never done this and I couldn't find condensed information what is really needed to create ROMs for the CPC and the Plus cartridges - not too expensive of course ;-)

What Eprom/Eeprom types can be used in the CPC/Plus? What programmer do I need? What would you recommend to erase Eproms? Are there any other chips besides Eprom/Eeprom that could be used?

Where would you recommend to buy Eproms? The typical Eprom models are often out of stock or very expensive - or in used condition from Ebay. Eeproms also seem to be an alternative but are even more expensive.


Maybe someone who dived into that can share his/her wisdom.

Nworc

Hi.

I personally find the 27C128 type eproms (128kbit = 16KB) with the nice glass bulb fits best to the 80's design the CPC models are. I can speak only for the non-plus CPCs.

This is the right choice also electrically. Eproms that I have burned or that have been burned decades ago are still in working condition and haven't lost one bit  :)

These are widely available on that infamous internet auction site for approx 3 Euro per piece.





Kris

on Plus, I use 27C1001 & 4001 , depending on size you need.


eto

What would be a recommended Eprom programmer? And what's a recommended tool to erase them?

Nworc

The Eprom programmer is the expensive part of the fun. I have an old Batronix Galep, the software is quite good. The company still exists and they are still doing the programmer, but I guess you don't want to pay 500 euros just for the little fun to burn something. I hope someone else comes up with a recommendation - otherwise you can check the internet auctions from time to time to look for a used one, or try one of the cheaper chinese copies. Buying chinese material means that you know how to repair and improve stuff, as this is the first thing you do when it arrives. If you can do that, you can save some money, and I still have a lot of fun with the chinese desoldering station from Zhongdi, it goes suck suck suck and there it goes, a fearsome beast with 44 legs. Okay, I lost the track a little.

Erasing: buying an eraser is the best thing you can do, as UVC light makes you blind. If you don't fear that, you can build a box with a switch that turns off the lamp when you open it, and be using a Philips TUV 4W/G4 T5 lamp inside. This lamp is normally used to clean the water for e.g. aquariums, but is perfect for this job. But building that box is more expensive than buying one, so forget it. In that internet auction site look for Eprom UV Timer, the one with the aluminum body is a good one.

Welcome to the club. Let's burn!

Richard_Lloyd

Here's the Chinese programmer I use. It has a huge list of chips that can be programmed and the software is updated regularly. Check eBay for prices.
Richard
CPC464, CPC6128, PCW8512, PCW10, BSA & NSP

Bryce

Quote from: Nworc on 23:12, 10 February 22
The Eprom programmer is the expensive part of the fun. I have an old Batronix Galep, the software is quite good. The company still exists and they are still doing the programmer, but I guess you don't want to pay 500 euros just for the little fun to burn something. I hope someone else comes up with a recommendation - otherwise you can check the internet auctions from time to time to look for a used one, or try one of the cheaper chinese copies. Buying chinese material means that you know how to repair and improve stuff, as this is the first thing you do when it arrives. If you can do that, you can save some money, and I still have a lot of fun with the chinese desoldering station from Zhongdi, it goes suck suck suck and there it goes, a fearsome beast with 44 legs. Okay, I lost the track a little.

Erasing: buying an eraser is the best thing you can do, as UVC light makes you blind. If you don't fear that, you can build a box with a switch that turns off the lamp when you open it, and be using a Philips TUV 4W/G4 T5 lamp inside. This lamp is normally used to clean the water for e.g. aquariums, but is perfect for this job. But building that box is more expensive than buying one, so forget it. In that internet auction site look for Eprom UV Timer, the one with the aluminum body is a good one.

Welcome to the club. Let's burn!

EPROM Programmers are cheap as chips these days. For low volume programming I'd recommend one of these: https://www.ebay.de/itm/353542155921

Bryce.

eto

Ok, awesome...

when replacing the Basic/Bios I need the 27C256, right?

Can I also use a 27C512? Looking at the 464 motherboard, it seems Pin 1 (A15) is connected to 5V. And if yes, then with a simple switch on A15 (GND/Vcc) to switch between the original Basic 1.0 and the Basic 1.1?

Bryce

#8
Yes, I've done a tutorial (with fancy pictures too! :) ) here to show you exactly what needs to be done: https://www.cpcwiki.eu/index.php/DualOS . It's the same procedure for the BASIC EPROM, just with A15 instead of A14.

Bryce.

eto

How fast should the EPROMs be? I saw several offers between 120ns and 250ns.

SerErris

The Amstrad should run on an 150ns or faster eprom. The minimal requirement would be some 225 ns for the Z80 memory access, so even a 200ns should work.

Some very good information is here:
http://www.piclist.com/techref/mem/dram/slide4.html

That is not CPC specific, but should match from our ROM perspective very well as the GateArray does not access the ROMs.

My 464 for instance has NEC D4146C -2 RAMs I tried to figure out what speed grade that would be ... but it should be 200ns ... even if many pages in the internet say, that the Amstrad has been equipped with 150ns RAMs.

So essentially in doubt 150ns or faster will do.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

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