Open Source, DIY 512KB RAM Expansion

[TotO]

@VintageAdvantage  If you think that is an insult to remember about the past related CPC projects on a wiki forum, there is a double problem because the CPC has its history and the wiki collect it to not forgot and help serve the future. Adding that he does using less logic circuits can encourage to optimise the TTL design for a future version, at less because handling 1024K here required to add one more IC.

Sorry, I'm not into the "social network" spirit that require to start each sentence by "amazing/great/fantastic ..." (with emoji please)

[revaldinho]

I agree that it's good to be reminded of existing and still supported projects, and Yarek's CPC4MB was definitely a trailblazer for extended RAM in the CPC and deserves a lot of kudos for that.


Both Yarek's and my cards are open source, with schematic and PCB layout files freely available. Both are software compatible, with the available RAM passing the ERAM-tst program provided with Yarek's card. So, yes, there are some good comparisons to be made between the two cards, but counting the number of logic chips isn't one of them because they are very different in design and installation.


I'm not claiming any ground-breaking technology in my card, and there are plenty of other RAM cards around these days if wanting to buy a pre-built one. What I'm offering is a very easy to build card  - one PCB, all through-hole components - based on easily sourced standard logic ICs and which fits externally in any expansion board. DIY builds don't get any easier that this. 


Yarek's project has fewer logic ICs, but is actually spread over 3 small PCBs, using all SMD components, which need to be installed on the motherboard inside the CPC6128 case. You need to desolder all the RAM chips in one RAM bank and then solder in a couple of larger replacement DRAMs together with a couple of NPN Transistors and resistors in their place. A third board (with 3 SMD logic chips on board) sits in the Z80 socket with the CPU reinserted on top, and finally a connection to the PAL is made to have access to internally generated RAM control. This is all shown in the picture attached (from https://8bit.yarek.pl/upgrade/cpc.cpc4mb/cpc4mb1.jpg) and it's this access to internal DRAM address/control signals which is the reason the logic fits in so few ICs. External cards need to recompute many of the RAM control signals for themselves based on only the signals available at the edge connector. This logic isn't totally trivial and that's why most modern RAM expansions choose to go down the CPLD route for implementation.


Anyway, there is it. I hope some people will find it fun and easy to build my simple 74 series card, and it would be especially good if it might encourage new builders to have a go. I feel that Yarek's project is for slightly more advanced builders, and people happy to modify their 'historic' CPC motherboards, but it's good to have options and of course it does provide a full 4MB.


There must be a lot of RAM expansion cards in circulation these days, but the reality is that very little software takes advantage of the 512KB RAM cards let alone the 1MB+ sizes.

[VintageAdvantage]

@VintageAdvantage  If you think that is an insult to remember about the past related CPC projects on a wiki forum, there is a double problem because the CPC has its history and the wiki collect it to not forgot and help serve the future. Adding that he does using less logic circuits can encourage to optimise the TTL design for a future version, at less because handling 1024K here required to add one more IC.

Sorry, I'm not into the "social network" spirit that require to start each sentence by "amazing/great/fantastic ..." (with emoji please)

I do not think that it is an insult, but I find the tone of this specific reply suboptimal, since it has a "I have seen it all / know it all" tone.

I am all for giving credit to previous CPC projects that did certain things first! However, I have a problem if this gets used as a weapon to leash out on some CPC community members, and to glorify others.

I think we have to remember that most of the hardware designs are basically straight-forward adaptations of hardware extension projects that were published in the 80s in various books and computer magazines (some with newer components such as CPLDs... but still). 

Reminding people of "prior art" is one things, but to do it in a way that is derogatory is another! You could have said - "nice, it reminds me a bit of Yarek's RAM expansion from back in the day", rather you pointed out that it is "not new". Which is exactly the spirit that I find problematic.

So, I am reminding people to PLEASE be more enthusiastic and friendly and welcoming about other's CPC projects, and not do it only for folks in your CPC clique and circles. I don't see why this is a prolematic request. 

It is not a community if not all members are treated equally...

And wrt Wiki - the Wiki only has what people put it. Many recent projects are absent from the Wiki, and nobody makes an attempt to complete it. Unless the designers themselves put it in (or how does it work). Again, certain folks a "writing CPC history", and others don't. For example - where is Zaxon's 4 MB expansion, DDI3, etc.? Somebody decided to make the effort to represent certain projects, but did NOT make the effort for other projects. Which is biasing CPC history.

I agree, this is highly problematic from many points of view. The CPC Community and Wiki should strive for a true account and representation of the entire CPC community, and not be a clique circle representation of the "creme de la creme". I am not sure where I read this term, but it was from a certain clique here on the forum.

[TotO]

Please, don't speak for me. Don't said how I have to write (not my native language) when I see the first page of your posts history.
I was here every days during more than 5 years to update the cpcwiki portal and sometime the wiki content... Thank you.

[VintageAdvantage]

I was here every days during more than 5 years to update the cpcwiki portal and sometime the wiki content... Thank you.

I certainly thank you for your service (I have not contributed anything)!
But even CPC community members with great reputation and achievements need a friendly reminder sometimes to be more inclusive I think.. we all need it from time to time.

[VintageAdvantage]

Please, don't speak for me. Don't said how I have to write (not my native language) when I see the first page of your posts history.

And do you know why I acted that way in some of my older posts? I wanted to set an example... but I have stopped with that, it was a bad idea. The idea was to act as a d*** supreme to unite people against the "I have seen it all / I know it all" attitude and make them think a bit before acting in that way, and be more inclusive. So ok, it was a "social experiment", and it was a bad idea. I appologize for that.

[TotO]

I think that nobody his "I have seen it all / I know it all" and it is why the wiki exist around the CPC with not only one contributor.
Now, I apologise that on Internet, since some years (social networks again doesn't help), peoples who are lacking some knowledge goes to denigrate (in group) few peoples having specific knowledges, instead of asking questions. They prefer to destroy the past knowledge to be not annoyed into their vision of the present. This is not specific to the CPC and it is dangerous.

Sorry for the off-topic, now please I think that we can return to the subject.

[VintageAdvantage]

I fully agree with you that it is a balancing act:

- people should respect prior art and CPC history and give credit where it is deserved

- at the same token, we must make sure to continue to be inclusive and open and enthusiastic towards new developments and projects, be it newbies (some of which might have extensive CPC experience, but haven't been part of the community!) or oldies / clique members

- all projects that reach a certain level of maturity should be represented equally, even projects that have a problematic history in terms of "community engagement"

- CPC forum and Wiki should strive for an unbiased account of all CPC activity 

Now back to topic!

[Animalgril987]

Is there 464 fully compatible ( including C3 mode) ram expansion available? Preferably ready made, as I don't have an indoor facility for soldering, and the weather is most definitely not conducive to soldering outdoors.


Also, a source expansion boards such as Mother X4?


Thanks in advance.


Alan.

[Skunkfish]

Hating to plug my own site, but I sell these at www.cpcstore.co.uk

[Bryce]

Hating to plug my own site, but I sell these at www.cpcstore.co.uk

Yes, I can almost feel the hate from here, but you seem to be conquering it quite well

Bryce.

[TotO]

Hating to plug my own site, but I sell these at www.cpcstore.co.uk

Hating to do that, but it is a bit overpriced for a 512K RAM expansion only.

[Skunkfish]

Hating to do that, but it is a bit overpriced for a 512K RAM expansion only.

It was originally priced a little high, as I'd just forked out for the programmer for the XC9536 chips...

I've taken £5 off the price, so it's now down to £24.99

[Animalgril987]

Many thanks, Sir.
I shall in all likelihood order 1 of each after Christmas, if that's ok?


Alan.

[RetroCPC]

Hating to do that, but it is a bit overpriced for a 512K RAM expansion only.

Really? Think about the sales qtys and the time and effort to order components, order PCB's, build PCB's, program and test PCB's, package the product for shipping.... GPB30!!! BARGAIN if you ask me!!! ? I feel offering hardware for the CPC these days is almost offering a service to the community, nobody's going to make a living manufacturing and selling 512K RAM cards for the CPC!!! especially @ GBP30!

GBP30 is very little these days - consider how much it cost to fill your car with fuel or go out for a few drinks (when we could)... its cost me about GBP100 each time I fill the tank... GBP30 would be gone before I knew it...

Personally I'm happy Skunkfisk is here on the forum with his store... IMO we need more new products to keep the CPC alive!

Skunkfisk - I'll be happy to design you some new CPC hardware (I can also build them for you) once I've dug myself out of a 5 year R&D project thats nearing production... Not interested in profit, but just for fun - to help keep the CPC alive

[TotO]

Really? Think about the sales qtys and the time and effort to order components, order PCB's, build PCB's, program and test PCB's, package the product for shipping.... GPB30!!! BARGAIN if you ask me!!! ? I feel offering hardware for the CPC these days is almost offering a services to the community, nobody's going to make a living manufacturing and selling 512K RAM cards for the CPC!!! @ GBP30!

Sure, I can't understand all those things. I'm probably wrong and spoke as a noob.

[RetroCPC]

Sure, I can't understand all those things. I'm probably wrong and spoke as a noob.

no problem, I'm amazed that anyone would go to so much effort for so little return, as I say it can only be for the love of the CPC and its community then a "real" business... also, IMO the Retro CPC scene is very small (and thus quite) compared to say Commodore or Sinclair range of computers...

[TotO]

Sure. May be a day, I will try to give my little of time for the CPC community... Have fun.

[pelrun]

Really? Think about the sales qtys and the time and effort to order components, order PCB's, build PCB's, program and test PCB's, package the product for shipping.... GPB30!!! BARGAIN if you ask me!!! ? I feel offering hardware for the CPC these days is almost offering a service to the community, nobody's going to make a living manufacturing and selling 512K RAM cards for the CPC!!! especially @ GBP30!

TotO is infamous for his stance on hardware pricing; he sells all his stuff with apparently zero margin and believes everyone else should do the same. He's entitled to his principles, but don't mistake his statements for the opinion of the CPC community as a whole. Set your prices at a comfortable level, don't be pressured into something unsustainable. If people value your work they'll want to support you (hell, I have even deliberately overpaid TotO for his products, they're worth it.)

[TotO]

@pelrun  I was famous for making the whole CPC community happy to buy new expansions at a good price around the world.

Don't confuse "the parts price", "the selling price" and "the expected price" by the final user. My prices was not too much low. I have won some money used to provide parts to repair CPC, support cpcwiki and other good actions into the real life. Thank you again for your support.

[pelrun]

You misunderstand. I am not saying you haven't done fantastic things for the community. But you've definitely got a habit of making your pricing opinions known whenever someone starts to make new CPC hardware, and that has definitely convinced at least one person to give up even trying.


There's definitely a middle ground between your prices and the sort of awful limited-edition exorbitant pricing seen in some other retrocomputing communities (*cough*Vectrex*cough*), and people should be encouraged to set prices that are realistic for them and their financial situation, and not be unduly influenced by someone who could technically be considered a competitor.

[Bryce]

Whether you think someone elses prices are too high or too low is an opinion, and everyone is entitled to have an opinion. But, commenting publicly on someones pricing is just bad form. If someone wants to sell their time/effort for a high price, then let them, and if someone wants to sell their products for a low price they can do that too. The customer decides whether the price was good or not, not other hardware producers.

An Apple iPhone and the latest Xiaomi phone are almost identical in all ways, including the technology, parts used and where they were built. The customer decides which one they want to buy and I've never heard an Apple Fanboy complain about the price, in fact they defend it.

Bryce.

[Dubliner]

it amazes me how easily is user support taken out of the price ecuation. The price of a product should not only take in cosideration components price, work and design time and profit, but also have a little margin in case a board breaks or a parcel goes missing, so you can replace or fix the product without losing any money and keeping your users happy.

That is, of course, if you care about user support.

[TotO]

@Bryce  Speaking prices is not something prohibited. It allow to inform peoples about what they bought. Many forums does that.
@Dubliner Please... The registered mail include the insurance to refund the parcel when contracted by the buyer. Stop with that.

[Dubliner]

LOL. I had another infamous guy who doesn't post anymore in this forum in mind when i wrote that. Excusation non petita, accusatio manifesta.