Gemini 1MB RAM expansion for Amstrad Plus

[TotO]

I had a dream. A dream where all CPC software used 256K of RAM as standard since 1992... From there, I will understand this sudden need to have 2048K and more, 30 years later. But I remember that using more than 64K was taboo 10 years ago.

[andycadley]

Once you get past about 256K, having to manage memory in small chunks of 16K just becomes painful. Inevitably the only real approach beyond that point is to fake a mass storage device and just "LOAD" data into main memory instead.

And once you do that, the benefits of it being visible to the CPU as RAM instead of just being a mass storage device are remarkably small.

[Prodatron]

Cool thing about the CPC memory banking is (at least compared to ZX Spectrum and Atari8bit), that you can map whole 64K banks into the visible Z80 address space. That is already a big benefit for handling code and data areas inside the extended memory.

The progress regarding memory expansions for 8bit machines is quite interesting:
Level 1.) C64: only DMA transfer, no possibility to execute code inside external memory
Level 2.) ZX Spectrum, Atari8: can switch single 16K into a part of the visible area
Level 3.) CPC: can switch 16K and even 64K into the visible area, but with limited possibilities
Level 4.) MSX, PCW, Enterprise, NCxx0 etc: can switch any parts of the extended memory into the visible 64K in 16K blocks

Sam Coupe is somehow between 3 and 4 due to its limited 32K pages.
There are some more curiosities like the MTX500/512/RS128 which have banking possibilities between 2 and 3. Or the strange MMU of the C128, which could handle 512K but then was restricted to 128K as the Commodore management didn't like to have it too powerful.

[roudoudou]

If someone shows me a real working example of a software, which does useful things with so much RAM (>1MB) which can't be done with a mass storage device, I would be convinced. All I see now are video- and audio-streams or theoretical blah blah.

in an arcade game, some delta animations for background could use hundred of kb
in a platform game, depend of what you target as animation quality, you can rise as many MB as you want
it doesn't matter that i had only 8MB with my Pentium back in days if i can do a top notch Amstrad CPC game with moaaaaR !

as an example, this short preview of a pending project need at least many ROM (but huge RAM capacity may be fine)

[Prodatron]

Wow, fantastic animations!

[zhulien]

Well, seems mass storage on CPC now is qutie plentiful and common and that itself gives the possibiliy of some interesting games which can exceed the space of a DVD ROM if desired.  I would see 16mb on a CPC besides some specialty uses, as a perfect cache for potential megasized games that would otherwise keep accessing the quite fast mass storage.  Of course I am happy with 4mb too, but 16mb or 16gb even is pretty cool if implemented in a quite cheap way - at least we can put a large number on the reset screen that isn't a lie.

[GUNHED]

Now I am just curious, does that mean that your FutureOS is crashing with a normal memory expansion on a CPC plus with plus features enabled?

Thanks god no. Our FutureOS always worked with any kind of RAM expansions on the 6128plus. We just had the luck that the access to the memory mapped I/O (ASIC) is usually done when the main RAM is banked in.

However in the machine monitor you can select an 16 KB expansion RAM block between &4000 and &7FFF and then access the memory mapped I/O too. This can serve to check for possible problems with certain expansions. Well, I'm sure there are other ways too. For sure somebody did already such a test program.

Personally I never ran into the problem (of ASIC being enabled, accessed and E-RAM being active), but it's AWESOME to have the Gemini expansion.

I'm fully aware that your SymbOS supports a maximum of 1 MB, so for SymbOS 1 MB is fine of course.  However,  4 MB would be just awesome for the native OS and also for FutureOS.

And I'm really looking forward to the possible 2 MB expansion of course!!!

[tronic]

If someone shows me a real working example of a software, which does useful things with so much RAM (>1MB) which can't be done with a mass storage device, I would be convinced. All I see now are video- and audio-streams or theoretical blah blah.

in an arcade game, some delta animations for background could use hundred of kb
in a platform game, depend of what you target as animation quality, you can rise as many MB as you want
it doesn't matter that i had only 8MB with my Pentium back in days if i can do a top notch Amstrad CPC game with moaaaaR !
as an example, this short preview of a pending project need at least many ROM (but huge RAM capacity may be fine)

Totally agree about the delta animations and what Roudoudou says...
I'm often frustrated that I can't add many more frames due to lack of ram when I do some deltas tests* for fun... Mainly demo oriented effects...
This is even more true for a game with delta animations... And obvious in the posted video above...

*A few here (in 128kb only, unfortunately...) :
https://rasmlive.amstrad.info/edit/GQufxj9uuQjjczmfn
https://rasmlive.amstrad.info/edit/EenmF7REYnmg2KhMF
https://rasmlive.amstrad.info/edit/nnwQBDAAoBdodm6Xm
https://rasmlive.amstrad.info/edit/qj7HjpBHJuGN7EJNp
https://rasmlive.amstrad.info/edit/XrcagxGAQSmtTqJvE
https://rasmlive.amstrad.info/edit/iL3rBFiMxpqfbmPJn
https://rasmlive.amstrad.info/edit/GeWAdbAHTBQjrCvWp

Best.
Tronic/GPA.

[GUNHED]

@PulkoMandy : Please put me on the waiting list for one ingenious Gemini RAM expansion. 

[Nemo59]

Hi, I'm interested by one board Gemini! 

[kawickboy]

You can count +1 for me please. Especially if a symbos plus release is on his way.
1Mo, 2Mo, 4Mo, 16Mo... I'm in.

[amijim]

Hello, I am also interested in one unit. Thank you. 

[Cwiiis]

I'm trying to be patient, but my curiosity has gotten the better of me... Is there any progress on this @PulkoMandy ? Eagerly awaiting

[PulkoMandy]

Hello,

The first 10 boards have been shipped last week. This was my initial batch to identify any problems with the design, and indeed there was one small problem that I had to fix while assembling the boards.

I will make an order for the next 20 boards PCBs and components soon, I've been busy with other things lately. And after I order them it will probably take ~3 weeks for the PCBs to get delivered, and then a bit more for me to assemble and test the boards.

[Nemo59]

Excellent! How to place an order for a delivery in France?

[PulkoMandy]

I have taken note of your order already, I will send you a private message when the board is ready with payment instructions 

[Titi]

Hello,

The first 10 boards have been shipped last week. This was my initial batch to identify any problems with the design, and indeed there was one small problem that I had to fix while assembling the boards.

I will make an order for the next 20 boards PCBs and components soon, I've been busy with other things lately. And after I order them it will probably take ~3 weeks for the PCBs to get delivered, and then a bit more for me to assemble and test the boards.

Please put me on the waiting list for one Gemini RAM expansion.

[Prodatron]

My arrived today! Thanks a lot! I will try them soon with my 6128 Plus. I am especially very curious about the ASIC leds, will probably look quite cool.

[Maniac]

Mine arrived yesterday thank you. Will try it out at the weekend if not before. Looking forward to trying it out.

[GUNHED]

Mine arrived yesterday thank you. Will try it out at the weekend if not before. Looking forward to trying it out.

Happy weekend then! 

[zhulien]

But is there any software that really makes use of it? Because the list of software on that Wiki page is just memory testers... If that's all you want to do, it's easier to write software that just pretends the memory is there and working fine 

Have you tried AMDRUM (and the later LambdaSpeak Speech Synthesizer) ?  I know there are better software for every more modern computer, but AMDRUM on Amstrad CPC is actually quite fun and usable - now it achieves some really awesome results with only 64kb!  Imagine if you have 16mb (or even 4mb) of sample RAM. That is only 1 use, in the end it depends how well it gets adopted and breaks that chicken egg situation - but I can say that nothing will ever happen without the RAM expansion before the software - or... perhaps some software could almost be there.

[Richard_Lloyd]

Arrived in the UK. Weekend playtime coming up!

[tooloud]

I will make an order for the next 20 boards PCBs and components soon, I've been busy with other things lately. And after I order them it will probably take ~3 weeks for the PCBs to get delivered, and then a bit more for me to assemble and test the boards.

@PulkoMandy Put me on the list please I have Amstrad CPC6128+ waiting for it Can you estimate cost with shipping (01-318 Warsaw, Poland)?

[PulkoMandy]

The cost is 35€ with shipping included, no matter where you are.

[tooloud]

ok, put me on the list please, if you need pre payment now let me know on PM. Thanks!