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avatar_PulkoMandy

Gemini 1MB RAM expansion for Amstrad Plus

Started by PulkoMandy, 20:34, 08 October 22

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PulkoMandy

No, I take payments only when the boards are ready to ship.

Cwiiis

Quote from: PulkoMandy on 11:54, 17 November 22No, I take payments only when the boards are ready to ship.

Hi Pulko, sorry to bother you, just wondering how this is going? Still eager to get on/a board :)

PulkoMandy

Hi,

I have assembled two boards this week with the fixed PCB layout but they are not working. I'm not sure why yet. Probably I messed up something with the small changes I did to the PCB (the first 10 boards needed a small rework which I incorporated in the PCB this time). I also have supply problems with one of the chips used so I need to find an alternate supplier.

I will get back to this in january.

eto

Just out of curiosity: how do you manage to recognise the lock/unlock sequence with a ATF22V10? 

PulkoMandy

An ATF22V10 plus a 74LS688.

It would be possible to do it in a single chip using an ATF750, but before I can do that, I need to patch my programming software (atfblast) to be able to program the ATF750. The programming algorithm is already reverse-engineered and documented so that should be possible, but I had no time to dig into it. Or someone with a suitable programmer could do it.

PulkoMandy

Quote from: PulkoMandy on 18:35, 17 December 22Hi,

I have assembled two boards this week with the fixed PCB layout but they are not working. I'm not sure why yet. Probably I messed up something with the small changes I did to the PCB (the first 10 boards needed a small rework which I incorporated in the PCB this time). I also have supply problems with one of the chips used so I need to find an alternate supplier.

I will get back to this in january.
Well... it turns out they work a lot better if I solder the correct chips  :doh:

So, I have two boards working but I'll keep one for myself. And I'll not be home for the next week and a half so I will resume assembly and shipping after that. If I manage to order the missing parts until then, I should be able to ship all orders before the end of year.

GUNHED

You do a great job for CPC users. Now it's time to enjoy the time between the years. Sometimes it's a good thing to regenerate the soldering / programming / anything else will work better.  :) :) :)
http://futureos.de --> Get the revolutionary FutureOS (Update: 2023.11.30)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Updated: 2021.12.26)

PulkoMandy

Hello,

Here is the current waiting list (again missing some chips because i can't count... should be delivered in the next few days):

- Amijim
- Tooloud
- Asertus

everyone else should have received a message with payment instructions and I will send the boards as soon as they are paid.

Also, due to a special command, I made a non-plus version of the board for CPC6128 (the ASIC detection is simply removed). So, let me know if you want one of these.

ukmarkh

I'll take a RAM expansion as well if still available. How did I miss this  :doh:

kawickboy


erebos007

Hi ! Newbie 6128+ owner here  ;D
Could you please put me on the list for 1 board when available ?
Thx 

tooloud


Cwiiis

Received mine this morning, thanks PulkoMandy :) Haven't tested it just yet, but will soon - need to get my non-RSF3 expansion setup sorted (M4+Gemini+PlayCity vs my current RSF3+PlayCity)... Feels like a good time to give Unidos a proper go :)

HAL6128

Mine arrived too and it works fine on a Plus (recognised well under SymbOS).
...proudly supported Schnapps Demo, Pentomino and NQ-Music-Disc with GFX

kawickboy


erebos007

Hello,
Board received today  ;D thx 

GUNHED

The Gemini works very well with FutureOS (6128plus enhanced version) - the 1 MB mode and the 512 KB mode equal perfekt.

Thanks for this great achievement.  :) :) :)
http://futureos.de --> Get the revolutionary FutureOS (Update: 2023.11.30)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Updated: 2021.12.26)

tooloud


shacpc

Package received and Gemini working perfectly on my CPC464+ & M4. Excellent support from the author. Thank you.

Apollo

Damn, I somehow missed this thread and additionally, I also didn't know about the RAM extension problem/incompatibility with the ASIC paged into RAM!
Learned something new and, most important, that finally explained why I had some weird bugs with my 6128+ code that I wrote using RAM expansions like Symbiface2! And it seems some people knew about that problem, but it was nowhere documented... :o

@PulkoMandy: I would be interested in 2x 1Mb RAM extensions please, and if you ever decide to bring also a 4Mb version, I gladly would order then at least two as well, as I have use of that for some code I am cooking. (Hen egg problem...)
CPC - My beloved first computer!

andycadley

@Apollo it's one of those things that have been circulating for a little while. I've tried to encourage people not to describe there hardware as Plus compatible when it suffers this issue, but they obviously have reasons not to. It does need documenting, although I'm not sure where is best. I think some of the programming and technical sections need some tidying and structure as it's a bit impenetrable at the moment. I've been thinking of making some Plus tutorials so maybe I'll have a look.

@PulkoMandy you can add me to the list for one. I'll probably never actually get around to using it, but it's a project worthy of some support in my opinion.

PulkoMandy

Hello,

Everyone who has already paid for a board should have already received it.

There are some people who ordered a board but never paid for it, your boards are still waiting until I get a payment.

People who ordered a board today should have received a message, I ahve assembled the boards and they are ready to ship once I have your payments and shipping addresses.

Have a nice weekend everyone!

zhulien

#122
Hi PulkoMandy, just a clarification.

- A 6128plus has 128kb memory, 2 x 64kb banks if you like.  Do both 64kb banks work correctly with a 6128plus when ASIC is paged in? or just the first 64kb bank?

- If we were to use a existing 64kb 3rd party expansion on a 6128plus - this RAM will basically override the internal second 64kb bank of the 6128plus and have the issue?

- With a Gemini

-- if we are running instructions from block 5 (2nd block in the 2nd 64kb bank) and enable ASIC, what happens?

--  With video RAM, if that is put at #4000, and ASIC is enabled - does the CRTC still correctly read the video RAM and not the content of the ASIC RAM?

-- With video RAM, if that is put at #4000, and ASIC is enabled and code is running from block 5 - does the Z80 correctly execute the code and the CRTC still correctly read the video RAM?

andycadley

@zhulien I can answer the first two questions:

1) Both 64K banks of a 6128+ work correctly, i.e. when the ASIC is paged in, no RAM will see the writes to addresses between #4000 and #7fff regardless of what the memory paging arrangement is.

2) Yes, this is the problem with memory expansions designed for older CPCs when used with a Plus machine. They are unaware of the existence of the ASIC registers and will update banked RAM whenever they believe it is paged in. Thus if banked RAM is paged in at #4000, writes in the range #4000 to #7fff will update RAM even if the ASIC registers are paged in. RAM values will therefore become corrupted in a way they shouldn't.

I believe the Gemini expansion is designed such that these issues shouldn't happen, but equally shouldn't upset the normal behaviour of the main 64K - i.e. putting the screen display at any address should work, DMA lists stored anywhere in the main 64K should play correctly etc. I haven't tried it yet as I haven't received mine yet (and would have to spend a while getting my Plus set up in a usable condition once I did).

Assuming it works correctly, the other answers should be:

3) The Z80 will attempt to execute the ASIC registers as code, which will probably end badly. This would fail on a 6128+.

4) That should work. It would on a 6128+.

5) That should not work. The display should still come from block 2, but the Z80 will see the ASIC registers and not the RAM at #4000 - it will thus attempt to execute the registers. This is what a 6128+ would do

PulkoMandy

I'm surprised that you have not received it yet, it was shipped several weeks ago. Well let's wait a bit more, and if it turns out it was lost in postage I'll just send another one...

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