What is the cheapest way of adding more fast ram to an A1200

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I have pretty much rebuilt my Eyetech Ez tower with my A1200 board installed. Unfortunately I appear to have lost some Amiga kit since it was last up and running and I don't have my Power up board anymore (gutted)
I would like to put some more memory in my Amiga though and since technology has come a long way since my Amiga was last up and running I wondered if there are now any cheap options (say under £40) for adding more memory? Not bothered about CPU upgrades or anything else just just something that give me at least an additional 4MB or 8MB so I can install Amiga OS 3.5 on my HDD.
 
This would be the closest to your price point and feature requirements but I don't know if you can still get one new.
Other than that you can keep checking for the occasional RAM-only A1200 expansion that pops up here.
Avoid PCMCIA-port SRAM cards, of course.
 
If you got a trapdoor expansion for under 40 these days it would be a miracle.
 
This would be the closest to your price point and feature requirements but I don't know if you can still get one new.
Other than that you can keep checking for the occasional RAM-only A1200 expansion that pops up here.
Avoid PCMCIA-port SRAM cards, of course.

Thanks for the link. That one is currently out of stock so I will have to keep my eye out for it coming back in while I look for a slightly cheaper option.
I am suprised there are no new RAM only expansions for the A1200. I am no expert on electronics but I would not have thought it would be too much work to build a 4 or 8MB memory upgrade card without needing to put a CPU on the board as I am assuming that is where all the cost is on the accelerators.
It seems a lot of the new memory upgrades are made for the A500 / A600 rather than the A1200.
 
It seems a lot of the new memory upgrades are made for the A500 / A600 rather than the A1200.
I think it's because there are no sources for the A1200 trapdoor connectors (the Apollo team have had to get them manufactured especially), where as the A500/600 just use sockets over the CPU.
 
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I guess having to have the connectors specially made is going to add to the price. Are there any new SRAM cards that plug into PCMCIA that don't slow the A1200 down?
 
I guess having to have the connectors specially made is going to add to the price. Are there any new SRAM cards that plug into PCMCIA that don't slow the A1200 down?

The interface is 16 bit so, sadly, no.
Let alone prices are generally too high there, too :)
 
Did any company ever produce a memory upgrade that plugged into the clock port of the A1200? From reading on the original specifications of the clock port it was designed to allow Commodore to put extra memory as well as add an RTC. If not, it must be easier to add memory this way as the clock port is a very simple connector compared to the expansion port connector.
 
Did any company ever produce a memory upgrade that plugged into the clock port of the A1200? From reading on the original specifications of the clock port it was designed to allow Commodore to put extra memory as well as add an RTC. If not, it must be easier to add memory this way as the clock port is a very simple connector compared to the expansion port connector.

The "clock port" is the reduced set of pins you see on later A1200 revisions and cannot be used for RAM expansion.

The full set of pins present e.g. on revA A1200 boards could indeed support both a RAM expansion and a real-time clock.
But that was only because the initial plan was to install only 1 MB of chip RAM on the A1200 - so the second MB of *chip* RAM, along with a possible RTC, could be added with a suitable plug-in board.
But eventually the A1200 was launched with the full 2 MB, so the full connector became redundant as it could only be used for chip RAM, and was later reduced to the clock-port only connector, which is far too limited for a RAM expansion (only has 4 address lines IIRC).
 
Damn, thought I had found a loop hole. :D
Guess I will have to keep my eye out for someone selling a cheap RAM only expansion
 
My guess is that the cheapest solution would be to look for an ACA1221 or ACA1221ec. If you can find a non-upgraded version of the old 1221 (without ec), it should be the cheapest of the two, however since you cannot get it from new any longer it may not be easy to find. The cheapest might be a 4MB SRAM card however as pointed out, since it is 16 bit, the speed is not optimal. It can be used in a pinch though and it can always be sold on to some A600 user when you decide to get a proper A1200 trapdoor upgrade. :)
 
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Remember price discussions aren't allowed
 
Damn, thought I had found a loop hole. :D
Guess I will have to keep my eye out for someone selling a cheap RAM only expansion

You are correct. You have found a loophole.
The schems clearly show the connectors P9A and P9B can support a full memory expansion. The small section of P9B that is populated is for a small RAM expansion and the A1200 schems mention that the small section that is populated is "For 2MB Memory board".
If the connectors at P9A and P9B were fully populated, they could support a larger RAM board since all the required signals are present on the fully populated connectors.
It would be very easy to simply suck out the solder on the PCB where the holes are at P9A and P9B and solder in the correct number of header pins. No fancy tools are required, just a cheap manual solder sucker and a soldering iron.

I'm sure it wouldn't be difficult for someone who knew what they were doing to design and produce a large RAM board that plugs into the connectors.
It would actually be a great project and I'm sure a lot of people would be interested to purchase one.
The connectors are common off-the shelf dual 2.5mm header pins which are exactly the same as the IDE44 connector except with 4 pins less (40 pins total on connectors P9A and P9B).
So all it needs is for someone to step up and take on the challenge :)
 
@fordav1


Unfortunately that's not the case :)
If you put a 2 MB board there it will simply mirror the existing 2 MB on the A1200 motherboard. And of course you can't go beyond 2 MB either, that's a hardware limit.


What you suggest could have some use as a way to sort-of piggyback the onboard RAM chips and quickly confirm RAM faults, but since Commodore removed most header pins (only revA boards have the full set, and those are a scarce minority) noone would bother soldering header pins for that, there are other ways to confirm RAM faults anyway.
Let alone the pins would have to be desoldered afterwards as some clock-port expansions rely on their absence since they occupy the same space :)
 
The schems clearly say "Memory Expansion" and it has the full 32-bit data bus joining to Alice. The schems specifically mention that the 22 populated pins are for the "2M-Byte PCB". The fact that C= specifically mention a 2MB memory expansion with only the 22 pins used means the full connector (P9A+B) supports more RAM, or at least supports more of something.
If it mirrors the first 2MB of chip RAM, then those chips on the motherboard could be removed and the top board could give 2MB Chip plus whatever else it has on board as Fast Ram. Or some logic/CPLD can switch it to Fast RAM or whatever like the ACA500+ does with the 512k expansion Slow RAM that turns it into Chip RAM. Any memory expansion that is made now can also have the extra 22 pins on it for any other 'clock port' expansion to plug into on top and jumpers or whatever to disable some parts as required and/or implemented some way. Regardless of clock port uses (which I'm not talking about here) the point is that connector can support way more than 2MB. I suppose it might have been in the plan for a 4MB or 8MB chip RAM add-on (like the unimplemented A4000 8MB Chip motherboard jumper), but there's no info to suggest that.
It's also possible that Alice actually supports more Chip RAM but no one at C= let that cat out of the bag since they were planning to sell an expansion later. Since Alice is soldered and the A4000 had a jumper to give more Chip RAM it suggests that there was an easy plug-in upgrade planned that did not require any chips to be replaced. I suppose only the engineer who designed the A1200 would know the true purpose of the connector.
I'm curious about this 'hardware limit' you mention? What hardware limit?
 
Quote from this document:
https://github.com/rkrajnc/minimig-mist/blob/master/doc/amiga/aga/A1200FuncSpec.txt

2.8.2 A1201 or Memory Expansion/RTC

Two 40 Pin DIL headers have been provided on the A1200 for a
Memory/RTC expander. The A1201 Memory Expansion Card can
have 1MB of DRAM organized as 256K x 32 and/or a battery backed
up RTC. On A12OOs with 2MB of DRAM on the motherboard, the unit
may only provide a 22 pin header for RTC support. This card is
installed through a removable top opening in the PCB shield.
 
From the way it is written it's looks like a preliminary document. All I can say is Wow they sure weren't thinking very far ahead into the future. What a waste of a potentially great upgrade path.
 
It says 28th October 1992 in that document and the 1200 was released one week before on the 21st, so I guess it should reflect the final specs (more or less). It does also specify the final 2MB design so they probably didn't bother update this section to reflect the fact that they were only shipping 2MB models. Perhaps at this time they were still considering releasing a cost reduced version with only 1MB chip. But it doesn't mention anything about fast mem on that header. But shouldn't fast mem also be located on a different bus than chip mem?

Regarding thinking ahead, it is always easy to comment on past choices but back then they didn't have all the information we have today. It would be so much easier to design new products if one could look into the future. :)
 
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From the way it is written it's looks like a preliminary document.
Yes the schematics show some things never realised on actual A1200s.

All I can say is Wow they sure weren't thinking very far ahead into the future. What a waste of a potentially great upgrade path.

They had bigger fish to fry. AGA was not the intended upgrade path.
The real upgrade path had been the AAA chipset (since 1988-9 and totally incompatible with AGA) but it was delayed and they wanted to release new products, so the AGA chipset was put together in 1992 as a "quick and dirty" remake of ECS. In principle, they're identical.
So yes, they weren't thinking far ahead with AGA, but with a good reason.

(eventually AAA was cut short and replaced before release with Hombre, which also died unreleased along with Commodore in 1994)
 
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