Author Topic: Memory Expansions  (Read 1171 times)

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Offline blackdalek

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Memory Expansions
« on: 08:51, 01 January 18 »
I'd like to try out some of these alternate OS for CPC like Symbos etc. so I figure I should probably look into getting a memory expansion.

Back in the day, all you could get were Dk'Tronic memory expansions, but nowadays other options are available.

What memory expansion hardware is available out there today and what are the pros/cons of each?
CPC6128 modded with ABBA switch. External 5.25" floppy drive with side switch and Multiface 2. Now also sporting a joystick splitter and M4 WiFi board.

Offline GUNHED

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Re: Memory Expansions
« Reply #1 on: 18:09, 01 January 18 »
The best pick would be the X-MEM from Tot0. It contains 512 KB RAM and 512 KB Flash-ROM. That's perfect for alternative OS (like FutureOS and others), they like to be in the ROM area.


As alternative you can use the M4 card, which also provides 512 KB ROM space, but no RAM expansion.


Further on there is the Z-MEM, which contains 1 MB of RAM, but no ROM.

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Offline blackdalek

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Re: Memory Expansions
« Reply #2 on: 22:50, 01 January 18 »
Tot0, having seen my post, has already been in contact with me about X-MEM and Z-MEM :)

But your reply to my post has provided further useful information. Thanks!
CPC6128 modded with ABBA switch. External 5.25" floppy drive with side switch and Multiface 2. Now also sporting a joystick splitter and M4 WiFi board.

Offline msmthng

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Re: Memory Expansions
« Reply #3 on: 19:08, 05 March 18 »
The best pick would be the X-MEM from Tot0. It contains 512 KB RAM and 512 KB Flash-ROM. That's perfect for alternative OS (like FutureOS and others), they like to be in the ROM area.


As alternative you can use the M4 card, which also provides 512 KB ROM space, but no RAM expansion.


Further on there is the Z-MEM, which contains 1 MB of RAM, but no ROM.


has anybody experience with z-mem in combination with m4 wifi? my cpc doesn't start propperly if i plug them together?
thx

Offline Shaun M. Neary

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Re: Memory Expansions
« Reply #4 on: 20:57, 05 March 18 »

has anybody experience with z-mem in combination with m4 wifi? my cpc doesn't start propperly if i plug them together?
thx


Yep. Trying to get those two together was an exhausting experience despite all the help in the world from both Duke and TotO on this. The following advice is from my own experience although I know others who's work flawlessly, so your mileage may vary. This setup was on a CPC464


A few suggestions
1. Power the m4 externally with USB, Symbos may struggle with both powered from the expansion.
2. At present, Symbos won't pick up 1mb, disable the upper rom bank on the zmem.
3. For max compatibility, m4 in rom 7, parados in rom 6.
4. If you happen to have talreks MFII clone, remove it. I can't get it to play ball with the zmem at all.


Good luck!

Offline msmthng

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Re: Memory Expansions
« Reply #5 on: 21:27, 05 March 18 »

Yep. Trying to get those two together was an exhausting experience despite all the help in the world from both Duke and TotO on this. The following advice is from my own experience although I know others who's work flawlessly, so your mileage may vary. This setup was on a CPC464


A few suggestions
1. Power the m4 externally with USB, Symbos may struggle with both powered from the expansion.
2. At present, Symbos won't pick up 1mb, disable the upper rom bank on the zmem.
3. For max compatibility, m4 in rom 7, parados in rom 6.
4. If you happen to have talreks MFII clone, remove it. I can't get it to play ball with the zmem at all.


Good luck!
Thanks, powering the m4 using usb was the hint. it is starting up now.


Offline Shaun M. Neary

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Re: Memory Expansions
« Reply #6 on: 21:45, 05 March 18 »
Thanks, powering the m4 using usb was the hint. it is starting up now.




It still should have powered up though. But some games crashed when I didn't use the USB (128k Untouchables being a big one). But as I already mentioned, different configurations may have different results. What's your configuration?


Also tagging @Duke in here. He'd be interested in this news given my recent houndings to him.

Offline pelrun

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Re: Memory Expansions
« Reply #7 on: 05:44, 06 March 18 »
The expansion connector generally makes a fairly poor connection (30 year old cheap uncoated copper traces will do that...). The resistance in the connection means that the more power the external devices try to draw (or the more devices you add), the lower the voltage drops even if there's plenty of headroom on the CPC side. Since everything is designed for 5v, it gets unhappy when it sees 3.5v instead.


If adding an external power supply fixes the problem, then you should give the edge connector a clean. It still might not be enough to let you run directly off the CPC, but it's likely that the other pins on the connector are marginal as well.

Offline Bryce

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Re: Memory Expansions
« Reply #8 on: 09:37, 06 March 18 »
(30 year old cheap uncoated copper traces will do that...).

The expansion contacts are tin plated, still shit, but tin plated :)

Bryce.

Offline pelrun

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Re: Memory Expansions
« Reply #9 on: 09:47, 06 March 18 »
Ah yeah. Mine have been solder coated long enough that I can't remember what they originally looked like  :laugh:

Offline GUNHED

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Re: Memory Expansions
« Reply #10 on: 12:44, 06 March 18 »

has anybody experience with z-mem in combination with m4 wifi? my cpc doesn't start propperly if i plug them together?
thx


From another user I know that they work fine (using FutureOS). But the M4 needs exactly 5 Volt, so it can help to provide power using it's USB power plug.  :)
http://futureos.de --> Get the revolutionary FutureOS (Recent update: 2019.01.14)
http://futureos.cpc-live.com/files/LambdaSpeak_RSX_by_TFM.zip --> Get the RSX-ROM for LambdaSpeak :-) (Ver.: 2018.08.15)

Offline rpalmer

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Re: Memory Expansions
« Reply #11 on: 14:19, 06 March 18 »
What are the exact symptoms you experience with the setup msmthng?
- Does the CPC boot up into basic?
- Does the Z-Mem not even register with other software?
- Does the M4 Wifi not even work (no support routines available to access it)?

It is a little hard to know what the problem you have with so little info to work on.

As had been mentioned, people have had no problem.

rpalmer

Offline msmthng

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Re: Memory Expansions
« Reply #12 on: 07:20, 09 March 18 »
Without additional powering. The cpc didn't start, the m4 was available on WiFi. With us power or powering the MotherX4 the combination works fine. Iam not able to execute the memory checks from ToTo but the memory is available in SymbOS.

Offline rpalmer

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Re: Memory Expansions
« Reply #13 on: 14:05, 09 March 18 »
Without additional powering. The cpc didn't start, the m4 was available on WiFi. With us power or powering the MotherX4 the combination works fine. Iam not able to execute the memory checks from ToTo but the memory is available in SymbOS.

The very fact that you need additional power suggests that maybe the CPC has "lost" enough power to supply external devices. This may be due age related degradation of components (however this is hard to pin down) and when these failed they fail at a moments notice and not like a mechanical device which we can predict with more certainty.

With additional power it seems that may be Toto software has an issue with certain setups. However, SYMBOS seems to see it okay and so may there is no problem when powered externally.

I take it you tried each on their own to see the CPC can use each device with no issues.

rpalmer

Offline Bryce

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Re: Memory Expansions
« Reply #14 on: 14:32, 09 March 18 »
The power consumption of the CPC doesn't really change much (if at all) over time. However, contacts do get oxidised and there will be an associated voltage drop due to this, not just on the expansion port, but also the power socket, power switch, power header on the PCB and many other connections that the power crosses before it gets to the expansion in question.
As well as that, the traces that carry the power to the expansion port aren't dimensioned to carry a high current, so as the current rises they will begin to get warmer. As copper has a positive temperature coefficient (ie: the warmer it gets, the higher its resistance) it will start to drop more voltage in the trace itself as the current requirements rise. All this together can mean that the perfectly fine 5V that your PSU produces at its plug, could be a not so fine 4.5V by the time it gets to the expansion. Swapping to a 16A PSU won't help either, because it's a voltage drop issue, not a PSU current limit issue.
Thorough cleaning may improve the situation, but we have to live with the fact that we are pushing the CPC to its power limit when we add many expansions to the CPC at the same time.
This can cause confusion on occassions when multiple expansions all work fine on their own, but start malfunctioning when used in conjunction with other expansions.

Bryce.

Offline rpalmer

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Re: Memory Expansions
« Reply #15 on: 13:14, 10 March 18 »
If the only expansions are the Wifi and Memory expansion, then its begs the question if the design is okay with respect to power consumption and other devices connected to the bus.

These two devices should not in theory consume more power than what the CPC can handle. However, there is the USB port for additional power to the Wifi which seems to help and lends further weight to the fact the using an external power supply seems like a must for newer devices for the CPC. This seems contradictory since modern ICs are for the most part low power.

rpalmer

Offline 1024MAK

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Re: Memory Expansions
« Reply #16 on: 21:02, 11 March 18 »
It's not the nominal 'relatively low' current that causes the problem, but the instantaneous peak demand when the outputs of the modern chips change state (all eight data lines for example could change state simultaneously). This sudden current demand may cause a local drop in the voltage seen at the power pins of the relevant chip. If the supply voltage is already marginal (due to the voltage losses that Bryce gave details of above), then the voltage at the chip may drop below an acceptable level. This may cause all manner of strange symptoms.

Mark

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