HALG-CD 4Mb Memory Card

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via this eBay listing

"This card original circuit was fully developed by DoJoe - J. Fenkes and with the great community of keyboard lovers. HALG modified the mechanical, the circuit, and incorporated couple important changes:

✔ The 3 main slide switches that are on the back of the card are stronger now;
✔ The components placement are fully located inside of plastic cover to protect against ESD (electrostatic discharge)
✔ A card enclosure was designed to protect the card when you need to carry around
✔ A plastic case now fits perfectly to cover components and switches;
This memory card is a replacement for Roland’s M-128, M-256 and M-512 cards, as well as the electrically compatible Akai BR-16 and BR-32 cards. Compared to the original cards, this card has two advantages:
✔ It does not require a backup battery. It uses magnetoresistive RAM for storage rather than
regular static RAM, which is a type of RAM that can typically keep its data for twenty years
before it needs to be refreshed.
✔ A single card actually stores 16 M-128 / M-256 cards or 8 M-512 cards, which can be
accessed by a pair of convenient switch sliders at the rear end of the card.
✔ Like the original card, it also comes with a write protect switch.

Installation:
To insert the card into the card slot, the side with the electronic components should face upwards (the same way the side with the arrow would go on an original card).
Configuration:
Whether your card is a 16x256 or 8x512 card is determined by a solder jumper on the card, marked JP1 on the circuit board. It‘s the one circled in green in the image to the right. The jumper consists of three gold pads, two of which are connected by a small blob of solder.
If the left two pads are connected, the card is an 8x512 card, if the right two pads are connected the card is a 16x256 card. There might be solder on all three pads so no pad is obviously golden – just look whether the big solder blob sits to the left or to the right.
This card comes configured 16 x 256K MRAM
With the plastic case is perfect for Roland D550, but you can easily remove the plastic if you desire to fit in other keyboards.
Compatibility List:
While the card design is as close to the original cards as possible, there is a small number of devices that is not yet compatible with our replacement cards.
Tested and fully compatible: Roland A-90, D-5, D-50, D-550, D-10, D-110, D-70, U-20,
JD-800, JD-990, JV-880, JV-1000, JV-1080, JV-2080, R-880 (GC-8), R-8M, GR-1, GR-50,
PM-16, TR-626, Akai MX-1000, VX600.
Mostly compatible: Roland TD-10, TD-20. The card reportedly has errors when inserted all
the way, but pulled back 1/8th of an inch it works fine.
Not compatible: Roland VG-8, Peavey Tubefex.
Some units like the Roland U-110 and U-220 only accept ROM cards, not RAM cards.

Changing the bank size beyond 512 KBit
If you‘d like the MRAM card to emulate PCM ROM cards or a GC-8 system ROM, you can do that
by increasing the bank size. The card supports the following bank configurations:
16x256: The ABCD and 1234 switches work as usual. Pre-configured as this one.
8x512: ABCD works as usual, 1+2 and 3+4 select the same bank.
4x1024: ABCD selects between four banks, 1234 is unused.
2x2048: A+B and C+D select the same bank, 1234 is unused.
1x4096: One bank of 4 MBits only, the switches have no effect.
There are markings around JP1..JP4 on the card, showing how to set the jumpers for a given bank size. Find the line(s) corresponding to your desired bank size and set all jumpers touched by the line to the side that line is on. For example, to make a 4x1M card, JP1 and JP2 would go to the left position, JP3 and JP4 would go to the right position, as shown in the image to the right. JP6 usually does not need to be changed, except if you‘d like a 1x4096 card, in which case it must be changed to the left position.
As a quick hint your card has several banks of memory blank yet. By the very first time the keyboard access that bank, you might see on screen "Illegal Card", but just ignore it and continue with your process. Once the bank is used and has patches on it, you no longer see that message."