SVI-606: Info needed to repair

Prophet (2619)

23-02-2021, 18:48

A friend has found a badly damaged SVI-606 and after fixing some of the visible problems (mainly broken connector and traces) and replacing some ICs, he's trying to read the ROMs to check if they're good.
The SVI-606 seems to have two ROMs, an OKI mask ROM M38256-71 and an EPROM. The mask ROM suposedly it's a 27256 compatible IC; but after reading, he only gets a bunch of $FF values...looks no good at first sight.

¿Has anyone more info about this adapter?, ¿how it works and what kind of ROMs it uses (BIOS, firmware, glue-code, etc.)?. And of course, ¿are the ROMs dumped?.

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Par sdsnatcher73

Prophet (3019)

24-02-2021, 05:44

I don’t think the ROMs have been dumped. After the repairs has your friend tried the adapter to see if it works? I have no experience dumping mask ROMs but I have seen suggestions to put the chip on a cartridge board and read it from an MSX.

Par jltursan

Prophet (2619)

24-02-2021, 09:11

Thanks!. Yes, he has tried it without success, that's why he's trying to check the ROM. Seems that you're right, the M38256 mask roms can be hard to read with an EPROM programmer; but you're suggestion about putting it into a MSX cart is a good one.

I'm pretty curious about how it works as a MSX. The hardware matches a low spec MSX1; but I have no idea about how it interfaces with the native SVI hardware or what kind of BIOS it must have.

Par sdsnatcher73

Prophet (3019)

24-02-2021, 16:58

Yeah a nice find of very rare piece of kit. If you get it working please share some videos of it in action

Also would be cool to see some pictures of the internals. Does it have it’s own Z80 or does it use the one in the SVI?

Par msxholder

Champion (399)

24-02-2021, 22:30

Is it version 1.0 ?
there is no keyboard and no Z80 in SVI606.

Par NYYRIKKI

Enlighted (5918)

24-02-2021, 23:12

Yes, SVI-606 does not need own Z80 as the SVI expansion bus has a set of pins that allow you to perform a lobotomy to the machine. By using this zombie mode it was possible to recreate the memory handling and puppet master the VDP from the extension. This trick allowed creating these Colecovision and MSX adapters.

Par jltursan

Prophet (2619)

02-03-2021, 18:50

Some pics: