flip

Multicart: yes, the multicart works 'out of the box' with the earlier revision. On the newer ones, they chose to mix two signals which messes with the address selection on the expansion port... I developed the multicart on my only Studio II at the time, which was an early machine... The newer version (up to 140,000 machines it seems) need to have this signal restored - either by modifying the board or by generating the signal on the multicart. That's still being looked at: it will need some additional circuitry. My revision D is in the 6000 serial range. So the one on ebay is only the second one I've ever come across! I am guessing that versions A, B and C never went into mass production and that they switched to E after the first 10,000 or so... I assume the other one is a revision E, but the serial number is unreadable on the pictures. I can't rule out it could be a revision F ;o) Also: i've never seen the serial number on the back match the PCB one. It's possible that some board didn't make it through testing/into a production machine and that the actual number of consoles leaving the factory was lower. Lastly, I don't think there's any cosmetic differences outside that distinguish the different PCB versions - but I could be wrong there...

Very interesting indeed, especially as one seems to be a relatively low serial number [10,929] and a high one [154,024]. They are two different PCB versions - D and E. The main difference is that they use a different latch circuit to select the high address lines.

Incredible that they opted for a single sided board, with an insane number of jumpers. Can't imagine that having been cheaper than making it double sided? Question: does anyone know where to find spare CDP1864 chips? There are a few sites that list them, but when you inquire, they come back saying they're unavailable... flip

Hi, I would be interested in three (3) carts with shipping to Belgium. I realise it'll be a bit of a wait, but well worth it as I understand! Thanks Flip

It's actually easy enough to get a decent composite signal from the console without big modifications. If anyone is interested, I'll put a post together explaining how to do this... flip

I've found the source of the problem with the multicart on 'newer' Studio IIs. As indicated, my original Studio II is an earlier version. The PCB is identified (in the left bottom corner) by a number, ending in 'D'. On newer systems, this is an 'E' at the end. To the right of this are two ICs which are used to select banks of the RAMs and ROMs. On the 'D' revision, these are a CD4011 (4 NAND gates) and a CD4013 (2 D-type flip-flops). On the 'E' revisions, they were replaced by a CD4001 (4 NOR gates) and a CD4042 (quad clocked D latch). The older logic doesn't mix MRD and TPA signals to what is refered to as 'TPA Buffered' in ekeefe's excellent schematic: the CPU's TPA is simply inverted and used as the flip-flop clock signal. It is also directly fed to the cartridge slot. This is what it looks like in a logic analyser: On newer models, the inverted TPA is fed into the 4042's clock before it's NOR'd with the MRD signal. But it's this mixed signal that is fed to the cartridge slot. As it is used as a clock signal for a 4042 latch on the cartridge, it messes up the addressing of the EPROM on the cartridge in some way. If I feed the cartridge slot with the clean TPA signal, things work again! The problem is now that in its present form, the newer Studio II needs a small modification to get the TPA signal to the cart. Not ideal, as not everyone may feel comfortable with that and it probably affects most machines. I am not sure there's an easy way around this... It would probably need a change to the latching circuit on the multicart, but it's not obvious how at the moment. Suggestions, as always are welcome! flip

Hey Tony, If you change your mind about the Visicom, I would be interested. Let me know if you do! Cheers, flip

Hi again everyone, Just an update on the multicart: there appears to be an odd problem with newer consoles. Unfortunately, that seems to be the majority of machines... The cart as it's currently designed works fine on an old machine. The handwritten number on the PCB is below 10,000. On newer machines, some games work. Most notably, the RCA games work as do some of the homebrews. Others simply refuse to initialise and/or crash the system... There's either a subtle hardware change (the older machine doesn't use a 4042 latch/4001 NOR combination, but has a flip/flop and NAND gate to address the different address banks) or RCA updated the system ROM... Since all coding I understand was done on emulators, it's possible they all use an early system ROM dump... I might have to dump the system ROMs from a newer system to compare, but not looking forward to that... If anyone has any idea as to what could cause this, feel free to make suggestions. flip

Hi Fabrizio, I would be very interested in buying this - I will contact you via messaging. flip

Hi all, Proud to present the pcb prototype of a multicart for the Studio II: it has 16 slots, selected by the rotary hex switch. The device works as expected, but there's some unexpected glitches in some of the titles - not sure whether it's my Studio II that has issues or whether something else is wrong... The design for a 128 slot version using 2 switches is as good as ready. The intention is that the PCB will fit in an original shell (thanks to toymailman!), meaning i'll probably need to use a PLCC chip rather than a conventional DIP version (unless I solder it without a socket, but then it would be hard to update). Can't give you a date for a final version, but it shouldn't be too long. flip

Brilliant - thanks. Seems that I had a B0 somewhere instead of BC... flip

Has anyone tried the programming cart mentioned in this post? I've typed in the code in the article, but there's either a bug or something else goes wrong, as the screen seems corrupt for the first few digits appearing... I guess it makes sense to include it in a multicart, since there's enough slots, but it would be nice to know it's working correctly.... flip

I've no idea what the maximum size of the PCB can be for it to fit a case. I only have one cart and am reluctant to crack it open to see... Can I PM you to see whether we can swap a multicart against a case or two? That would allow me to see how everything fits together? Cheers, flip