I wish I had my Mega PC with me.... Dammit!
Thanks for the advice though - I'll be sure to get all that done and report back to this thread.
by the way, that amstrad reminded me so much to this machine https://plus.google.com/photos/10005...866?banner=pwa (that and next photos) an epson el 3s/33 and the motherboard desing reminded me a lot too to the compaq prolinea 3/XXs https://plus.google.com/photos/10005...306?banner=pwa
Wow! That is a striking resemblance! I cannot believe how hard these AT / Baby-AT based machines are to track down these days. It was pure chance I came across the Mega PC and then EVEN more chance when I found a compatible motherboard to bump it to 33MHz from 25MHz! Not only that but it solved for the most part the NiCad that decided to leak all over the motherboard on the 386SX...
I wouldn't say the resemblance is striking - it's a pretty standard AT setup. I have a IBM 330 with a 486 that is set up the exact same way, including a sliding door in the front.
If you manage to figure out RGB, you could use some Amiga skills to have auto switching between RGB (mega drive) and VGA (PC)
Amigas have 2 video modes, the normal RGB and VGA via a RTG card. Because of this, devices were developed to notice when either was in use and switch the output accordingly (you would still need a multisync monitor though)
Multisync seems to be a bit of a pain. My Mega PC one has some issues with the stand pushing up against the PCB inside the monitor causing the display to collapse into a single horizontal line. Relieving pressure off the stand makes it come good again.
I've hunted down a 4:3 screen for it and from what I understand I need some kind of adapter to run it to 15KHz? Is that more or less correct?
I'm trying to find the pin mappings for the connector, I'm sure I saved them somewhere, but they're buried in my backups.
As you're discovering though, the monitor is VERY important. You need a screen which is capable of supporting a 15KHz horizontal sync rate, which very very few monitors ever did, even "back in the day". I had a lot of old computer hardware, including a large and varied assortment of monitors, but this was the closest I got to finding one that could display the image:
I looked briefly into line doublers to solve this issue, but everything was very expensive, and I managed to get the whole system a year or so later (for $10 as I recall!), so I didn't need to look anymore.I've heard that multi-sync monitors were more common in Japan, and of course there are arcade systems which used a 15KHz sync rate, but in terms of desktop computer monitors, they're few and far between. The TeraDrive is in a similar boat. That said, if you have the correct monitor for the system, you can put the ISA card in any system, and it'll run quite happily. The PC and the Mega Drive hardware have zero interaction in the MegaPC. That's not the case with the TeraDrive, where the PC hardware can interact with the Mega Drive hardware, although I've never dug too far into just how they interact, and what can be done from the PC-side. I suspect it's probably extremely limited.
Last edited by Nemesis; 04-23-2012 at 12:21 AM.
Man, I'd love to see proper motherboard pictures of the Teradrive.
If you really want a 15khz monitor, your best bet is looking at Amiga RGB monitors.
I can make that happen. I actually have two TeraDrive units, one of them a very early build (serial number 201), the other one a bit later (serial number 3 thousand and something I think). The early build has a few hand-wired modifications on the board done at the time of manufacture, while the later model has a lot more. I've always meant to do a lot of testing on the system and document it properly, but there's always 1000 other things to do.Man, I'd love to see proper motherboard pictures of the Teradrive.
One thing I do have for both the TeraDrive and MegaPC is a nice set of documentation and software I believe. It's been awhile since I've got everything out to take a look at it, but I have the full manuals for the TeraDrive at least, along with various versions of the software for it, and I believe I have something similar for the MegaPC. I don't have the manuals or install disks for the "Puzzle Construction" TeraDrive software (only known TeraDrive PC software to interact with the Mega Drive hardware), but it came installed on the hard drive for one of the TeraDrive systems, and I backed up the files off the drive. I messed around with the puzzle construction stuff briefly, and I was able to get it to run. I played around with it a little, but that's about all I did. I always meant to publish a lot of info about this system, and map out what level of interaction is possible between the PC and Mega Drive hardware, but I never got around to it.
Well you always do dozens of awesome things at once for a decade now, so don't hurry on my account. I'm interested in proper board pictures because I want to run a list of Sega part numbers, and unlike the Mega PC (which just used the same chip as in the Megadrive), the Teradrive is fully Sega built with its own part numbers (838-7054 if I see it right on some youtube videos, but I can't see anything else).
Proper pictures would need a lightbox and a proper camera though, and that takes either some time or money.
If he has a Scart capable TV (did they use those in Australia?) and a soldering iron, a vga->scart plug can be done from 5$ and half an hour.
And if he wants to use it in a PC on a monitor (rather than having a TV and a monitor next to each other, as it needs to be in a PC to be powered), as intended. He should use the GBS8220
Ok, I've stripped the newer of the two TeraDrive units down and taken some good pictures of the board:
Most of the chips seem the same as the normal Mega Drive. The FM chipset in this case is a discrete YM3438, which we know is effectively the same as the YM2612. Apart from that, you've got your standard 315-5313, 315-5364, and 315-5309, same as an early model 1 Mega Drive. Probably the two most interesting chips on the board are U18 and U20. U18 has its board label partially covered by the green wires in those pictures, but it's labeled as "BUS SW". U20 is labeled as "DISP SW", and the writing on the chip didn't really turn out in the photos, but its markings are as follows:
These two chips probably handle all communication between the two systems. I haven't traced any connections, but I think it's quite likely that the PC hardware is able to halt the M68000, and read/write into the Mega Drive RAM at the very least.
No SCART here unfortunately. We have composite with RCA jacks - they aren't that bad though.
Looks like I had better grab up one of these GBS 8220 devices. They sure are cheaper than I was expecting too. Thanks for the point in the right direction guys!