Sharp X-1 Twin Disassembly

[NFG]

Forgive the brevity of this post. I was an hour into this last time when my f**king computer assploded.  I'm so livid I could hurl lightning bolts of rage.

Anyway, carrying on: this is a sort of sequel to a previous PCFX Disassembly.

The Sharp X-1 Twin was a weird combination unit, featuring the X-1 computer (a Z80-based precursor to the X68000) and an integrated PC Engine.  I use the term integrated loosely, the two systems shared the same shell, but little else.  It's more like an Amstrad MegaPC than a Sega/IBM TeraDrive.

Sharp were no strangers to odd hybrid hardware.  They had previously released the Famicom Titler, a Famicom + video titling unit, and the Famicom Twin, a Famicom with a built in Famicom Disk System, and two TVs, one with an integrated Famicom and the other with an integrated Super Famicom.  

It's a real shame they never released an X6800/PCE combo, that'd have been pure poetry, since Hudson did a lot of work on both systems.

Now then, the pictures:


Here she is with her clothes half off.  The standard buttons and ports along the bottom, floppy on the right and a PCE HuCard slot on the left.


You can see how the X68000 Pro was built on a similar design.  The plastic front fascia, the same structural crossbar support, floppies on the right, motherboard on the bottom, expansion slots on the left.


With the rear panel removed you can see how the system sports a lot of empty space.  the motherboard doesn't fill the entire available floorspace, nor does it extend under the expansion bay slots.  From left to right, the ports are Tape Drive (the vast majority of X1 software didn't use floppies), monitor out, stereo AV, and printer.


The floppy riser is a bit odd.  It's socketed for easy removal, but one red wire is soldered to the drive, so it can't be easily removed.  It has two slots on it, one would assume for future expansion with a second FDD, but the cable it's plugged into (not the motherboard, as you might suspect) has two ports in it.  One is glued to the other so it cannot be used.  Why did they put a 2-port cable in, glue one shut and then use this riser, soldered to the drive?  Very mysterious.


Without the front fascia you can see the guts of the system.  It has two atari-style joystick ports, PCE pad port, a volume and power knob that are re-used in the X68000, some LEDs, a game/PC switch, a synch switch (that doesn't seem to have any effect), and two reset buttons, neither of which affects the PCE.


The PC Engine board, not much larger than the HuCard slot.  That's all a PC Engine is, really.  Three chips, some RAM and some supporting capacitors etc.


These are the three PCBs that comprise the entire system.  The PCE, the PCE interface board which does little more than connect the two systems, and the X-1 motherboard.  


The X-1 mobo is densely packed with chippy goodness.  It's loaded with both off-the-shelf and custom chips, driven by a socketed Z80 CPU.


This is the PC Engine PCB.  Only one chip on this side (64kb scratch RAM), and a massive 80-pin connector.  Weirdly this connector has more pins than the standard PCE (69) and is connected to pins on the PCE's chips that no other PCEngine or SuperGrafx uses.  I counted at least twelve pins available to this connector that are not used on any other PCEngine hardware.


The bottom side of the PCEngine.  Three chips (CPU, GPU and video encoder), two video RAM chips, and that's it.  Weirdly Sharp put their name all over it.  I guess they were really proud of their work?


This is the PCE riser/interface PCB.  It's brown, and does little more than connect the X1 PCB to the PCE PCB.  Neither system is in any way aware of the other.  No facilities are shared, the X-1 cannot be used as a dev platform and the PCEngine benefits in no way from the pairing with the X-1.  For all intents and purposes they're simply two systems in the same box.

That said, there are two lines between the two that I couldn't trace.  One is almost certainly composite video, the other one disappeared somewhere en route to the rear of the system.  I'm reasonably sure it's just a sync line or something similar.

The PCE does not output RGB through the X1's monitor port, it only outputs composite video and stereo audio, via the AV connectors.


And finally, the money shot.  It's surprisingly well made, considering its competitors at the time.  Compared to most MSX hardware it's a work of art.

[Endymion]

That is a really beautiful box, and I know so very little about it.

Do you have any info on X1 games?

[NFG]

As near as I can tell the X-1 was about as powerful as an MSX, the games are marginally better than Apple II games, few colours and relatively choppy.  Being able to play PCE games would have been a pretty awesome bonus.

[Midori]

Interesting article, a great experience i my oppinion :-) Disassemble more things!

[FM-77]

Interesting article! I don't have an X-1 yet, and this one definitely looks interesting. The X-1 Twin is really, really expensive though, isn't it?

---
The X-1 games are basically like PC-8801 games. Similiar graphics, similiar sound, etc.

Most of the "bigger" games in Japan got released on PC-8801, X-1, FM-7/77/77AV in the 80's.

[grahf]

I love hybrid hardware, and PC Engine stuff in general. Even though i dont think this makes much sense, its cool nonetheless  

[RobIvy64]

Its interesting to see a 68000 clone manufactured by Sharp... I've never seen that before and i'm pretty knowledgeable on the 68000 CPU. It's probably just a rebadged 68K clone manufactured by Hitachi or Toshiba.

[NFG]

What are you talking about, Robivy?  The X1 is not an X68000 clone, nor does it contain a 68000 CPU, it runs on a Z80.

[RobIvy64]

oohh ok, I thought I saw a 68K in there. my mistake.