For the retro gaming enthusiast, nothing beats original hardware. The feel of the controllers and the exact timing of the original, non-emulated software provide a certain experience that’s difficult or impossible to replicate otherwise. To that end, [bit-hack] wanted to play the original EGA, 16-color version of The Secret of Monkey Island in a way that faithfully recreated the original and came up with this FPGA-based PC with a real NEC V20 powering it all.
The early 90s-style build is based on a low-power version of the V20 called the V20HL which makes it much easier to interface with a modern 3.3 V FPGA compared to the original 5 V chip. It’s still an IBM XT compatible PC though, with the FPGA tying together the retro processor to a 1 MB RAM module, a micro SD slot that acts as a hard disk drive, a digital-to-analog audio converter, and of course the PS/2 keyboard and mouse and VGA port. The mouse was one of the bigger challenges for [bit-hack] as original XT PCs of this era would have used a serial port instead.
With a custom PCB housed in a acrylic case, [bit-hack] has a modern looking recreation of an XT PC running an original processor and capable of using all of the period-correct peripherals that would have been used to play Monkey Island when it was first released.
FPGAs enable a ton of retrocomputing projects across a wide swath of platforms, and if you’re looking to get started the MiSTer FPGA project is a great resource.
Quite nice. I wonder how compatible it is with other software, and also why the NEC V20? If all other hardware, including AdLib and VGA, are emulated, the CPU is the lease difficult thing to also emulate :).
Thanks :) Yes I could have used an open source soft core 8088 such as the MCL86, but I quite enjoyed the idea of having a real CPU on the board, and I had a bunch of them in my parts bin already. Software compatibility can be so so, I find that most CGA software works but my EGA support needs a lot more work.
I wrote a 486 PC emulator in C, and yes EGA/VGA is very tricky to get working 100%. It’s the hardest part after the CPU. Mine still isn’t flawless, but it’s about 90% there.
I love your FPGA project, good job!
Hi! I suppose because V20 chips are still readily available.
And because the CPU is considered heart of the system,
so using the real thing means less emulation (FPGA just serving as the chipset).
All in all, this configuration qualifies as a “Turbo XT” PC of early 90s.
They were highly integtrated and not seldomly had been upgraded with AdLib/Sound Blaster and VGA.
Have a look at “Juko XT” series of mainboards for example. :)
Very compact, including with special V20/V30 support sometimes (for duty cycles etc).
Some had EMS and other stuff in the chipset. Very cool.
Imagine if we could take this back to mid 1980s and showed we could make XT the size of a wallet, use just mere mA of power, and worked decently like the big, bulky, and power guzzling counterpart?
That was already a thing, there were PCs that kind of size back then, the power consumption wouldnt have met spec though.
I second that. Highly integrated XTs existed in the 1980s.
Palmtop PCs, too. The Atari Portfolio, the Poqet PC..
That’s also the reason CGA support in both software/hardware had been kept for so long, I think.
Portable PCs had LC displays that had 640×200 or 640×400 pixel most of time.
The 640×400 models often were line doubled like on an Olivetti M24/AT&T 6300, which on LCDs also fixed aspect ratio a bit.
Native mode also used 640×400 resolution in monochrome (aka “DCGA” for double CGA?).
Then there were people who ran AutoCAD, MS Excel or dBase
on the go on a tiny palmtop the proportions of less than a VHS tape. In CGA..
Here’s AutoCAD on an early 90s model of such a palmtop.
https://www.youtube.com/watch?v=SqyKiSVILDM
VGA displays in 640×480 pixels had existed in the late 80s,
too but were reserved for higher end models.
Such as Compaq SLT 286 laptop.
I do miss my Zenith MiniSport…..
Wow! It even had its own 2″ floppy disķ! That’s so cool! 😎💙
https://www.storagenewsletter.com/2018/11/06/history-1989-2-inch-floppy-disk-lt-1-made-by-fujifilm/
A great retro computer.
May I ask how to open a blog?
An incredible feat just to play one of my favorite games! I remember playing it at that stutter speed on my original XT on a CGA 4-color graphics card… Honestly, the PC was a bit overwhelmed. I found the game to run too slow. But I was a kid, I didn’t mind. Practices patience :)
Fantastic project!
Original V20, dedicated SRAM chip instead of relying on FPGA connected SDRAM (32MB, at least 50MHz random access capable), original Yamaha YM3014 DAC, original ps2 peripherals, cool transparent case. Can tell lots of fun and love went into it!
One thing Im not a fan of is that Chinese icesugar-pro FPGA board with its terrible pinout https://github.com/wuxx/icesugar-pro/tree/master/schematic Diagram has all the important bits and parts quality is fine, but it had to be routed by a student :| who didnt understand why fast bus connectors for the last ?40 years now? have all those ground pins interspersed with signals. Someone took DDR2 connector, looked at it and said “LOL lamers put so many grounds looks ugly” then proceeded cramming all ~100 signals together with just 9 grounds while leaving 64 unused pins on the sides. As a devboard its terrible. I would even argue its marginal here in its current overclocked to 20MHz form.