Raspberry Pi Virtual Floppy for ISA (PC XT/AT) Computers
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- Опубліковано 23 сер 2024
- I was tired of carrying media back and forth to my homebuilt XT computer, so I used dual-ported RAM to build a virtual floppy replacement that serves floppy images up from a raspberry pi. A small BIOS extension loaded into the dual-ported RAM simulates a floppy disk drive. Requests are made by the ISA PC, and served by the raspberry pi. For more electronics projects, see www.smbaker.com/
This really tickles my ISA bus fascination, now devouring your blog!
Wow
I found solutions to many of the problems I had in my mind. You are a gold mine for solutions.
Thank you.
Greetings from north Africa ;(Algeria)
Just discovered this today, this is one cool project!
That's pretty cool. The only thing I could think to improve it would be an option to have it run as the B drive so you could make images of floppies with it.
ISA: loved by developers and engineers for its simplicity, hated by users for its simplicity.
Actually ISA live almost forever via IDE.
@@CarlosOsuna1970 still in modern PCs as the LPC bus, which connects things like the SuperIO chip and sensors.
Yay! New video. Just ordered three of your RC2014 bus monitor cards. Looking forward to putting it together! Kudos sir, your videos and blog are massive learning resources for me.
The level of your genius is unparalleled.
Cool! I built an 8085 SBC that uses a Pi for storage as well, for CP/M development. Never thought of doing the same thing for a DOS machine.
I really wish I could thumb this video and your site up multiple times.....This is *exactly* what I want to do on my Tandy 1000TX, so I'm hoping more info appears on your blog for me to digest and replicate! Thank you for posting this, as I've always thought what I wanted to do was impossible
These a great video's exactly the things i like...
Scott, great stuff. Some fantastic ideas in this video for my own projects. Appreciated!
Are you planning on adding the details to your blog? This is an amazing concept, I'd like to build one of these to play with. Wonder how hard it would be to modify it to emulate a cd-rom for a pentium class system.
awesome video! I wish i had as much as 25% of your knowledge... hardware and software nice!
Keep up the good work. thank you for this video.
Very cool!
very cool stuff
As far as I remember, NE2000 compatible network cards have an 8-bit ISA mode. The Atari ST guys utilize that to have cheap(ish) network on the ST.
yes they are all over the place even I have a few of them
I'd really love to see a Motorola 68k processor on an ISA board, should be a fun CPU on a card.
Your 8-Bit SDCard adapter includes software in the BIOS to boot the machine from the serial port, or mount floppy images too! I don't know why you never build up the serial ports on your cards. I built the one on the Floppy adapter, and it works great with this, or with Laplink.
there is a follow-up video where he takes the board from prototype to gold edge showing how to upload the zipped gerbers to JLPCB (this video is the original "green board" review), and on _both_ those "release" revision boards, the serial port is indeed wired up.
Neat! I hope to have my actual IBM 5160 up and running soon. Finally got a Model M keyboard, but the video card is faulty :(
How about hooking RPI0 directly as a floppy drive? Should work more transparent.
On the other end you can make wi-fi samba share with images and a txt file with configurations to change them on-the-fly though.
Way too late but you can do logic level conversions on the cheap with a transistor and two resistors. Alternatively, sparkfun sells a board with four such arrangements each. Part is BOB-12009. I've got a bunch, they're handy.
Hi, so I have the same setup. Question... The VGA card shows 512kb on boot but with Check it, it only shows 128kb. Is that a limitation of the 8088 or something I did wrong. I did set it up to use the extra hi mem and that works, if course with the proper software. Maybe that is stopping the extra video ram. I not sure I would even notice the difference but if I can use it I would like to.
Love your videos sir!!
Try to run Minix 1 or 2 on your computer.
The old Minix is a free unix for 8086 compatible pc.
Version 3 is rewritten from scratch and not compatible.
There's also Microsoft's Xenix, although it might need a 286. Various flavors of CP/M, USPC P-system, Plan-9, GEM. These and many more OS are available at Winworldpc.com There was also an attempt to squeeze as much of linux as possible on a 8086 in a project called ELKS.
But you still need to perform the task of removing the micro-sd and inserting into to your desktop pc in order to transfer the files over. How much quicker is this than removing the cf card when the micro-sd card is fiddly and easily damaged plus it is located inside the case ? The ISA card is still a great project but does not solve the problem that you started out with. Now if you used an pi with wifi then that would have been a much more of a solution.
rather than hooking it up to the ISA bus cant you directly fix it to the floppy connector on the mother board ?? just curios
This chip is expensive. I am in high school and just can't get some luck with this.
Edit:
Was looking on mouser for the chip and all I could find were high priced chips.
Nice! but you skipped the software dev part 🧐 would have been nice to see that too!
Would 10base2 network work? These were made in ISA format.
What values are you using for the resistor package (RN1)? It's not specified in the schematic, unlike the other resistors.
Goodjob
Is there a reason you couldn’t have made this a b: drive so you didn’t have to clobber your floppy?
Awesome video, Scott!
Could you elaborate how you installed the int 13 handler from the section of SRAM?
How does the BIOS know where to look for it?
The BIOS automatically scans high memory looking for blocks of memory that begin with the bytes 0x55, 0xAA. If it finds one, then the third byte is assumed to be a length, and it then computes a checksum to verify that a valid extension is present. Assuming everything checks out, the BIOS will jump into it and run it. So in this case, all I had to do was to make sure the first 512 bytes of the dual-port RAM contained the appropriate header bytes and checksum. It was a bit of work fitting everything I needed into such a small space though.
Hmm, couldn't that mess with memory mapped I/O too, though?
Interesting, I assumed something like this, but I didn't consider it to be too reasonable, as scanning the entire memory would take some time,
but I guess if it just scans a specific high region, it won't take that long.
I see in bios mode you drop down to a buffer size of 256 bytes, does this have much impact on performance?
This could be upgraded with Wifi or network filesystem :-)
Why not use a Gotek with FlashFloppy firmware? It is cheaper than a Raspberry Pi.
Cheaper than a $35 RPi 4, but not a Raspberry Pi Zero which is $5-10
Scott, you make it too easy.
There easier way. EBay has 8 bit ISA net cards. You can connect a XT computer to a file sharing network, I used file sharing on an XT pc when I was at University. Don't know how to set it up.
They are unbelievably slow. Not much faster than Laplink over a serial cable.
@@squirlmy For an XT computer, it's plenty fast. For today computer, 10Mbs is too slow.
Can you make a Mp3 player? The idea is to send commands from the ISA computer to the Pi and select which file to play. Then we need to add the hardware for the audio output as the Pi Zero does not have it by default. What do you think? I think it will be a great project that does not require too much extra effort and we will all be able to listen to music on our vintage computers :) There are already some serial mp3 players, but they do not allow retrieving the list of songs for example.
But, why would you put it inside a PC instead of just having the Raspberry Pi with USB speakers outside of the PC??? The quality of speakers available is much, much better than tinny PC speakers of the original PC, XT, AT or clones. Then you can take it away with you in your pocket. You have a great solution, you just need a better problem to solve! lol! It's also probably possible to create a Video Card of sorts for the old PCs with a Raspberry Pi, too, so you could use HDMI. Another thing that's an issue for the vintage PC collectors, is that even the weakest RPi is many times faster and more powerful than the PC itself. You can emulate a 8088 or 8086 PC with all the extras within the Pi easily. So the PC has nothing to do. You may have seem some Amigas that are just the Raspberry Pi inside an Amiga shell, emulating the Amiga without any original circuitry. You could do the same with an empty PC case with a power source for the Pi, that would be more sensible than trying to use all the obsolete unneeded PC components.
Now need something like this for IDE CDROM emulation.
Why? there's not a lot of practicality over using virtual ISOs on a hard drive or XT-IDE Compact Flash 8-bit adapter (CF uses IDE). For XT and ATs (8088 and 8086 CPUs), which only run DOS 1 to 3.x, the maximum addressable sectors on a disk was 4096, each sector could contain 4K or 4096 bytes, which adds up to a potential total of 16 MEGABYTES. Getting a 386 with the DOS 386EMM.SYS memory manager gets through all these limits, but consider this history: MS/PC-DOS 4+ was needed to have a storage medium of over 32MB, and DOS 5, to get over 512MB. FreeDOS gets around these limits, and old DR-DOS had some memory tricks, I forget the details. Looking at the original BIOS, he original BIOS INT 13h interface allows for 1024 cylinders, 256 heads, and 63 sectors per track. A PC using INT 13h can therefore only access 504MB. Anyways, whether using XT-IDE with Compact Flash, or just an old hard drive, there's little advantage to be gained over ISO files put on those mediums. The biggest issue is probably getting around elaborate copy-protection schemes on some CD-ROMs, but I think that was mostly Windows era games. And, all those DOS games previously worked within those limits, so they are small. Much smaller than modern games.
My original answer mainly deals with vintage computers. But even for Windows games for Pentiums and above, there's no advantage of hardware emulating a CD or DVD, rather than on a drive. Any MP3s and movie clips perform better and can be compressed on a hard drive or emulated hard drive. Optical drives sucked.
how do you get the graphics in the terminal?
it's KVM
its kinda funny that the pi zero has more power under the hood than the XT..