Semi-Virtual Diskette (SVD)

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Sep 24'07  -  Aug 28'06   -  Jun 12'06   -  Jan 22'06   -  Jan 4,'06   -  Oct 16'05   -  Jun 23'05   -  Aug 21'04   -  May 22'04   -  Apr 18'04   -  Apr 06'04   -  Feb 1'04

September 24, 2007


It has been over a year since I've done ANY SVD-oriented stuff. I tell you, I had the best of intentions. I was taking a break from shipments so I could concentrate on doing the SVD 2 (or II or ][ for you Apple fans). How was I to know what was going to come my way?

Without getting into too many gory details, I've switched jobs. I don't advertise it too much, but I'm in venture capital and we have started a new fund "Guggenheim Venture Partners." Yes, it's associated with THAT Guggenheim. I just got back from a trip to Europe and Scandinavia where, among other things, I hosted a reception at the Guggenheim Berlin museum. Suffice it to say, I have been concentrating on work for the last year. Well, work and one other thing...

Last fall my wife signed me up for Science Day for my son's school. For this "Science Day" I had to come up with something to teach the kiddos. Naturally, it was something electronic. If you're curious, take a look at the RetroGame. It was fun, and the kids loved it...though it took more time than I had.

On to the GOOD news. I'm back into vintage collecting and that means SVD2! (I'm actually starting to like "SVD ][" - what do you think?) Here's my plan:

  • I'm combing through all of the e-mail that landed in my SVD mailbox. I'll be responding to everything as quickly as I can. It is really full and I sincerely apologize for not getting back to all of you sooner. :-( And I'll attempt to make it up to you.
  • SVD ][ design is in full swing. Here are some of the features:
    • Minimal hardware design - I don't mean to say that the hardware is smaller than the SVD 1 - actually it is bigger and more complicated. However, the hardware is designed to be static. New floppy support can easily be added without changing the hardware. This was a mistake I made with the SVD 1...most new formats had to be programmed in the firmware on the SVD 1 board itself. The SVD ][ will still have static firmware.
    • USB-oriented - the SVD itself has very little memory. All disk images are served from the host "modern" computer with a 12M USB link. This gives me a track-transfer-time of about 80ms. With some judicious caching, this is good enough to keep vintage hardware happy while moving the heads around. The point here is that you can have images of ANY size!
    • USB-oriented #2 - I am intending to support USB memory devices as well. This is for those of you who don't have a modern computer next to your vintage box. You can simply write the images to a USB-drive, and the SVD will use those images. This feature is second in line behind the USB-connected mechanism.
    • Support for nearly ALL formats of floppies. I've change the SVD to model a physical floppy (somewhat) removing the need to emulate particular formats. Write precompensation is a pain in the (bleep), however, so certain restrictions and allowances have to put in place. Suffice it to say, I haven't found a format that it can't handle (that is, formats before 1990 or so).
    • Built-in termination.
    • Doubled sided floppies (you hear that TI 99/4a fans??!!).
    • Apple half-track images will be supported. HOWEVER, I've never seen a half-track image. Anyone have one out there?
    • 2μs (micro-second) bit cells. This supports up to 500Kb transfer rates. I may be supporting 1us bit cells, but I doubt it. 500Kb should work for damn-near everything (again up to 1990 or so).
    • Minimal external interface for different vintage hardware. The "Apple adapter" now turns into a simple PCB with no parts. Except, I'll probably still put the head-seeking phase LEDs on the PCB...those are just too cool. Most adapters will have a simple PCB with not parts.
    • 4 simultaneous floppies will be supported. I wrestled with the idea of going up to 16, but very few controllers supported that many floopies, so I just went with 4.
    If you have any feedback on what you'd like to see in SVD ][ please let me know.
  • SVD ][ development is going well. I expect to spin a PCB within a couple of weeks. It won't work completely I'm sure, so I'll need another one. The software is going to change substantially. All-in-all, MAYBE I'll be done by the end of the year. At the least I'll need some help testing.
  • I have 4 SVD 1's laying around, and 4 apple adapters. I'm going to e-mail back those people who were looking for SVD's and see if they're still interested. I'm NOT going to make any more SVD 1's. It is a nice little device that served it's purpose...but it's big brother is going to take over.
  • Once the SVD ][ works, I intend to make a BIG construction run. I may even work with someone to build the things. Hopefully we'll keep the price nice and low! Right now, I don't see the price being any higher than it was before.
I'm sure I'm missing something, but I wanted to update you all. Please e-mail me if you are still interested in the SVD 1, although I'll contact you if I can find your previous e-mail. Also, please e-mail if you have SVD ][ suggestions or feedback.


August 28, 2006


Unfortunately, I'm suspending shipments of the SVD...but just for now. It's great to have all of the interest in the SVD, for sure. However, it's been very difficult keeping up with the orders. As you may know, I build these things opposed to having them manufactured.

So, I am suspending shipments for any new orders. For those of you who already have orders in, I'll be getting shipments out very soon. You'll be individually contacted.

HOWEVER, feel free to put in orders if you'd like to get on the list for when I resume shipments! Also, it will help me keep you posted with the status of the SVD.

So, what will I do with all of the "extra" time I have? Work on the SVD II (actually SVD 1.5) is in full swing. Watch this space for more detail.


June 12, 2006

Hello! Some of you are probably surprised to hear from me here...

I've survived the perfect storm of tons of travel, switch to a new job (e-mail offline if you are interested), and a major personal system upgrade. Still Linux, but bigger faster machine with a Terastation behind it. All of these things are good me.

So here's the issues:

  • I've fallen way behind on filling SVD orders. (no kidding...)
  • I've dropped a few order e-mails...I know I've seen them, but I can recover them from any system I can find.
So, PLEASE, if you don't hear from me within the next couple of days, please assume that I dropped your order e-mail and try again. Note that I have 6 -- count-em SIX! -- SVD's that are ready to be shipped out. They'll go fast, so let me know!

VERY  sorry for any problems this may have caused you all.


January 22, 2006

I've had a few airplane trips in the last couple of weeks and used the time very productively. I've completed the Apple file writing tools!

Here are the details:

  • The two helper tools tosvd and fstool have been updated with the ability to write NIB, DO, and PO format files.
  • The graphical interface (the SVD Control Program) will automatically recognize the new capabilities of the helper tools and present the new write formats as options when saving a file image. So you don't need to update the SVD Control Program.
  • I'm not ready to issue a complete new software distribution yet, but I thought I'd make it possible to at least save images in the popular Apple formats. So to install this new capability you simply install the two helper files. See the Download Section for information.
  • You can use the new write capablities to convert from one format to another, too. Simply load a floppy image, then immediately save it in a new format. NOTE:The programs will do their best to perform the conversion for you. However, if you try to write a NIB image in DO format, it may or MAY NOT work. DO format can only be created from images from which standard sector data can be extracted. Copy-protected images, for example, often cannot be converted as such.

Note that I've also update the Apple instruction pages with notes about writing. These are important notes to read, particularly if you are using the SVD to backup real floppy images, uploading them to the PC.

January 4, 2006

Just a quick update at the beginning of the year to detail the way in which you can connect the SVD to an Apple //c. Please see the new Apple //c Page.

October 16, 2005

You're not going to believe this, but Apple ][ "write" works! I figure everyone was giving up on me...but finally, after a hectic summer and finally finding some time for my "hobby" I have completed firmware support for the Apple write.

So what is "Apple ][ write?" Basically it is the ability for you not only to run programs from the SVD, but also to copy disks and files to the SVD. This lets you do things such as make backup copies of your diskettes, or simply to play games that write the disk drive. Then you can then transfer the image to your PC for archival or running on your favorite Apple emulator.

Here are the details of Apple ][ write support:

  • Firmware version 2.4 contains the new Apple ][ "write" support.

  • v2.4 includes support for both NIB and GCR6x2 write. Practically, however, there's little difference between the two. The NIB support is used for copy-protected games and Dos 3.2 support, and GCR6x2 is used for everything else. The GCR6x2 image is a bit smaller, so it downloads quicker.

  • Unfortunately, using bit-copy programs for copying diskettes doesn't work most of the time. Most of these programs try to verify that the bit image is exactly the same as what it wrote. The SVD, however, changes the image just a bit, and that is usually enough to throw off bit copy programs.

  • Sector copy programs work just fine.

  • In a future version of the SVD (the so-called "SVD II") bit-copy will work. But that is a long time from now :-).

  • Although you can write to the SVD, and even upload the files to your PC, the PC software doesn't yet support writing images to DSK, PO, DO, or NIB formats yet. It will, but I was concentrating on getting the firmware right first. You can save the uploaded images in SVD format for now. When the new PC software is ready, you can easily convert the SVD files to Apple formats.

  • To get the Apple ][ write firmware please contact me. The new firmware is distributed as a new programmed PIC, and you simply replace the PIC in your current SVD with the new one. I'll ship you the new PIC for the cost of postage. Now that's a deal!

So why'd it take so darn long??? :-) Well, when the guys at Apple created the floppy disk support - for a nice historical account look here - they did it "on the cheap." They did two things of importance to the SVD:
  • Processor Clocked Transitions - the transitions on the floppy were timed relative to the Apple ][ processor clock. And this translated to 3.911 µs bit cell widths. As if that weren't enough, every 65 processor cycles the Apple architecture would "hold off" to allow syncronization, creating a particular bit cell which was 4.1 µs wide. Suffice it to say, keeping in sync with the Apple disk transitions was a bit tough. I ended up implementing an "edge detector" in the firmware that will occasionally back-up a bit, allowing the SVD to stay in sync.
  • Read one way, write another - A rather annoying thing in the Apple disk architecture is that when the processor reads from the disk, it expects "pulses" indicating zeros and ones...much like any other floppy of the day. However, when writing to the disk, it generates a "flux transition" signal which directly drives the write head. This signal changes polarity whenever a one is to be written. It's really not too hard to implement, just different from anything else.

June 23, 2005

It's been along time since there's been an SVD web-site update. Sorry about that. The SVD, however, is moving forward quickly. Here's the latest:

  • The web site has been completely revamped. It is now completely PHP oriented, making it more consistent and easy to maintain. This means that I'll be able to update it more easily.

  • Apple ][ support is complete! Well...almost complete. You can get it, but it doesn't allow you to write to virtual Apple disks yet. :-( You can boot from the SVD, and you can play games, even many copy-protected ones. For more info about the Apple support, see Supported Hardware. Or go directly to the Apple-specific pages here.

  • TI99/4a support has begun. To be honest, it wasn't hard. The SVD supports the Western Digital controller already, it was just a matter of supporting the floppy structure and image encoding mechanisms. However, double-sided images aren't yet supported. Unfortunately, there are MANY DS SD images out there. It makes using the SVD with the TI99/4a somewhat problematic. Also, the TI99/4a file-systemisn't yet supported. This means that you can't download single files...yet.

  • The firmware has been upgraded to version 2.3. This version includes all of the above plus a few other important fixes. The most recent is a(nother) fix to write-precompensation problems found with the FD-501 for the CoCo (thanks Darren!). If you have any previous version, and would like to upgrade, please contact me.

  • The alternative TRS-80 Model IV Micro-mainframe controller is still not supported. It uses write pulses which are 250ns wide, just below the consistent detection limit of the SVD.

  • With this update, and at long last, I also release the source code for the firmware v2.3, SVD CP GUI v2.2, and helper applications v2.2.

  • Please take special note of the new trouble-shootingsections. Should help quite a bit.

  • Finally, my apologies for some of the non-completed sections on this web-site. I'll do my best to get them done.

August 21, 2004

  • At long last, you can now WRITE to the SVD! This means that in addition to booting and reading from the SVD, you can now copy files to the SVD and upload and save them. For example, if you have a data disk that you'd like to save on your PC, (1) download a blank floppy to the SVD, (2) copy the data disk from a real drive to the SVD, (3) upload the new image from the SVD, and (4) save it!. Note that for write capability, a new load of firmware is necessary as well as new software (both version 2.0).

  • The new version 2.0 SVD-CP (control program for the PC) is now available. This version adds support for the new write capability, upload and save, and a new set of helpful "tips". This version is necessary for the new write firmware version 2.0.

  • With the completion of the write capability, I will be releasing the firmware source code. With luck, I'll also release the SVD-CP source code and the help applications source code.

May 22, 2004

  • The Linux version of the SVD control program is now available! As always, it is really in Beta release in that I haven't tested everything. Please feel free to download and try it! It will be important to read the Linux installation notes on the download page! Click on the "PC Applications" on the left to go to the download page.

  • The new version 1.7 of the SVD control program is now available. This is the version that was expressly created for Linux, but I went ahead and released the Windows version too. There are a few bug fixes that Heathkit H8/H89 users will want to have. Click on the "PC Applications" on the left to go to the download page.

  • If you've ever wondered what the tosvd and fstool programs do, you're in least a bit of luck. Included with 1.7 is the html man page for tosvd. For you Linux guys out there (like me) I apologize for not releasing the man page version of tosvd first.

April 18, 2004

  • The SVD control program, which I am now calling SVD-CP (creative huh?) version 1.6 is now available! It is really in Beta release in that I haven't tested everything. Please feel free to download and try it! Click on the "PC Applications" on the left to go to the download page.

April 6, 2004

  • BREAKING NEWS - support for the TRS-80 CoCo has been created! It will be available in version 1.6 of the software. No hardware changes were necessary for this support.

  • Also in 1.6, the CP/M filesystem will be supported for both the Model IV and the H8/H89. "Filesystem support" means that you can add single files for a disk image instead of having to find a complete disk image. This makes it easy to grab a single CP/M program and run it.

  • 1.6 will include support for the HDOS filesystem for the H8/H89.

February 1, 2004

  • You may have noticed that the web site had changed quite a bit.  Yup, we've had a complete reorganization!  Hope you like it.  Please sign the Guestbook!

  • The name of this site has dropped the "TRS-80" reference.  This is NOT because of dropped support for the contrary, the SVD now supports more machines than just the TRS-80.

  • Version 1.5  is complete!  With v1.5 (both hardware and software) double density is now supported.  So the SVD works with the Model I, III, and IV.  This includes mixed floppy formats common on copy protected Model 1 games.

  • Floppy bus Termination is now included.  This means that you can easily use the SVD as the only floppy drive.

  • The Heathkit H8  is now supported as well.  You can boot your H8 directly from the SVD...although diskette images are rather tough to come by.

    Bad News - the SVD can no longer support (realistically) battery-powered operation.  It just takes too much juice to drive the old interfaces and run fast enough.

    Apple II support is now being developed. The plan is to use the same SVD, but with a small dongle to convert the appropriate signals.