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View Full Version : Full demo video of the Altair FDC+ enhanced disk controller



deramp5113
June 20th, 2015, 08:07 AM
I've posted a video that demonstrates the FDC+ for the Altair operating with a number of different drive configurations. It's a long video, but you can scan for the black title pages that separate the different demonstrations to move things along a bit :)

https://youtu.be/1U013-9eB1A

Mike

JNZ
February 5th, 2016, 12:29 PM
I'm late to this party, but hopefully it's just given people time to use this board.

Is this board compatible with S-100 systems, or are there specific features that make it a product only for actual Altairs? I have an S-100 bus system with a Jade "Double D" double density disk controller that's currently configured to work with two 8" drives. The drives are too unreliable for me to use the system, however, and so far my efforts at debugging them have only let me conclude that it's something in the magnetic interface, which I don't know how to measure or fix. I'd like to avoid making the hardware (desoldering-required) modifications to this board that would let me use more reliable drives, such as 5 1/4" or 3.5".

Thus...would I be able to use this FDC+ board with 5 1/4" drives?

My ultimate goal would be to use my PC to write a disk image to a 5 1/4" disk and boot CP/M on my real system.

Soupwizard
February 5th, 2016, 02:32 PM
There are definitely new design S-100 floppy drive boards (and more) at http://www.s100computers.com/My%20System%20Index%20Page.htm , you buy the bare pcb and solder on the components.

JNZ
February 5th, 2016, 02:49 PM
There are definitely new design (you buy the bare pcb and solder together the components) general S-100 floppy drive (and more) at http://www.s100computers.com/My%20System%20Index%20Page.htm

Though I love S100 Computers.com (that's Herb's site, right?), I don't mind paying someone for an already assembled solution. Soldering is just a job to me, and if I can skip it it's all the better.

However, whatever solution I go for, I do have some common questions: is it feasible to write to the 5 1/4" disk from my PC in a format that the FDC will recognize? I imagine just using the Linux command dd and writing an image to it, but I don't know enough about the format to know what the FDC expects, let alone CP/M or the bootloader.

Soupwizard
February 5th, 2016, 03:00 PM
> is it feasible to write to the 5 1/4" disk from my PC in a format that the FDC will recognize?

IIRC, Dave Dunfield's ImageDisk should do what you need, thought it may require you to find an older PC with a supported floppy disk controller (or one with an ISA slot to put a floppy controller in). http://www.classiccmp.org/dunfield/img/index.htm

> Soldering is just a job to me, and if I can skip it it's all the better.

Ditto for me too, at first it seems like part of the adventure, but after 10 pins I'm like "ok... someone please take my money to assemble this board".

deramp5113
February 5th, 2016, 07:58 PM
Is this board compatible with S-100 systems, or are there specific features that make it a product only for actual Altairs?

This board will work in most any S-100 system with a 2-4 mhz processor, however, the software you'll find that works with this controller is going to be Altair specific. This includes Altair disk BASIC, Altair DOS, and CP/M for the Altair. All of this software requires a 2 mhz (no faster, no slower) CPU because of the way MITS designed their disk controller and their disk driver code. The other system requirement is an Altair 88-2SIO serial board, or a serial board that can be strapped to duplicate the receive and transmit ready flags of the 6850 ACIA used on the 2SIO (e.g., the SSM-IO4 will work).


Thus...would I be able to use this FDC+ board with 5 1/4" drives?

Yes, this board can work with 5.25" drives. If using an HD drive like the TEAC 55-GFR, the FDC+ can make the drive function identically to an 8" drive as far as the computer and software are concerned. You can also use a 5.25" drive as a 5.25" drive, but the amount of software available is substantially less and the capacity is only about 70K. (Altair's minidisk software was never updated after the 1st generation of SSSD, 35 track drives.)


My ultimate goal would be to use my PC to write a disk image to a 5 1/4" disk and boot CP/M on my real system.

This is a hard-sectored controller. You won't be able to write disks on a PC. However, it is very simple to transfer disk images over a serial port and have the S100 machine write the disk. This is possible on a "cold" machine that doesn't have any bootable OS working at all. For example, some compatible disk images and the disk transfer utility are on the deramp.com website (at http://deramp.com/downloads/index.php?dir=altair%2Fsoftware%2F8_inch_floppy%2F ).

Mike

MarsMan2020
February 7th, 2016, 07:10 PM
Though I love S100 Computers.com (that's Herb's site, right?), I don't mind paying someone for an already assembled solution. Soldering is just a job to me, and if I can skip it it's all the better.

However, whatever solution I go for, I do have some common questions: is it feasible to write to the 5 1/4" disk from my PC in a format that the FDC will recognize? I imagine just using the Linux command dd and writing an image to it, but I don't know enough about the format to know what the FDC expects, let alone CP/M or the bootloader.

I think the S100Computers board is your best bet. Easy to write the CP/M BIOS for it since it has its own onboard Z80 doing most of the heavy lifting. You can even use it with a standard 3.5" drive, which would be way easier to write images to from a modern PC.

jgalinat
February 8th, 2016, 07:43 AM
Though I love S100 Computers.com (that's Herb's site, right?)

No actually that is John Monahan's site. Herb's site is retrotechnology.com.

Regards,
Jeff

JNZ
February 8th, 2016, 09:19 AM
No actually that is John Monahan's site. Herb's site is retrotechnology.com.

Regards,
Jeff

Oh, I've met John...I think. Unless I'm very mistaken (and going just by his thumbnail picture) I think I sat next to him at Herb's S100 bus talk at VCF East last year. That talk got me into the idea that it was actually possible to own one of these computers today. I had thought they were all thousands of dollars and were too fragile to use reliably.

JNZ
February 8th, 2016, 09:23 AM
I think the S100Computers board is your best bet. Easy to write the CP/M BIOS for it since it has its own onboard Z80 doing most of the heavy lifting. You can even use it with a standard 3.5" drive, which would be way easier to write images to from a modern PC.

A 3.5" drive does sound appealing too, even if it's further away from the "original experience" of these computers (which is why I like the 5 1/4" solution too). It certainly would be convenient, however.

My current Jade "Double D" controller has a Z80A on there too, but it seems to require changing some discrete components to get it to work with the 5 1/4" drive...something I'd like to avoid doing for two reasons: it prevents me from repairing and using my 8" drives in the future, and it requires desoldering and soldering on a aged PCB.

I'll look into the S100 board and maybe the Versafloppy II, which new_castle_j has recommended and which looks pretty good.

JNZ
February 8th, 2016, 09:25 AM
This board will work in most any S-100 system with a 2-4 mhz processor, however, the software you'll find that works with this controller is going to be Altair specific. This includes Altair disk BASIC, Altair DOS, and CP/M for the Altair. All of this software requires a 2 mhz (no faster, no slower) CPU because of the way MITS designed their disk controller and their disk driver code. The other system requirement is an Altair 88-2SIO serial board, or a serial board that can be strapped to duplicate the receive and transmit ready flags of the 6850 ACIA used on the 2SIO (e.g., the SSM-IO4 will work).
...
This is a hard-sectored controller. You won't be able to write disks on a PC. However, it is very simple to transfer disk images over a serial port and have the S100 machine write the disk. This is possible on a "cold" machine that doesn't have any bootable OS working at all. For example, some compatible disk images and the disk transfer utility are on the deramp.com website (at http://deramp.com/downloads/index.php?dir=altair%2Fsoftware%2F8_inch_floppy%2F ).

Mike


Hmm, this does look rather interesting, and I've read through some of the PC2FLOP code. It is Altair specific in a way that I think would be an issue with my system, such that I think I'd have to rewrite it for at least the serial stuff (at a time when I'm trying to troubleshoot other things). It's a cool card, but since I'm not creating an Altair clone (so to speak), I should probably go with an S100-targeted solution.

smp
February 8th, 2016, 09:37 AM
I'll look into the S100 board and maybe the Versafloppy II, which new_castle_j has recommended and which looks pretty good.


I did not see the recommendation from new_castle_j at first glance, so I hope that I am not repeating what was suggested.

If you already have 8 inch floppy disk drives, I would strongly recommend the Versafloppy II. FYI, there is a great Versafloppy test program available on www.s100computers.com (John Monahan's site). I have run that test program with my two Versafloppy interface boards, and it is excellent tester.

Alas, all the CP/M BIOS code around all assumes 8 inch floppy disk drives, and I have only 5.25 inch drives, and I am not all that good at BIOS code changes, so I was not able to implement CP/M using my Versafloppy interface.

I ended up using the Northstar single density floppy interface first, since I already had experience with it long. long ago, and then I graduated to the Northstar double density floppy interface. I still have those Versafloppy interface boards, though. When someone makes some code or boot disks available, I'll be interested in trying it.

smp

JNZ
February 8th, 2016, 09:58 AM
I did not see the recommendation from new_castle_j at first glance, so I hope that I am not repeating what was suggested.

If you already have 8 inch floppy disk drives, I would strongly recommend the Versafloppy II. FYI, there is a great Versafloppy test program available on www.s100computers.com (John Monahan's site). I have run that test program with my two Versafloppy interface boards, and it is excellent tester.

Alas, all the CP/M BIOS code around all assumes 8 inch floppy disk drives, and I have only 5.25 inch drives, and I am not all that good at BIOS code changes, so I was not able to implement CP/M using my Versafloppy interface.

I ended up using the Northstar single density floppy interface first, since I already had experience with it long. long ago, and then I graduated to the Northstar double density floppy interface. I still have those Versafloppy interface boards, though. When someone makes some code or boot disks available, I'll be interested in trying it.

smp

He actually made the recommendation in an email thread with me.

The Versafloppy II looks good for my goal of using 5" drives, which are modern enough that I should be able to use them on a PC (I have enough of them laying around that I can put one in an old PC and use it to write data). There's one thing that greatly concerns me though...If I have IEE-696 compliant boards then the Versafloppy II will fail to handle a certain clock signal correctly, requiring messy modifications to the board, such as cutting traces and piggybacking a logic chip onto another one.

I don't know whether my main board or other boards meet this criteria or not.

As for CP/M, I intend to read the CP/M System Alteration Guide and see what parts of BDOS need to be modified to properly address the new floppy controller system calls. I don't know how difficult this is yet...

MarsMan2020
February 8th, 2016, 04:49 PM
A 3.5" drive does sound appealing too, even if it's further away from the "original experience" of these computers (which is why I like the 5 1/4" solution too). It certainly would be convenient, however.

My current Jade "Double D" controller has a Z80A on there too, but it seems to require changing some discrete components to get it to work with the 5 1/4" drive...something I'd like to avoid doing for two reasons: it prevents me from repairing and using my 8" drives in the future, and it requires desoldering and soldering on a aged PCB.

I'll look into the S100 board and maybe the Versafloppy II, which new_castle_j has recommended and which looks pretty good.

John's ZFDC board will work with 8", 5.25", and 3.5" soft-sector drives, up to 4 drives - so you can be as old-school or new school as you want. The example CP/M3 BIOS John has on his site is actually for 2x 8" and 1x 5.25" drives.

I have 2 ZFDC PCBs here waiting to get built, haven't gotten to them yet.

waltermixxx
May 26th, 2016, 06:21 AM
I'm in the process of building a small S100 system based on Josh Bensadon's new 8080 board, (just released, I should have it soon ) and Don Caprio's MINI IMSAI Front Panel. Josh's board is designed to either behave like an Altair main board or an IMSAI main board with built in 64K ram, eprom, and serial ports. It does have an SD card interface as well, but I think I would at some point like to have a real disk drive interface for it.

I know that IMSAI was stated to be an ALTAIR clone, but do you happen to know if your FDC+ board will work in an IMSAI? are the two similar enough? I'm hoping to run Josh's board in IMSAI mode, with an "IMSAI" front panel.

Links to boards mentioned:

http://www.s100computers.com/My%20System%20Pages/8080%20CPU%20Board/8080%20CPU%20Board.htm

http://www.s100computers.com/My%20System%20Pages/Mini%20FP%20Board/Mini%20FP%20Board.htm


P.S. still enjoying my Altair Clone purchased pretty much a year ago. :) I built a briel pocket term on a propeller proto board i had hanging around and it's a very nice system indeed. :) Josh checked it out, and was very impressed with it...(he is a die hard S100 bus guy!). :)

cheers. :)

cheers.

deramp5113
May 26th, 2016, 05:21 PM
I know that IMSAI was stated to be an ALTAIR clone, but do you happen to know if your FDC+ board will work in an IMSAI? are the two similar enough? I'm hoping to run Josh's board in IMSAI mode, with an "IMSAI" front panel.

This board will work in most any S-100 system with a 2-4 mhz processor. Software you'll find that works with this controller includes Altair disk BASIC, Altair DOS, and CP/M for the Altair. All of this software requires a 2 mhz (no faster, no slower) CPU because of the way MITS designed their disk controller and their disk driver code. Most Altair software also expect a MITS 88-2SIO serial board (or a serial board that can be strapped to duplicate the receive and transmit ready flags of the 6850 ACIA used on the 2SIO like the SSM-IO4).

Mike