Unusual issues with CP/M on H8/H89, H17, and VSG.

[Matthew Kiehl]

Hello,

I was hoping someone might shine some light on an issue I am experiencing.

I have been trying to get CP/M working with two disk drives, both connected to a VSG and I have tested this on both an H8, and an H89 connected to the same H17 dual drive enclosure with the same symptoms:

I can boot any of the various CP/M distributions (2.2 02, 03, and 04), but encounter a BDOS ERROR: SELECT message if I try to access drive B.

I noticed that if I wait for the motor on the first drive to stop, I can then access B:.  The issue with that is if I try to copy files or sysgen to another disk, it errors out immediately each time.  In addition, I have worked with multiple disks in HDOS without any issues.

I have also tried using MPI branded 5.25" drives over the original Wangco 82 drives with the same results.

I assume I must be doing something incorrectly, but still learning a lot regarding these computers.  If anyone has any advice it would be appreciated.

Thank you,

Matthew

[Joseph Travis]

Belt driven floppy disk drives don't work well/reliably with the VSG as there is too much jitter in the index signal to allow proper timing. Half height floppy disk drives that use a "pancake" motor tend to work much better.

Good luck!

Joe 

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[Matthew Kiehl]

Thank you for the response,  

I went ahead and rewrote the CP/M 2.2.04 disk with two half height double side drives connected, but if I boot from it, it boots to BDOS ERR ON A: SELECT.  If I continue, it will go to CP/M, likewise, if I wait for the motor to power down, I can go to B:, but otherwise if I try doing it while the motor is still running, I get the same error on B:.   I disconnected the second drive and ran CONFIGUR, and saved the settings with a single floppy and it will happily boot this way, but when I connect the second drive and rerun CONFIGUR, it will boot to the error on drive A.   Is there a possibility that I would need one VSG for each drive to use two disks?  

Matthew

[Joseph Travis]

One way to find out is to insert a cardboard "head protector" in the 'B' drive and try it.  It may be the index signal from drive 'B' is being seen on the buss even though it isn't being selected.

Joe

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[norberto.collado koyado.com]

Not sure but check if one drive has the termination. Also, do the drives have enough power?

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From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Joseph Travis <jtravi...@gmail.com>
Sent: Friday, April 24, 2026 10:57:55 AM
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Subject: Re: [sebhc] Unusual issues with CP/M on H8/H89, H17, and VSG.

 

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[Mark Garlanger]

I'm pretty sure one VSG is not going to work with 2 drives. Since it functions by using the index hole and uses that to generate the other 10 sector holes, I doubt it has time to resync to the new drive and get all the sector holes timed properly. I haven't used a VSG, so I'm not sure how it should be connected, or even if 2 VSG on the same controller would work. Maybe someone with more experience with these or if the developers of VSG are available, could help.

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[Jeff Tranter]

It does support multiple drives (up to three) monitoring the drive select lines and keeping track of the timing of each drive.

I use it with two drives.

See https://deramp.com/downloads/misc_hardware/virtual_sector_generator/VSG%20Manual.pdf

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[Eric Mack]

Complete Heathkit H8 Computer. Working, with Software and Peripherals & Modem | eBay

 

Due to declining health and a pending move, it’s time for me to pass my H8 system on to the next Heath enthusiast.

 

A big thank you to Norberto who helped me get the system running with his Dual CF card.

 

Please let me know what you think and share the link with others.

 

Eric Mack

[Eric Mack]

For reasons of health and a pending move, I've decided it's time to sell my HERO 2000 collection. See: https://www.ebay.com/itm/127828728082

[Santo Nucifora]

Hi Eric,

Is that software archived somewhere and if not, are you able to archive it before it sells?  I have a Hero 2000 but no software.

Thank you and good luck with your auction.

Santo

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[Scott Baker]

That's a very impressive collection, Eric. I'm going to utterly erase it from my brain though; I need the money in my bank account more than I need a third heathkit robot around the house! :D

Scott

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[Eric Mack]

Hi Santo, given the rapidly approaching move date and my health, I probably won’t be able to archive anything. I think Robert Doer has manuals and documentation and likely software. Otherwise, perhaps the next owner can help.

 

Eric

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