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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 11th May 2021, 7:49 pm   #1
mole42uk
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Default 80-BUS Loft treasure?

I was in my loft today sorting out several boxes of old Apple Macintosh stuff (printers, Trinitron monitors, a couple of SE computers, interfaces, keyboards) when I found a box containing several foil-wrapped 80-BUS items:

1. GM812 IVC board
2. MAP80 256k RAM board
3. GM813 Z80 CPU board
4. GM829 FDC/ SASI board
5. DIY EPROM Programmer board
6. Xebec disk controller
7. Shugart 604 5Mb hard drive
8. TEC FB-504 720kb floppy drive
9. A 4U rack-mount case containing a heavy-duty power supply
10. NASCOM 2 CPU board
And varous cables, NASCOM keyboards etc....

I do have most of the user manuals to go with but I have no idea what to do with it all. Any ideas would be most welcome!
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Old 11th May 2021, 8:27 pm   #2
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Default Re: 80-BUS Loft treasure?

Give it all to me Or alternatively rebuild a Gemini and extend one of the top three threads in this corner and enjoy the 70's experience...
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Old 11th May 2021, 8:35 pm   #3
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Default Re: 80-BUS Loft treasure?

Tim just beat me to the obvious answer almost everyone is going to give.

I think you have two projects there, try and get the Nascom running again, then also get the rest running cpm.
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Old 11th May 2021, 8:53 pm   #4
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Default Re: 80-BUS Loft treasure?

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Originally Posted by Mark1960 View Post
Tim just beat me to the obvious answer almost everyone is going to give.

I think you have two projects there, try and get the Nascom running again, then also get the rest running cpm.
There was a CP/M Gemini system at one time, a lot of my floppies have clues on the labels which probably also used the hard drive....and I started with a tape-based NASCOM 2 so I probably have most if that somewhere in the loft.

I do remember an 8" (yes, eight inch) hard drive which dimmed the house lights when I started it, but I don't have that anymore.
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Old 11th May 2021, 9:23 pm   #5
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Default Re: 80-BUS Loft treasure?

Indeed - we will all enjoy living vicariously as you nurse them back into functioning machines.
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Old 16th May 2021, 3:01 pm   #6
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Default Re: 80-BUS Loft treasure?

I have 2 of those TEC FB-504 FDDs in a Cumana dual unit, one reads discs only, the other nothing, no read or write.

While searching on the internet for info. I came across a report of leaky caps causing all sorts of corrosion problems on these drives.

A look at mine shows both have many leaking black electrolytics so yours probably will be affected as well!

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Old 16th May 2021, 7:21 pm   #7
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Default Re: 80-BUS Loft treasure?

Quote:
Originally Posted by MeerKat View Post
I have 2 of those TEC FB-504 FDDs <snip> leaky caps causing all sorts of corrosion problems on these drives.
A visual inspection this evening doesn't reveal anything to worry about! There are four electrolytics, none of which seem to be leaking.... An electrical test will happen in a few days.....
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Old 16th May 2021, 9:28 pm   #8
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Default Re: 80-BUS Loft treasure?

In that case there must be a bad batch in the field and I have two of them, the S/Ns on mine are 0540040 42664 & 0540040 42670, 6 apart. The corrosion in mine from 4 leaking caps has open circuited some of the tracks.

Just looked on ebay and a guy in the US has 8 new ones for sale and the S/N on the one pictured is 0540040 42672, only 2 away from one of mine, must be old stock. I'll drop the guy a note, may save him some grief!

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Last edited by MeerKat; 16th May 2021 at 9:46 pm. Reason: Added more detail
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Old 17th May 2021, 4:29 pm   #9
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Default Re: 80-BUS Loft treasure?

Hi Richard,

I would be interested to know if your drive works, please let me know after your test and also what the S/N is.

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Old 17th May 2021, 5:35 pm   #10
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Default Re: 80-BUS Loft treasure?

My serials are 540040-10137 and 540040-10184. They are both half-height drives.
The 8 drives I saw on ebay were all full-height I think.

I'll try and do a test this evening if my old XP machine will recognise them.
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Old 18th May 2021, 7:23 pm   #11
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Default Re: 80-BUS Loft treasure?

Quote:
Originally Posted by mole42uk View Post
I was in my loft today sorting out several boxes of old Apple Macintosh stuff (printers, Trinitron monitors, a couple of SE computers, interfaces, keyboards) when I found a box containing several foil-wrapped 80-BUS items:

1. GM812 IVC board
2. MAP80 256k RAM board
3. GM813 Z80 CPU board
4. GM829 FDC/ SASI board
5. DIY EPROM Programmer board
6. Xebec disk controller
7. Shugart 604 5Mb hard drive
8. TEC FB-504 720kb floppy drive
9. A 4U rack-mount case containing a heavy-duty power supply
10. NASCOM 2 CPU board
And varous cables, NASCOM keyboards etc....

I do have most of the user manuals to go with but I have no idea what to do with it all. Any ideas would be most welcome!
would be good to see some photos
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Old 19th May 2021, 5:11 am   #12
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Default Re: 80-BUS Loft treasure?

First results are mixed- the XP machine sees the drives as 3 jobbies even after Id altered the BIOS. The drives spin up okay but the machine asks me to insert a disk.

I brink Ill now finish off the Fluxengine that Ive bought because that is supposed to cope with any floppy hardware.
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Old 19th May 2021, 11:44 am   #13
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Default Re: 80-BUS Loft treasure?

Jealous, I second the request for photos!
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Old 19th May 2021, 12:09 pm   #14
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Default Re: 80-BUS Loft treasure?

Quote:
Originally Posted by mole42uk View Post
First results are mixed- the XP machine sees the drives as 3” jobbies even after I’d altered the BIOS. The drives spin up okay but the machine asks me to insert a disk.

I brink I’ll now finish off the Fluxengine that I’ve bought because that is supposed to cope with any floppy hardware.

Is that because PC's never really used 5.25" 720KB drives? - The most common types being:

5.25" 40T D/S - using Double-Density for 360KB
3.5" 80T D/S - using Double-Density for 720KB
5.25" 80T D/S - using Hi-Density for 1.2MB (+supports lower Double-Density 360KB 40T discs, with double-stepping)
3.5" 80T D/S - using Quad-Density for 1.44MB (+supports lower Double-Density 720KB discs, with extra notch)

(However, some later BIOS's may only support 1.44MB and 1.2MB drives)

Although there shouldn't really be much difference on the electrical interface between 5.25" and 3.5" drives, so if BIOS is set for 720KB then should still work with a 5.25" 80T Double-density drive (or Maybe even a Hi-Density 1.2MB 5.25" one, as it will also support lower Double-density 720KB and also 40T 360KB with double-stepping by computer).

But if these TB-504 drives weren't from a PC, then might have ensure drive-select is set to 1 and cable has twist to use for A: drive
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Old 19th May 2021, 10:38 pm   #15
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Default Re: 80-BUS Loft treasure?

Thanks for the update on the drives Richard, the serials are a long way from mine so hopefully they are from a good batch, I hope you get them sorted.

I am just about to start re-capping my two... I'll post when done.

Regards,
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Old 20th May 2021, 5:56 am   #16
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Default Re: 80-BUS Loft treasure?

Quote:
Originally Posted by ortek_service View Post
Quote:
Originally Posted by mole42uk View Post
First results are mixed- the XP machine sees the drives as 3 jobbies even after Id altered the BIOS.
Is that because PC's never really used 5.25" 720KB drives? - The most common types being:

5.25" 40T D/S - using Double-Density for 360KB
5.25" 80T D/S - using Hi-Density for 1.2MB (+supports lower Double-Density 360KB 40T discs, with double-stepping)
<snip>
But if these TB-504 drives weren't from a PC, then might have ensure drive-select is set to 1 and cable has twist to use for A: drive
According to the User Manual these are 80 track double-density double-sided drives which are specified as 1Mb unformatted, 656kb formatted. Neither drive was originally used in a PC, both were from a CP/M system so they may just not be compatible with the rather limited hardware options from a Windows-based machine.

The XP sees them as 3 drives and spins the motor at the correct time, but fails to see that there's a disk inserted.
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Old 20th May 2021, 6:32 am   #17
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Default Re: 80-BUS Loft treasure?

From what I found here: http://www.mfarris.com/floppy/tec.html
(Although others seem to quote a different size) they were fairly standard 80T D/S drives, that could handle upto Double-density
- The exact formatted-capacity being very dependent upon how many / large the sectors per track are on the system they are being used with, and could be 400KB Single-density / 640KB on Acorn systems, to 720KB or more on others.

If they didn't come from a PC, then they may need to have Drive select links changed, as PC's always had 'DS1' fitted, and had a twist in the cable to make one on the end of the cable appear to controller as drive 0.
- It's possible that the motor may still spin-up on other drives not being accessed (it may be a selectable option link), - so it's whether the light on the front comes-on that's most important.
And also, if connecting 2 drives, may need to remove terminator resistors from one in the middle of the cable.
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Old 20th May 2021, 6:42 am   #18
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Default Re: 80-BUS Loft treasure?

I'm attaching the specification page from the user manual, seems to differ from my memory of the accepted capacity of floppies! I should think that techniques developed to get more data per disk than when the drives were originally made.
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File Type: pdf TEC FB-50x spec.pdf (124.4 KB, 11 views)
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Old 20th May 2021, 7:55 am   #19
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Default Re: 80-BUS Loft treasure?

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Originally Posted by ortek_service View Post
<snip> so it's whether the light on the front comes-on that's most important.
Yes, the light comes on when I (double) click on the disk icon and extinguishes when the systems asks me to insert a disk....
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Old 21st May 2021, 5:19 am   #20
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Default Re: 80-BUS Loft treasure?

Quote:
Originally Posted by mole42uk View Post
I'm attaching the specification page from the user manual, seems to differ from my memory of the accepted capacity of floppies! I should think that techniques developed to get more data per disk than when the drives were originally made.
Well their figures more or less add up, as they've specified that formatted capacity is using 16 (256-Byte) sectors per track = 4096 Bytes per track. So:

1 sides * 40 Tracks * 4096 = 163840 Bytes (160KiB) Spec: says 164KB
2 sides * 40 Tracks * 4096 = 327680 Bytes (320KiB) Spec: says 328KB
1 sides * 40 Tracks * 4096 = 327680 Bytes (320KiB) Spec: says 328KB
2 sides * 80 Tracks * 4096 = 655360 Bytes (640KiB) Spec: says 656KB

(So looks like they been using HDD definition of 1000 Bytes (1kB), rather than original 1024 Bytes (1KB, now 1KiB to save confusion) used for memory - as well as rounding-up)

Capacity using Double-density (MFM) on PC's 9 (512-Byte) sectors per track = 4608 Bytes per track. So:

2 sides * 40 Tracks * 4608 = 368640 Bytes (360KiB) (Original main 5.25" format)
2 sides * 80 Tracks * 4608 = 737280 Bytes (720KiB) (Original main 3.5" format)

PC Hi / Quad Density formats use higher (but different) number of 512Bytes sectors per track (15 for 1.2MB & 18 for 1.44MB)
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