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DOS-based Dynamic Drive Overlay disk (was: SERIOUS need of)

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leeb

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a DOS-based GENERIC
Dynamic Drive Overlay disk that will work on an IBM 810mb drive.

Why?

Im trying to put a size 14 foot (HD) into a size 8 shoe (V20-based laptop... specifically my Tandy 1500HD).

It comes with a Conner CP-2024 drive (615/4/17) and it balks at the IBM otherwise...

There IS a possibility that it might not work EVEN WITH the overlay, but currently this is the only option I can think of that SHOULD work...

ANY assistance would be appreciated!
:nervous:
 
Wouldn't ya know it...

NOW that Ive formally asked for help, I FIND ONE!!!

I am beginning to fear, tho, that the DDO may not run on a machine this old. I believe this because the install software wont boot.
SO...

I may have to be happy with the 20mb.

We'll just have 2c! :D
 
Is it really an IBM drive (not Hitachi or Fujitsu)?
Which model?
Which DDO did you try to use?

They did indeed often assume a 286 minimum.
 
What do you need more than 20MB for on a machine that old? XTIDE is an option, btw, assuming you have ISA slots.
 
MikeS said:
Is it really an IBM drive (not Hitachi or Fujitsu)?
Which model?
Which DDO did you try to use?
They did indeed often assume a 286 minimum.
Click to expand...

Well, it is an IBM drive but is made bi Hitachi... It looks 2b compatible tho. (The DDO came from IBM)

Raven said:
What do you need more than 20MB for on a machine that old? XTIDE is an option, btw, assuming you have ISA slots.
Click to expand...

1) You NEVER know when a 20mb will become too small, and
2) The 20mb had 2b 'fixed' and is likely to go down in the near future. Why NOT replace it with something bigger (presuming it CAN)?
 
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Well, it appears that I may be forced to accept the 20mb until it dies...
Or I am able to modify the BIOS ROM to be more 'flexible'...
 
Stay away from BIOS mods, unless you get a whole different chip for it and keep the original safe. Trust me, or you'll regret it if something goes wrong.
 
leeb said:
Well, it appears that I may be forced to accept the 20mb until it dies...
Or I am able to modify the BIOS ROM to be more 'flexible'...
Click to expand...

If you just change the drive table and re-calculate the ROM checksum, you should be fine. Like Raven says, though, save the image of your original ROM.
 
Raven said:
Stay away from BIOS mods, unless you get a whole different chip for it and keep the original safe. Trust me, or you'll regret it if something goes wrong.
Click to expand...

Fear not!!

I learned LONG AGO...


NEVER break something unless you have the parts to fix it again!
 
It took me maybe a dozen dead machines to learn that, by the way. *embarassed*

I refuse to let this little BookPC die though, the latest casualty. I ordered 10 BIOS chips to try writing to for it! lol xD
 
If you're determined enough, it's amazing what can be repaired. I bricked a Tandberg TDC4220 SCSI QIC drive--the Tandberg web site wasn't very specific as to what revision of the firmware would go with what revision drive and the bleeding flash utility burned the image anyway. Instant useless drive--with a SMT soldered-on PROM. I removed the chip using Chip-Quick and replaced it with a PLCC socket, reprogrammed the original chip on my PROM programmer and stuck it back in. Worked wonderfully.

The guy who runs the Coreboot web site recommends that you socket the BIOS chip on your motherboard if it's not that way already. Not a bad idea.
 
leeb said:
a DOS-based GENERIC
Dynamic Drive Overlay disk that will work on an IBM 810mb drive.

Why?

Im trying to put a size 14 foot (HD) into a size 8 shoe (V20-based laptop... specifically my Tandy 1500HD).

It comes with a Conner CP-2024 drive (615/4/17) and it balks at the IBM otherwise...

There IS a possibility that it might not work EVEN WITH the overlay, but currently this is the only option I can think of that SHOULD work...

ANY assistance would be appreciated!
:nervous:
Click to expand...

As far as I've ever heard/known, the early (XT class) Tandy HD laptops (1110HD, 1500HD, etc) use XT IDE hard drives, same as their later model XT class Tandy 1000 desktops, except the laptops use 2.5" versions.
Desktop XT IDE drives were uncommon enough (and only available in 20 and 40MB versions) - laptop XT IDE drives are even less common. The Conner CP-2024 the only XT IDE 2.5" HD I've ever heard of, but I'm far from being an expert on the subject.
Unfortunately, with this being the case, a drive overlay is not going to help you, because the drive is not electrically or logically compatible with the laptop.

What I would love is a XT IDE -> AT IDE converter, first for my Tandy 1000 desktops, but also for my Tandy 1110HD with a dead HD.
Is a project like that within the capabilities of anyone in this forum?

The information above is the best of my knowledge, but someone else may know better.

__
Trevor
 
Lord Moz said:
What I would love is a XT IDE -> AT IDE converter, first for my Tandy 1000 desktops, but also for my Tandy 1110HD with a dead HD.
Is a project like that within the capabilities of anyone in this forum?
Click to expand...

It's doable (translate one 16-bit DMA cycle to 2 8-bit ones), but it would be a fair amount of work for not much return (who else would use it)?

You might be far better off in the long run by employing an IDE-to-CF adapter and then using either a CF card or a Microdrive in that. Both can support 8-bit DMA, unlike the overwhelming mass of IDE hard drives.
 
Chuck(G) said:
It's doable (translate one 16-bit DMA cycle to 2 8-bit ones), but it would be a fair amount of work for not much return (who else would use it)?

You might be far better off in the long run by employing an IDE-to-CF adapter and then using either a CF card or a Microdrive in that. Both can support 8-bit DMA, unlike the overwhelming mass of IDE hard drives.
Click to expand...

I seem to recall testing this once or twice, but not extensively, and not with any results to speak of. Since the pinouts are different, I imagine you'd still need to rework the IDE-CF adapter to match the pinouts? Has anyone else tried this and gotten it to work?
Where could I find information about the XT IDE specifications?

__
Trevor
 
Broadly speaking, an XTIDE interface is roughly the same as its big brother, with the exception that the upper byte data pins are not used. (Some drives tie these pins to ground; others leave them as NC). Some drives, such as the ST351A/X, had a jumper that allowed them to operate either way. The command set is pretty much the same, with only minor differences.
 
Not been keeping up...

Not been keeping up...

For those who havent been following the blog on the 1500...

Last week I apparently managed to damage the interface for the IDE drive... once the drive begins to be accessed the indiator light (there is none on the drive itself) flashes weakly and eventually the drive access 'fails', rendering the drive nonexistent.

I have successfully accessed (and scrambled... and un-scrambled!) the CP-2024 thru the XP machine booting DOS6.22, so I feel comfortable (tho not 100% certain) that the drive itself has not been damaged.

Thru use of a copy of SpeedStor (thx again! :D ) I have seen that the BIOS on the 1500 has 4 HD configurations... the largest being comparable to the 2024 (615,4,17) and apparently it MUST boot thru one of these configurations...

But, that is in the past... for now. I also managed to trash the 810mb thru the inability to see up close when the contacts are in... but I found that it was having trouble spinning up anyway, so... small loss!

Because I dont have schematics for this machine, and doubt I will ever find any, I had put it on the back-burner... until now. Soon I will dig out the digital multimeter and see if I can find the culprit.

I would like a good reason to attempt a re-write of the BIOS... but 1st things 1st!:shock:

Thanks to all for the input and suggestions! If anyone happens to run across a schematic for a Tandy 1500HD....
 
I recently found that the HD cable (a rather delicate 'flexi-board' type) has been damaged... likely from being played with too much! :oops:

Anyway, an 1800HD has sacrificed its cable for the 1500HD, so it is working again! :D

IF/WHEN I manage to get the 1800HD's damage repaired (battery corrosion damage to motherboard), I intend to attempt modification of the 1500 BIOS to accept 'other' drives.

Stand by to be amazed! ;)
 
Lord Moz said:
... The Conner CP-2024 the only XT IDE 2.5" HD I've ever heard of, ...
... What I would love is a XT IDE -> AT IDE converter, first for my Tandy 1000 desktops, but also for my Tandy 1110HD with a dead HD.
Is a project like that within the capabilities of anyone in this forum?
Click to expand...

Chuck(G) said:
It's doable (translate one 16-bit DMA cycle to 2 8-bit ones), but it would be a fair amount of work for not much return (who else would use it)? ...
Click to expand...

On the subject... The GIDE interface I got/built for my Model 4p interfaces to IDE drives and did in fact talk to the 2024 (before I got it working)...
It does exactly what Chuck said... pulling in 2 bytes and OUTing them 1-at-a-time... and is currently attached to a 2GB 3.5in drive feeding my CP/M (a BIG waste!)

Dunno... did they change the CONTROL register(s) from 8 to 16 bits? that would be the only place I can figure that would break things...
That would be the only difference I KNOW OF that would affect the ability to read drives...
 
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