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floppy drive woes. (IBM model 25)

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luckybob

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It seems like this machine is going to fight me on everything I try to do with it. For the record, my penultimate goal would be to have a 1.4mb 3.5 floppy internal, original hard drive, and an external IBM branded 1.2mb 5.25 drive. I have a small pile of 5.25 booter games i'd like to be able to use.

A month ago, I found a business-land internal to external floppy drive adapter. It seems it was specifically designed for IBM PS/2's and is about as 'plug-and-play' as one could expect. However, no matter what I tried, it would not work. The bios will "see" the drive and label it at B: automatically, but it could not read or write any disks. I am inclined to believe that the bios is expecting a 720k 3.5 drive and refuses to acknowledge anything else.

So I gave up on that when I found a box of ide cards on ebay. The jewel in the box was a Future Domain TMC-885. http://stason.org/TULARC/pc/hard-di...p-to-seven-SCSI-devices-198.html#.Ubo_avm1G30

This card is supposed to be bootable isn't it? The bios will respond during post, but if I disconnect the on-board hard drive, it still won't boot. I can't seem to disable the onboard ide/floppy interface. The starter disk is NO help at all. It is nothing more than a glorified diagnostic disk. That said, if I boot to dos from another source, I can use the utilities I found on Adaptec's website to access the hard drive. I can low level the drive as well as basic diagnostics and everything comes back fine, however the drive isn't being reported to dos by the bios. So fdisk fails.

What am I missing here? I have to admit my knowledge of pre-286 machines would fill a business card on a good day. Any assistance would be appreciated.
 
I'm fairly certain that IBM required the use of an IBM branded SCSI adapter in the Model 25, such as the TMC-850IBM
 
the 850 is just a scsi card without the floppy bits. same processors as the 855, I wonder if it is just a firmware issue. maybe upgrading from 6.02 to 8 (or whatever) would help?
 
luckybob said:
the 850 is just a scsi card without the floppy bits. same processors as the 855, I wonder if it is just a firmware issue. maybe upgrading from 6.02 to 8 (or whatever) would help?
Click to expand...

My 850 has an IBM copyrighted BIOS, works great in my Model 25 (pretty sure it was made for Model 25/30 use). I could try to dump it if someone wanted to burn it to a NON-IBM 850 card (or if you wanted to try it on your 855, probably loosing its FDC abilities).

I know the 25 is a fickle ***** when it comes to bootable add-in cards as to where their memory address is, you could try playing with that, also without being able to disable the onboard FDC, I seriously doubt you will ever get a the floppy working on your add-in card, unless it can be set as some kind of secondary FDC (which might look possible based on jumpers, not sure though).

There IS some hope to getting a 1.44 internal on the onboard FDC though, I will wait till evildragon stops by to tell us which exact models work, but the 25 CAN see certain models of the "small button" 1.44MB PS/2 floppy drives.
 
I certainly would not mind a copy of your bios! I ordered a programmer just the other day and as soon as it gets here from the great white north. I have actually 4-5 projects I need to finish with it! While on the subject, I couldn't find any mention of an updated bios/firmware for the model 25. My chips are marked 1.2 is there something newer out there? maybe something that plays nice with upgrades?
 
luckybob said:
I certainly would not mind a copy of your bios!
Click to expand...
I will try to work on that this coming weekend, only have so much room to work on my old PCs right now, and right now the 25 isn't on the bench.

luckybob said:
I ordered a programmer just the other day and as soon as it gets here from the great white north.
Click to expand...
Out of curiosity, I have been thinking about buying a programmer, what one did you go with?

luckybob said:
I couldn't find any mention of an updated bios/firmware for the model 25. My chips are marked 1.2 is there something newer out there? maybe something that plays nice with upgrades?
Click to expand...
As far as the Model 25 BIOS I do not know of any other revisions, but I could be wrong.
 
luckybob said:
When I asked for advice here, this one came highly recommended: http://www.mcumall.com/comersus/store/comersus_viewitem.asp?idproduct=4282

I probably could have gotten a knockoff from china but in all honesty, the less I buy from that place the better.
Click to expand...

I will have to check them out, and I hear ya, can get a lot of stuff cheaper from china, but in general you get what you pay for, sometimes its best to pony up the cash for quality, especially for tools that you will use a lot ;-)

luckybob said:
Also, I actually meant a copy of the scsi bios, not the model 25's. (unless yours is different, then both would be awesome!)
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Yeah, I knew that, still have to get it out of storage and on to my bench to dump the ROM ;-)
 
luckybob said:
When I asked for advice here, this one came highly recommended: http://www.mcumall.com/comersus/store/comersus_viewitem.asp?idproduct=4282

I probably could have gotten a knockoff from china but in all honesty, the less I buy from that place the better.
Click to expand...
Dont worry - that programmer is still made in China, and has complete with Chinglish instruction manual :) That said... it works well. Has a bit of trouble with the higher-voltage chips, but you can use an external power adapter to give it the extra oomph necessary. All in all, it's a solid buy, and one that several of forums members use.
 
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