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evildragon
October 16th, 2013, 03:28 PM
I want to adapt a 5.25 drive to my model 25, but I can't use one of those regular IBM ones as it uses an ISA slot to run.

I was wondering, since the BIOS in my model 25 works fine with 1.44MB drives too, maybe I can somehow adapt a 1.2MB 5.25" as the B: drive, and adapt it to the internal ribbon, run it external to an enclosure? I hope this can be done somehow.

Otherwise I may have to sacrifice my sound blaster.

PeterNC
October 23rd, 2013, 06:57 PM
There are IBM 5.25" external FDDs with an ISA card to connect out there. Is that an option?

evildragon
October 23rd, 2013, 07:59 PM
There are IBM 5.25" external FDDs with an ISA card to connect out there. Is that an option?

As per "but I can't use one of those regular IBM ones as it uses an ISA slot to run.", no.

But, if I absolutely must, then I might do just that. I was hoping the signals on the normal cable can be adapted to the 5.25" drive, and maybe the model 25 wouldn't have issue.

krebizfan
October 23rd, 2013, 08:37 PM
You don't have to sacrifice the soundblaster. Just track down one of the parallel port drives and modify it to use 5.25" high density.

I remember seeing an adaption of an internal floppy connector to run to a floppy located outside the system. Here is a link to doing that for an 8" drive. http://www.classiccmp.org/dunfield/img54306/cnct.htm I suspect with some effort the concept could be modified to work with a more typical PC drive if you absolutely need to have the 5.25" on a Model 25 without using either slot (for a proper controller with external connector) or parallel port.

Chuck(G)
October 23rd, 2013, 09:43 PM
Looking at the Model 25 Technical Reference Manual (http://bitsavers.trailing-edge.com/pdf/ibm/pc/ps2/PS2_Model_25_Technical_Reference_Jun87.pdf), I note that the 25 has the Type 1 controller and so does not support 300Kbps mode. What that means is that the controller will support a 1.2MB drive in 360K mode only in dual-speed (360/300 RPM) mode. Some 1.2M drives can be jumpered for this. Type 2 controllers do have the 300Kbps modes.

There's no reason that you can't fabricate a drive extension cable--the controller does support 2 drives.

evildragon
October 23rd, 2013, 10:23 PM
Looking at the Model 25 Technical Reference Manual (http://bitsavers.trailing-edge.com/pdf/ibm/pc/ps2/PS2_Model_25_Technical_Reference_Jun87.pdf), I note that the 25 has the Type 1 controller and so does not support 300Kbps mode. What that means is that the controller will support a 1.2MB drive in 360K mode only in dual-speed (360/300 RPM) mode. Some 1.2M drives can be jumpered for this. Type 2 controllers do have the 300Kbps modes.

There's no reason that you can't fabricate a drive extension cable--the controller does support 2 drives.
I have to admit, the model 25 tech ref manual isn't all correct.

I am using a 1.44MB drive currently and it read and writes to these disks without any issue.. Wouldn't that also require a 300Kbps mode?

Chuck(G)
October 23rd, 2013, 10:42 PM
I have to admit, the model 25 tech ref manual isn't all correct.

I am using a 1.44MB drive currently and it read and writes to these disks without any issue.. Wouldn't that also require a 300Kbps mode?

No, the "360K" mode of a 1.2M drive is a bit of an odd egg. Normally, a PC-AT style 1.2M drive spins at a constant 360 RPM, while a 1.44M drive spins at a constant 300 RPM. That's why, for example both drives have 80 cylinders, you only get 1.2M instead of 1.44M (1.44 * (300/360)).

So, to get 360K on a 360 RPM 5.25" drive, the data rate would have to be ((360/300)*250Kbps) =
300Kbit/sec.

Now, some 5.25" 1.2M drives (e.g. Teac FD55HG) can be jumpered to "downshift" to 300 RPM in 360K mode, based on the setting of the "density select" signal line.

A 720K drive (as well as a 360K) uses a data rate exactly half of the 500Kbit/sec high-density rate. So, you could use a 360K drive rather than a 1.2M and you'd be fine.

evildragon
October 23rd, 2013, 11:31 PM
No, the "360K" mode of a 1.2M drive is a bit of an odd egg. Normally, a PC-AT style 1.2M drive spins at a constant 360 RPM, while a 1.44M drive spins at a constant 300 RPM. That's why, for example both drives have 80 cylinders, you only get 1.2M instead of 1.44M (1.44 * (300/360)).

So, to get 360K on a 360 RPM 5.25" drive, the data rate would have to be ((360/300)*250Kbps) =
300Kbit/sec.

Now, some 5.25" 1.2M drives (e.g. Teac FD55HG) can be jumpered to "downshift" to 300 RPM in 360K mode, based on the setting of the "density select" signal line.

A 720K drive (as well as a 360K) uses a data rate exactly half of the 500Kbit/sec high-density rate. So, you could use a 360K drive rather than a 1.2M and you'd be fine.

I'll need to see what I can interface on this..

Since the model 25 has no BIOS setup, how would I tell it what kind of drive is attached? The 1.44MB drive when plugged in "just works" (in the words of the late mr. jobs).

Chuck(G)
October 24th, 2013, 09:15 AM
I'll need to see what I can interface on this..

Since the model 25 has no BIOS setup, how would I tell it what kind of drive is attached? The 1.44MB drive when plugged in "just works" (in the words of the late mr. jobs).

After looking more at the tech ref, it seems that the model 25 uses a simple NEC 765 controller with none of the extra foof of its big brother (e.g. model 70) controllers. So, basically, it seeks to some track, then back to track 0 to see if the track 0 sensor lights up. If it does, there's a drive there.

Now, here's the rub. 1.2M 5.25" drives, in order to operate in both high- and low-density modes use pin 2 as a signal to tell them what's supposed to be done. 3.5" drives generally don't use this method, relying upon the density aperture in the diskette to tell them what's in the drive. So, on the model 25, you have the issue of not being able to select the drive write data rate for 5.25" disks. Thus, you'll be stuck in one mode or the other. Absent supplying switch on that pin to manually toggle the mode, you're out of luck.

Another question that arises is if the model 25 BIOS contains code to double-step the drive in 360K mode. I'm going to guess that it doesn't.

So, for the best performance, you'll need a separate controller to run that drive. You can take a Microsolutions Backpack unit and re-house it with a 5.25" drive and use it as a parallel port drive, however.

evildragon
October 24th, 2013, 10:49 AM
After looking more at the tech ref, it seems that the model 25 uses a simple NEC 765 controller with none of the extra foof of its big brother (e.g. model 70) controllers. So, basically, it seeks to some track, then back to track 0 to see if the track 0 sensor lights up. If it does, there's a drive there.

Now, here's the rub. 1.2M 5.25" drives, in order to operate in both high- and low-density modes use pin 2 as a signal to tell them what's supposed to be done. 3.5" drives generally don't use this method, relying upon the density aperture in the diskette to tell them what's in the drive. So, on the model 25, you have the issue of not being able to select the drive write data rate for 5.25" disks. Thus, you'll be stuck in one mode or the other. Absent supplying switch on that pin to manually toggle the mode, you're out of luck.

Another question that arises is if the model 25 BIOS contains code to double-step the drive in 360K mode. I'm going to guess that it doesn't.

So, for the best performance, you'll need a separate controller to run that drive. You can take a Microsolutions Backpack unit and re-house it with a 5.25" drive and use it as a parallel port drive, however.
Hmm, to gain a parallel port the sound blaster would still have to go.. Primary parallel port has a xircom PE3 on it right now. I may just do this though in the end.. I do need my 5.25" disks.

Chuck(G)
October 24th, 2013, 12:11 PM
You don't need a second parallel port--you can daisy chain the Backpack--I've certainly done that.

evildragon
October 24th, 2013, 12:14 PM
You don't need a second parallel port--you can daisy chain the Backpack--I've certainly done that.

When I did that with my PE3 on my Backpack Bantam, the PE3 would quit working after CD-ROM access.. Apparently do to some IRQ problem.

Chuck(G)
October 24th, 2013, 02:37 PM
I think less IRQ than perhaps confusion over the protocol.

With legacy parallel-port devices, each manufacturer had its own protocol, the thought being that as long as you don't use the data strobe (pin 1 on the DB23 interface) to do data transfer, you'd be safe from activating any printer. Obviously, there's some conflict the the two (XE3 and Backpack) protocols.

Perhaps an A-B printer switch might be acceptable.

evildragon
October 24th, 2013, 04:50 PM
I think less IRQ than perhaps confusion over the protocol.

With legacy parallel-port devices, each manufacturer had its own protocol, the thought being that as long as you don't use the data strobe (pin 1 on the DB23 interface) to do data transfer, you'd be safe from activating any printer. Obviously, there's some conflict the the two (XE3 and Backpack) protocols.

Perhaps an A-B printer switch might be acceptable.

I do actually have an A-B switch, but I'm not sure if manually selecting a device to use, would be wise. Like what happens if i accidentally try to access the CD-ROM drive and have PE-3 selected? I would think that may crash the driver and thus the computer.. :/

I gotta say, the model 25 is limited like crazy.

Chuck(G)
October 24th, 2013, 04:57 PM
I do actually have an A-B switch, but I'm not sure if manually selecting a device to use, would be wise. Like what happens if i accidentally try to access the CD-ROM drive and have PE-3 selected? I would think that may crash the driver and thus the computer.. :/

I gotta say, the model 25 is limited like crazy.

Well, it wouldn't hurt to try it.

But wasn't the point of the model 25 to compete on a low-cost basis with the Mac in educational environments? Really. it's not much more than an XT in a different box. That sad thing is that a PC XT is more expandable.

evildragon
October 24th, 2013, 06:52 PM
Well, it wouldn't hurt to try it.

But wasn't the point of the model 25 to compete on a low-cost basis with the Mac in educational environments? Really. it's not much more than an XT in a different box. That sad thing is that a PC XT is more expandable.

Well yea, it was meant to be in educational markets, and in my schools, they made it.. My dad bought this sucker brand new though for the home.. So, it's more sentimental than practical. I stick with it's limits because I want this machine, nothing else.

PeterNC
October 25th, 2013, 09:47 AM
How about getting to 5.25" through FastLynx / LapLink from another box?

Chuck(G)
October 25th, 2013, 10:27 AM
How about getting to 5.25" through FastLynx / LapLink from another box?

Why bother? ED already has an ethernet adapter installed. If he needed to transfer files, he'd already have a way via standard networking. I suspect that he doesn't have another box.

If he does have another box with 3.5 and 5.25" drives on it, he could simply copy the 5.25" information to a 3.5" disk and be done with it.

evildragon
October 25th, 2013, 12:15 PM
Why bother? ED already has an ethernet adapter installed. If he needed to transfer files, he'd already have a way via standard networking. I suspect that he doesn't have another box.

If he does have another box with 3.5 and 5.25" drives on it, he could simply copy the 5.25" information to a 3.5" disk and be done with it.

Yep, I could.

There is also the issue where some 5.25" games have copy protection on them..

Stone
October 25th, 2013, 12:27 PM
Just another good example of why I don't like or have any PS/2 machines. :-)

I have always stayed with IBMs, clones and compatibles for this and lots of other reasons. And PS/2s are rarely compatible with anything. :-)

krebizfan
October 25th, 2013, 12:54 PM
Just another good example of why I don't like or have any PS/2 machines. :-)

I have always stayed with IBMs, clones and compatibles for this and lots of other reasons. And PS/2s are rarely compatible with anything. :-)

Model 25 is just an all-in-one XT and has the same problems of being a small case with few expansion slots that hit portables, laptops, Tandy 1000s and the like. Nothing about it is a PS/2 specific compatability issue.

Stone
October 25th, 2013, 01:42 PM
Model 25 is just an all-in-one XT and has the same problems of being a small case with few expansion slots that hit portables, laptops, Tandy 1000s and the like. Nothing about it is a PS/2 specific compatability issue.Not having five or more slots *is* exactly part of the compatibility issue. :-) BTW, i said compatibility, not compatability -- I don't even know what compatability means, if anything. :-)

Chuck(G)
October 25th, 2013, 02:30 PM
Yep, I could.

There is also the issue where some 5.25" games have copy protection on them..

Well, if you have the capability (e.g. Option Board) to copy protected floppies, you can still copy them onto 3.5" with no issues. A 360K can be copied onto a 720K 3.5" floppy and a 1.2M can be copied onto a 1.44M one--the latter will involve adding some filler to the end of the track, but that shouldn't matter to any software. My copy of 286 Xenix was originally on 5.25" HD media and I transferred it over to 3.5" with no problem at all.

Caluser2000
October 25th, 2013, 02:36 PM
Just another good example of why I don't like or have any PS/2 machines. :-)

I have always stayed with IBMs, clones and compatibles for this and lots of other reasons. And PS/2s are rarely compatible with anything. :-)Dosn't make sense IBM made PS/2s. What exactly are you trying to say?

Stone
October 25th, 2013, 03:04 PM
Dosn't make sense IBM made PS/2s. What exactly are you trying to say?Simple, PS/2 is not 'IBM compatible' -- no matter who made it! :-) 'IBM compatible' uses ISA architecture -- PS/2 does not.

vwestlife
October 25th, 2013, 03:10 PM
'IBM compatible' uses ISA architecture -- PS/2 does not.

Many PS/2s used the ISA bus: all PS/2s with model numbers below 50, as well as the PS/2 "E" (http://www.youtube.com/watch?v=N63_aZgPeaE).

Stone
October 25th, 2013, 03:24 PM
Many PS/2s used the ISA bus: all PS/2s with model numbers below 50, as well as the PS/2 "E" (http://www.youtube.com/watch?v=N63_aZgPeaE).Ya', and those had other incompatibility issues e.g., the drives, connectors and such. All in all a series of computers (PS/2) I have always avoided and have no regrets. And no headaches, either. :-)

Caluser2000
October 25th, 2013, 03:24 PM
Simple, PS/2 is not 'IBM compatible' -- no matter who made it! :-) 'IBM compatible' uses ISA architecture -- PS/2 does not.You keep saying that but it's not accurate. Rant on regardless though. I'm sure it gives everyone a chuckle.

And please can we get back on topic?

evildragon
October 25th, 2013, 05:13 PM
Simple, PS/2 is not 'IBM compatible' -- no matter who made it! :-) 'IBM compatible' uses ISA architecture -- PS/2 does not.

And the model 25 IS an ISA architecture. It's basically a mini XT. Even complete with cassette BASIC too.

evildragon
October 25th, 2013, 05:15 PM
Well, if you have the capability (e.g. Option Board) to copy protected floppies, you can still copy them onto 3.5" with no issues. A 360K can be copied onto a 720K 3.5" floppy and a 1.2M can be copied onto a 1.44M one--the latter will involve adding some filler to the end of the track, but that shouldn't matter to any software. My copy of 286 Xenix was originally on 5.25" HD media and I transferred it over to 3.5" with no problem at all.

Sweet, I may be able to do this then.. That will be more feasible.

vwestlife
October 26th, 2013, 05:12 PM
And the model 25 IS an ISA architecture. It's basically a mini XT. Even complete with cassette BASIC too.

I was once working on a mid-'90s IBM Aptiva and was surprised to see it drop into Cassette BASIC after I formatted the hard drive and didn't put in a boot disk. All PS/2s and PS/1s have it as well, and in the original release of IBM DOS 5.0, QBASIC will crash if you run it on a computer that doesn't have ROM BASIC (http://www.os2museum.com/wp/?p=726). (In IBM DOS 5.0.1, they modified QBASIC to remove the ROM BASIC check, so it can run on non-IBM systems.)

evildragon
October 26th, 2013, 05:16 PM
I was once working on a mid-'90s IBM Aptiva and was surprised to see it drop into Cassette BASIC after I formatted the hard drive and didn't put in a boot disk. All PS/2s and PS/1s have it as well, and in the original release of IBM DOS 5.0, QBASIC will crash if you run it on a computer that doesn't have ROM BASIC (http://www.os2museum.com/wp/?p=726). (In IBM DOS 5.0.1, they modified QBASIC to remove the ROM BASIC check, so it can run on non-IBM systems.)

Nice, I didn't know that. I knew about QBASIC, but not about the PS/2's and PS/1's having it, kinda surprised.

IBMMuseum
October 28th, 2013, 04:49 PM
I want to adapt a 5.25 drive to my model 25, but I can't use one of those regular IBM ones as it uses an ISA slot to run.

I was wondering, since the BIOS in my model 25 works fine with 1.44MB drives too, maybe I can somehow adapt a 1.2MB 5.25" as the B: drive, and adapt it to the internal ribbon, run it external to an enclosure? I hope this can be done somehow.

Otherwise I may have to sacrifice my sound blaster.

I'm not sure if you mean the external 4869 external drives when you say "those regular IBM ones". There was aftermarket (Procomm and Sysgen were the more commonly-known brands, although there were others) solutions that didn't need a card in the expansion bus, but they did use a bracket cover for the internal ribbon cable to connect to an exterior DB-37 cable. A few years back I believe I had a 1.2Mb drive operational from the 8086-level Model 25 and Model 30.

Trixter
October 29th, 2013, 10:59 AM
Sweet, I may be able to do this then.. That will be more feasible.

As a data point, I used to do this for friends back in the day. Protected 5.25" 360K disk to protected 720K 3.5" disk with an option board and I don't recall there ever being a problem. The 3.5" disk shows only 360K of data, obviously.