Rick Ethridge
Veteran Member
Did any IBM compatibles ever use four floppy drives? Can newer PC's use a secondary floppy controller for four floppy drives?
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Four floppy PC?
- Thread starter Rick Ethridge
- Start date
Terry Yager
Veteran Member
Yes, IBMs & many clones can use 2x internal & 2x external floppy drives (that's what the (37-pin?) external connector on IBM floppy controllers are for).
It depends on the board, some have jumpers to re-assign the address, but most do not, you're stuch with the default addresses. I've never tried to use one with a modern PC, so I don't know if there might be BIOS limitations, or what.
--T
It depends on the board, some have jumpers to re-assign the address, but most do not, you're stuch with the default addresses. I've never tried to use one with a modern PC, so I don't know if there might be BIOS limitations, or what.
--T
The original diskette controller in the IBM PC supported two driver on the internal chain and two drives on the external chain.
Most modern disk controllers only support two drives, and don't have an external port. Some can be jumpered to serve as a secondary diskette controller.
PCjrs can support up to 3 drives only.
Most modern disk controllers only support two drives, and don't have an external port. Some can be jumpered to serve as a secondary diskette controller.
PCjrs can support up to 3 drives only.
creepingnet
Veteran Member
Actually, most modern motherboards I come across only seem to support ONE floppy drive. The newest board I have ever had that supported 2 MFM Floppy type devices was a Pentium Pro board, everything else so far won't take 2 drives, except maybe if you put in an aftermarket controller.
Sanyo MBC-55x (550, 550-2, 555, 555-2, etc) had a controller for 4 floppies - when hard drives were out or if a ram disk was made it became E: as A B C and D were reserved for the floppies. The Sanyo 55x series ran an 8088 processor, XT era.
The line that JDR Microdevices sold had a few controller cards that supported 1-4 floppies but the drive letters worked differently. Pretty sure they still sell them in ISA and PCI - check their website if you were asking to be able to upgrade one of your machines to 4 floppies for whatever reason.
Did someone say the IBM came with a 4 floppy controller? If it did the card was removeable - the Sanyo's controller was imbedded just like the parallel yet the serial was an option board as was CGA, more memory and a hard drive controller. The Sanyo was supposed to be a clone yet it's native graphics emulated Apple and the bulk of the rest of the machine IBM.
The line that JDR Microdevices sold had a few controller cards that supported 1-4 floppies but the drive letters worked differently. Pretty sure they still sell them in ISA and PCI - check their website if you were asking to be able to upgrade one of your machines to 4 floppies for whatever reason.
Did someone say the IBM came with a 4 floppy controller? If it did the card was removeable - the Sanyo's controller was imbedded just like the parallel yet the serial was an option board as was CGA, more memory and a hard drive controller. The Sanyo was supposed to be a clone yet it's native graphics emulated Apple and the bulk of the rest of the machine IBM.
Mad-Mike said:
So far everything I've worked on including machines that no longer come with floppy drives (but they will sell you an outrageously priced kit to add one, ie HP/Compaq's newest) has a controller with support for D0 and D1 commonly referred to as A: and B:
Terry Yager
Veteran Member
Typical of IBM, to promise four drives, but only deliver on three.
--T
--T
mbbrutman said:
I know what you are saying - capable and engineered for 4 - but the external DEVICES that would go to the external connection had no way of daisy chaining or passing through - therefore you could only USE one on the external connection therefore it essentially was capable of only 3 in reality - unless you made your own external unit with 2 drives jumpered as DS2 and DS3 attached to the 37 pin external. If memory serves me correctly it was a non-standard pinout from the 37 as well, you had to know the pinout to build your own or modify a non-IBM external box.
SW1 also had some say in this.. 1-1 could make the controller go off or on and 7,8 settings were the number of drives 1, 2, 3 or 4. SW1 also set the memory, mathco and video basics.
BTW I have 3 of the original 5150 PC with the cassette port next to the keyboard DIN )besides 4 5160 PC/XT machines along with probably 6 5170 ATs and boxes full of old controller cards of the era). All working and pretty close to original condition...One has an NEC aftermarket CPU, the others the original Intel. All three have the IBM 6181682-987-V9116 floppy controllers, two of the three have the IBM MFM controller as well with ST412 hard drives. One runs DOS 1.25, one DOS 2.11 and one DOS 6.2
Just looked and JDR still sells the MCT ISA 4 Floppy Controller:
http://www.jdr.com/interact/item.asp?itemno=MCT-FDC-HD4
paul
Veteran Member
Once you get into the AT-class machines I don't think the secondary floppy controller was supported in the BIOS. Certainly many floppy controllers could be addressed as such however, but I think you would need a DOS device driver.
All this applies to the secondary hard disk controller as well, before they became integrated into the motherboards.
Funny that there are four DS (drive select) lines on each controller cable and disk drive, yet only two or three are used. The Compaq DeskPro 386 that I used to have had support for (3) floppy drives right off the same cable. I think there was a device driver for the third, so it had a configurable drive letter.
And (off topic,) that Compaq also had the first IDE interface that I was aware of, even though it was not called that at the time.
All this applies to the secondary hard disk controller as well, before they became integrated into the motherboards.
Funny that there are four DS (drive select) lines on each controller cable and disk drive, yet only two or three are used. The Compaq DeskPro 386 that I used to have had support for (3) floppy drives right off the same cable. I think there was a device driver for the third, so it had a configurable drive letter.
And (off topic,) that Compaq also had the first IDE interface that I was aware of, even though it was not called that at the time.
Rhblake:
IBM didn't sell an external drive with passthrough capability. But the external cable to support two drives was sold by places like JDR, etc. The cable on the external connector supports two drives just like the cable on the internal connector does - you need to do the 'twist' in the cable to address the two drives differently, or you need to jumper the drives differently.
What non-standard pinout are you referring to? The 37 pin external interface had 3 extra wires for voltage and grounding. But it was always the same 37 pin assignments.
Terry:
On the PCjr IBM promised one drive but mostly delivered on three. ;-)
IBM didn't sell an external drive with passthrough capability. But the external cable to support two drives was sold by places like JDR, etc. The cable on the external connector supports two drives just like the cable on the internal connector does - you need to do the 'twist' in the cable to address the two drives differently, or you need to jumper the drives differently.
What non-standard pinout are you referring to? The 37 pin external interface had 3 extra wires for voltage and grounding. But it was always the same 37 pin assignments.
Terry:
On the PCjr IBM promised one drive but mostly delivered on three. ;-)
creepingnet
Veteran Member
paul said:
The 3rd connection on the Compaq Deskpro 386's floppy connector was probably for the tape backup unit that hardly anyone bought. I've noticed that most of the tape backup units of that era (1986-onward) seem to all be mfm devices that usually plug into the floppy drive cable.
As for IDE, I think the later Deskpro 386/16 (REV 2 motherboard) and Deskpro 286/12 came with it standard, usually with a quasi-proprietary 30,40, 60, 80, or 160 MB hard disk drive. On my old Deskpro 386/16 I sold before moving to another state, it had a panel inside that marked the IDE controller card as an "ESDI/ST-506 controller card" in the diagram, so it may have very well been the first. But I don't know for sure.
Mad-Mike said:
The ST-506 is a form of MFM controller known as ESDI that came after RLL which was another MFM type with different encoding. It was out before IDE and most units that it actually was found on were the IBM PS/2 lines mostly in the 85xx series - most of the 95xx series transitioned to IDE for the most part or stayed with SCSI. I have a model 8565 and 8580 both with FH 5.25" heavy ESDI drives and numerous models with 3.5" with a proprietary card edge connector that are all ESDI. The biggest capacity of ESDI that I have worked with is 160mb.
Here's a little blurb on it:
http://www.hardwarecentral.com/hardwarecentral/tutorials/40/1/
Terry Yager
Veteran Member
Mad-Mike said:
I remember having a few Colorado tape drives that ran off the floppy drive connector. They usually came with an appropriate cable that tied-in to the floppy controller, and the system would see them as a third drive.
--T
Terry Yager said:
Most were DC2120 types, QIC-80 format, 120mb capacity. The Colorado(now part of HP as Conner is now part of Seagate) drives came with an adapter to chain off the floppy cable and on some models a total replacement that had 3 connectors on it. I still run one on my 5170 AT. It does not use a DS allocation, the software talks directly to it, DOS and windows do not give it a drive letter.
My servers are backed up with tape but much larger capacity but smaller cartridge sized DAT tapes, on the SCSI controller - the MFM channel for the floppies is just too slow for the 1.2 terrabytes of space I have. I could use DVD-R or +R but that would involve manual interaction rather than a library of tapes that auto-switch. My tape library was about $2500 new, I bought it at a surplus sale for $50.
Terry Yager
Veteran Member
Yes. I've used DAT tape drives too, with a capacity of about 2Mb per drive.
--T
--T
Terry Yager said:
Not sure that you mean DAT here as DDS1 DAT is 2 GIGAbyte, 4 compressed. Even the old DC2000 (not DAT, QIC 40 or 80?? MFM on floppy controller) tapes were 40 mb. A 3.5" DSHD floppy is 2mb although DOS and Windows only format to 1.44mb. I believe Apple may go higher as their 3.5 DSDD that we get 720k out of is 800k on many older Apples.
I run an HP DDS4 x 6 autoloader which is 20 GIGAbyte/40 compressed -per tape- with a library of 6 autoloaded tapes. I have a full set of the initial setup then use differential to catch only new and updated files. Certain files are also duplicated on another machine that has a removable 250gb HD, one of two that can slide into the bay. One of the redundant copies goes to a firesafe then other stays until it's update time.
Terry Yager
Veteran Member
I quit using the (scsi) DAT setup when one of my two drives went non-functional. By that time, it was more econimically sensible to use the CD burner for system backups.
--T
--T