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Continuing saga of my 5150...

Al Hartman

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I had a clone PC/XT case with 4 floppy drives in it, that we used to use at Zebra Systems, Inc. as our Coco disk duplication station.

I decided to turn it into a working PC, so I could run emulators and make 5.25" floppies using Imagedisk.

I bought a 5150 logic board on eBay, and mounted it up.

Earlier episodes covered converting the motherboard from a 256k board to 640k board, getting the software for an Everex Multi I/O to enable the clock/calendar, attaching an external 3.5" drive when I had no cable, no power supply, and no drivers.

Next, I built a Lo-Tech 8-Bit IDE adapter board that works great with an old Miniscribe hard drive.

The most recent hurdle was putting an Oak 8-Bit EGA/VGA card in it so I could use a more modern display rather than using the composite output of a CGA card to drive a monochrome composite monitor, or a TV.

The next thing I wanted to do with this system was to replace the floppy disk controller. The one it had was a long card controller, but someone had mangled the metal bracket on it, so it couldn't be fastened down to the case. Also, the controller failed all the TESTFDC tests, and wouldn't write a single density floppy disk.

I bought a Magitronic half-card floppy controller on eBay for $24.00, but when I got it... it didn't work. I'd get a 601 error on boot. Examining the card, it looked fine. No burnt caps or damaged chips. No chips seemed hot to the touch either.

Just for kicks, I cleaned the connector contacts which seemed tarnished to me. Got them nice and bright, and shiny.

I reinserted the card, restarted the system, and it now works great!

But, the system still fails all the TESTFDC tests.

*sigh*

I wonder if the XT-FDC board works with Single Density? Before I undertake building one, I'd like to know if it will work. Otherwise, I'll go locate a 3.5 to 5.25 bracket adapter, fasten down the hard drive and button up the case, so I can try out some of my older systems to see if one of those would write single density disks.
 

modem7

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I wonder if the XT-FDC board works with Single Density? Before I undertake building one, I'd like to know if it will work.
Perhaps the designers of the XT-FDC, members Chuck(G) and lynchaj, will comment, in addition to my comments below.

The 'standard' FDC chip used in the XT-FDC is the PC8477B, which sits in socket U16.
The XT-FDC can optionally use a DP8473V or 82077AA in socket U2, instead of the PC8477B (removed from socket U16).

Chip PC8477B

A reference to single density (FM) in the PC8477B datasheet is, "The PC8477B supports the standard PC data rates of 250, 300, 500 kb/s, and 1 Mb/s in MFM encoded data mode, but is no longer guaranteed through functional testing to support the older FM encoded data mode."

So it sounds like a hit-or-miss affair. This was discussed/answered in posts #21 to #24 in the thread at [here].

Chip DP8473V

The DP8473V datasheet contains, "While the controller and data separator support both FM and MFM encoding, the filter switch circuitry only supports the IBM standard MFM data rates. To provide both FM and MFM filters external logic may be necessary."

The 'external logic' was not added to the XT-FDC, but that does not mean that FM won't work. It possibly just means that the XT-FDC (using DP8473V) is not optimised for FM operation.

Chip 82077AA

According to the post [here], quote, "I'd stay away from Intel, as they broke FM support a long time ago in the 82077AA-1 and succeeding chips".
This suggests that the original 82077AA would be required for FM.
Note the problem stated [here] about an 82077AA in an XT-FDC (some people could not get the combination to work).
 

bonedaddy

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May 2, 2012
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Location
Candia, NH USA
I wonder if the XT-FDC board works with Single Density? Before I undertake building one, I'd like to know if it will work. Otherwise, I'll go locate a 3.5 to 5.25 bracket adapter, fasten down the hard drive and button up the case, so I can try out some of my older systems to see if one of those would write single density disks.

Sergey's ISA FDC/Serial board at http://www.malinov.com/Home/sergeys-projects/isa-fdc-and-uart supports single density. You can use either an Intel 82077AA or National Semiconductor PC8477.

I have the bare PCBs available. PM me here or email me at tsg at bonedaddy.net if you're interested.

You'd have to source the parts and build it yourself but that's a lot of fun!

Todd
 

Al Hartman

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Sergey's ISA FDC/Serial board at http://www.malinov.com/Home/sergeys-projects/isa-fdc-and-uart supports single density. You can use either an Intel 82077AA or National Semiconductor PC8477.

I have the bare PCBs available. PM me here or email me at tsg at bonedaddy.net if you're interested.

You'd have to source the parts and build it yourself but that's a lot of fun!

Todd

How much is a blank board?

I've built several of jj_pearce's boards, and that was fun. So, building an FDC controller sounds like it might be fun.
 

Malc

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$10 according to here, I got 1 and still haven't built it a year later, Nice board though, I actually found a couple of old cards that passed the "TestFDC" test and used those
 

Malc

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As far as i know you can use XTIDECFG.COM thats included with the XT-IDE Bios, to program the BIOS to the XT-FDC chip.
 

Al Hartman

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Sergey's ISA FDC/Serial board at http://www.malinov.com/Home/sergeys-projects/isa-fdc-and-uart supports single density. You can use either an Intel 82077AA or National Semiconductor PC8477.

I have the bare PCBs available. PM me here or email me at tsg at bonedaddy.net if you're interested.

You'd have to source the parts and build it yourself but that's a lot of fun!

Todd

Sent you a PM.

I have two questions (for anyone)

1. Where should I put the extension ROM to make it compatible with the Lo-Tech CF Adapter Board? ( http://www.lo-tech.co.uk/wiki/Lo-tech_ISA_CompactFlash_Adapter_revision_2 ). I put an SST27SF010 1Mbit flash chip on the XT-IDE.

I know I could put the XT-FDC BIOS on the XT-IDE card, but I don't want them locked together as a pair.

2. Nobody has given me a foolproof method to program the XT-FDC Extension ROM BIOS similar to the instructions on the Lo-Tech page.

I ordered the parts from Mouser (they didn't have some of the serial port parts, so I'm leaving that off for now.), and an FDC from eBay (a National Semiconductor PC8477BV-1).

All the Lo-Tech adapters I've built so far worked first time, without problems. So, I'm hoping this will work well.
 

modem7

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As far as i know you can use XTIDECFG.COM thats included with the XT-IDE Bios, to program the BIOS to the XT-FDC chip.
2. Nobody has given me a foolproof method to program the XT-FDC Extension ROM BIOS similar to the instructions on the Lo-Tech page.
I confirm that you can use XTIDECFG.COM
I have just now used version 1.1.5 of it (together with an image file of the BIOS) to flash a blank AT28C64B fitted in my XT-FDC.
XTIDECFG.COM is menu driven, simple, and self-expanatory (but not foolproof).

Note: The AT28C64B differs to the AT28C64 in that the B version has SDP (software data protection) functionality. If you use an AT28C64 instead of an AT28C64B, you may need to disable the 'SDP command' option in XTIDECFG.COM (it is one of the options in the flash menu).
 

Al Hartman

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Note: The AT28C64B differs to the AT28C64 in that the B version has SDP (software data protection) functionality. If you use an AT28C64 instead of an AT28C64B, you may need to disable the 'SDP command' option in XTIDECFG.COM (it is one of the options in the flash menu).

I ordered the "B" version, as that is what Sergey calls for.
 

Al Hartman

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I started my boards tonight. One is mostly done. I just need to solder a cap, then the chip sockets I have in my parts box, and then wait for the rest of the parts.

I should have both boards up and running by the end of next week, assuming I don't run into any problems like a bad part.
 

Al Hartman

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I didn't post here that I ended up buying the parts to do the serial ports. Fully built up both boards, programmed them both with XTIDECFG, tested them with a 360k and 1.44mb drive and they worked great.

Used Checkit and a serial loopback plug and both serial ports test perfectly!

Writes single density/mixed density TRS-80 disks perfectly!

Can't recommend this card more highly!

I think I'm going to try an OPL sound board in a few months.
 
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