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XT-FDC project level of interest

Please forgive me if this has already been discussed, as I arrived late and I have not read the whole thread. Has anybody tested out the XT-FDC with the TestFDC utility from ImageDisk yet? If so, I'm interested in finding out which tests it passed and failed.
 
NF6X said:
Has anybody tested out the XT-FDC with the TestFDC utility ... yet? If so, I'm interested in finding out which tests it passed and failed.
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modem7 said:
I will try it this weekend.
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Chuck(G) said:
If you're using the PC8477 or the NS8473, it will pass. If you're using the Intel 82077AA-1, it will fail on FM write.
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An answer from someone well experienced in the area. I won't bother then.
 
There's ample data as well as real-world experience. I was the one to recommend both chips, having had at least 2 decades of experience with them. When Intel brought out the 82077AA-1 revision of the 82077, I contacted Intel and told them that they'd broken the FM write function. I was blown off with "who uses FM today anyway?" and Intel did nothing.

Back around 1990, Microsolutions had been equipping their Compaticard IV with the 82077 and had to replace chips in customer units when they switched to the new Intel part. Fortunately for them, the National PC8477 is nearly identical in pinout, so a swap saved the product.

The National DP8473 was noted back in the day by both Don Maslin and myself as having not only FM support done right, but also being able to read and write 128-byte MFM sectors--something that not even the original NEC 765 can do. Kudos to National for doing things right.

I'll buy dinner for anyone to prove me wrong.

I have one of the early prototypes of the XT-FDC as well as a later version. I can state categorically that my observations are backed up by personal testing. For what it's worth, I didn't bother to populate my cards past the FDC portion.
 
Either NS chip will work just fine, but the 8473, as I mentioned, will give you 128-byte sector MFM mode. That was used by a few CP/M systems, such as some Jade and Superbrain models. There may have been a Cromemco 8" format that used that, but my memory fails me.

The 8473 is the same chip used on some 16 bit SCSI controllers, such as DTC and Adaptec and a couple of Future Domain, which is why they're often recommended as in-a-pinch controller for 8-bit systems (the SCSI part is, of course, useless for 8 bits). It was also used on the DTK Mini-micro floppy controller.

On the other hand, the 8477 is a bit easier to find and does include support for 2.88MB (ED) drives as well as some of the faster floppytapes.
 
Well, I bought the chip recommended on the XT-FDC page. A National Semiconductor PC8477BV-1 .

Parts (less serial port) were around $30.00, the PCB will be $10.00 + shipping, I think. So, for a little over $40.00 (taking some parts from my parts box), I'll have a board I see selling for $100 or more on eBay.
 
Actually, you get about the same functionality as a Compaticard IV. I've seen them selling in excess of $200 on eBay.

If anyone wants to try it, the FDCs using the Hynix/Goldstar GM82c765 might be worth a look. The chip seems to be a clone of the Western Digital WD37C65, which does handle FM fairly well.

I haven't tried any Goldstar chips, myself.
 
I had ordered 2 boards. I decided to populate the serial port function as I found the right angle serial connector on eBay.

I had to buy 10. So, I'll have 8 left over. If anyone needs one in the U.S. I can probably provide them for $2.50 each including shipping (which is most of the cost.)

Sergey makes it easy to order parts. He gives you links to Mouser for most all of the parts. The only things I had to order separately were the FDC chip, the Serial Port connector, and the 34-pin box header for the floppy connector. I got all of those on eBay.

I'd love to build more of his boards. I'm looking at the OPL-3 board as my next project.
 
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The OPL-3 Board is a nice project :) Just be careful of your cap values - there are some similar values, and I ended up getting my "readings" reversed when building. Had to desolder and resolder 5 of them *oops*
 
NF6X said:
Please forgive me if this has already been discussed, as I arrived late and I have not read the whole thread. Has anybody tested out the XT-FDC with the TestFDC utility from ImageDisk yet? If so, I'm interested in finding out which tests it passed and failed.
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I tested mine, and it passed most of the tests. Next time I get the system up, I'll generate a .txt file with the results and post it here.
 
IMHO pointless... The design uses industry standard FDC controllers (Intel 82077AA or National PC8477B)... They were used before in multiple controller cards and motherboards. The only "custom" hardware parts are address decode and board layout. (The only note is that some Intel parts don't do FM, but that shouldn't be an issue for IBM PC users).

Much more interesting question is testing floppy BIOS for bugs and compatibility :)
 
sergey said:
IMHO pointless... The design uses industry standard FDC controllers (Intel 82077AA or National PC8477B)... They were used before in multiple controller cards and motherboards. The only "custom" hardware parts are address decode and board layout. (The only note is that some Intel parts don't do FM, but that shouldn't be an issue for IBM PC users).

Much more interesting question is testing floppy BIOS for bugs and compatibility :)
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Not pointless, because some of us need to write FM disks for TRS-80 and CP/M use.

Here is my post of opinion of the FDC BIOS:

http://www.vintage-computer.com/vcf...FDC-and-Serial-Port-board&p=341222#post341222
 
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