Was WD1772 obsolete in 1985 ?

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Petari
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Was WD1772 obsolete in 1985 ?

Post by Petari » Sat Jun 02, 2018 12:28 pm

I needed little repair on my Mega STE - floppy became extremely unreliable, so looked some things online, because really forgot even pin layouts and other things. Spotted this on Best Electronics site, where they sell Atari chips and related stuff. At bottom of page
http://www.best-electronics-ca.com/custom-i.htm#Ajax

" Obsolete WD1772 Chip
Years down line when the newer Atari MegaSTE and Atari Falcon computers were being designed, the old WD1772 chips were becoming obsolete. Most Disk Controller chips of that era, were lucky to have a normal useful product life / run of 1 to 2 years at most. Atari had been using the WD1772 Floppy Disk Controller chip in ST computers close to 7+ years. Western Digital had not made any new production runs of WD1772 Disk Controller chips in years and could not be convinced to make a new run of that old Disk Controller chip. To support the older Atari ST computer line, Atari had the VLS Chip Company get a license from Western Digital and make a small new production run of the older standard WD1772 Disk Controller chip in a VLS labeled chip package for Atari. "

I think that it is just not correct. I seen same Intel FDC chip in PCs over many years. Only real flaw of WDC 1772 is low pin number, so there is no drive select, side select, and it needs other chip(s) for that (what in case of ST is sound chip (with it's parallel ports) . WDC is better in some things than Intel FDC chip in PCs - it's faster - for instance will detect sector closer to index pulse. You may test it, if format floppy with Fast Copy Pro with some fast flag on. There are some minor bugs in 1772 - in track read in first place, but that was never used in regular work, only in copy protections.

"
But the writing was on the wall. Atari Engineering had to find a new ST Disk Drive Controller chip and do some ST Major chip set changes or whole new redesign on future Atari ST Computers in regards to the ST Floppy Circuit design. What Atari Engineering came up with was a new custom made Upgraded / Smart Disk Controller chip which was backward and forward compatible on all older ST computers and fully compatible on Falcon computers and future ST computers. That new smart chip is the Atari Ajax High Speed Floppy Disk Controller chip.
Ajax Chip
The New Atari Custom made Ajax Disk Controller chip is 100% pin to pin fully backward compatible with the older WD1772 chip on all older ST and other Computer and devices that use the WD1772 Floppy Disk Controller chip. It is also a Smart Disk Controller Chip that can auto sense the input chip Mhz Clock speed and auto switch into the Newer HD 1.44 Floppy Mode standard. So a new state of the art Atari Ajax Disk Controller chip can be plugged into the first 1985 Atari 520ST computer made and drive the ST 720K SSSD / DSDD floppy internal or external Disk drive Mech. The same exact Atari Ajax chip can be plugged into the Floppy Disk circuit on the last state of the art Atari ST computer made, the 1992 Falcon 030 68000 16Mhz Computer and drive the Falcon 1.44 HD Floppy Circuit without any hardware changes."

Utter BS. They have no clue what talking about. Smart Disk Controller - LOL ! :WTF: And on top of it, they knew that it is 100% pin to pin same with regular 1772 - so where is then pin for detecting floppy density ? Where is internal clock switch ? If that would be true, it should get always 16 MHz clock, and then internally divide it to 8 when work in DD mode. Just a stupid, irresponsible blah.
The truth is that there is extra (PAL) chip in Mega STE, what changes clock for FDC chip - 8 MHz for DD, 16 MHz for HD, according to disk density line state. And all HD upgrades for ST(E) work on same principle. Then, about half of regular 1772 chips can work at 16 MHz. Of course, Best will not tell you it, they need to sell ...

The truth is that Ajax is simply WD1772 made for stable work at 16 MHz .
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

troed
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Re: Was WD1772 obsolete in 1985 ?

Post by troed » Sat Jun 02, 2018 1:41 pm

MSTE doesn't use disk density signals to select clock. Basically it just tries both and sees which mode works ..

Petari
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Re: Was WD1772 obsolete in 1985 ?

Post by Petari » Sat Jun 02, 2018 2:46 pm

But density line from floppy is used, and goes to PAL chip - look schematic. Possible that there are diverse revisions.
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

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frank.lukas
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Re: Was WD1772 obsolete in 1985 ?

Post by frank.lukas » Sat Jun 02, 2018 2:56 pm

AJAX can also work fine in ED mode with 32Mhz ...

troed
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Re: Was WD1772 obsolete in 1985 ?

Post by troed » Sat Jun 02, 2018 5:11 pm

Petari wrote:
Sat Jun 02, 2018 2:46 pm
But density line from floppy is used, and goes to PAL chip - look schematic. Possible that there are diverse revisions.
There's no density output from the Epson 340 :)

See this thread: http://www.atari-forum.com/viewtopic.ph ... 19#p113215

Petari
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Re: Was WD1772 obsolete in 1985 ?

Post by Petari » Sat Jun 02, 2018 6:03 pm

OK, OK, I believe you about that try and change mode. I just said what is on schematic.
I spent half day with this, what is now really so-so obsolete, and unreliable - when 80 % of drives and disks is broken, you start to seek error in computer. Well, there is still no error - thanx God. I just soldered PAL density input to high level, and will not bother to even check is HD mode working or not .
Need floppy only for rare cases, and as I finish Virtual Floppy, it will be once in decade, so never anymore - 10 years from now %-e will be 99% = broken - so better not risk heart attack :lol:

Anyone needs good Ajax chip ?
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

troed
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Re: Was WD1772 obsolete in 1985 ?

Post by troed » Sat Jun 02, 2018 6:19 pm

Petari wrote:
Sat Jun 02, 2018 6:03 pm
OK, OK, I believe you about that try and change mode. I just said what is on schematic.
Well I agree pin 2 is connected to the PAL, but I can only assume that's an output. Epson 340 does take density select as an _input_ on pin 2.

http://floppy.shugart.free.fr/docs/epso ... smd340.pdf

(I think this was a quite interesting find even though I agree with you that floppy users are getting fewer and fewer ... ;))

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frank.lukas
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Re: Was WD1772 obsolete in 1985 ?

Post by frank.lukas » Sat Jun 02, 2018 9:02 pm

With a HD-Modul for a ST machine Shugart Pin2 must be an Output on the Floppy. on a Mega STE, Falcon, Atari TT or a PC is the Shugart Pin2 on a Floppy a Input.

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