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So, not to get TOO off-topic in my own thread, but I now have one of the AT88-S1PD drives, so a few questions maybe someone can answer.

 

Instead of the 1.21 firmware, to have the "best one" I should use the >1.21 firmware, correct?  Phaeron, do you have a disassembly for this one?

 

I ask about the disassembly because I plan to work on it.  At 4K with plenty of free space, it should be possible - I think - with a lot of 6809 coding and work, and testing, to add new SIO commands, "Happy-like" drive functionality, high speed support, etc.  At least the hardware should be able to support it, if someone writes all the necessary code, is this correct.  I'm willing to give it a try, at the very least.  If I could start with an annotated disassembly, at least I wouldn't have to start completely from scratch.

 

Also - how do I make a printer cable for this?  Is it just a matter of 34pin ribbon cable, 34 pin header on one end, and a 36(?) pin Centronics connector on the other?  Or is there more to it than that?  I can make the cable, but I'll need to order the Centronics connector, and I'm not sure exactly how to make one.  The connectors are not exactly cheap, so advice here would help me before I screw it up and waste connectors.

 

Thanks in advance for any help on this stuff.  I've never owned one of these particular drives, and this one came to me broken, but I fixed it.  I'd like to be able to use it to it's full potential.

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2 hours ago, glurk said:

So, not to get TOO off-topic in my own thread, but I now have one of the AT88-S1PD drives, so a few questions maybe someone can answer.

 

Instead of the 1.21 firmware, to have the "best one" I should use the >1.21 firmware, correct?  Phaeron, do you have a disassembly for this one?

Two posts down in same thread: https://atariage.com/forums/topic/304384-percom-at-88-doubler-rom/?do=findComment&comment=4502829

 

2 hours ago, glurk said:

I ask about the disassembly because I plan to work on it.  At 4K with plenty of free space, it should be possible - I think - with a lot of 6809 coding and work, and testing, to add new SIO commands, "Happy-like" drive functionality, high speed support, etc.  At least the hardware should be able to support it, if someone writes all the necessary code, is this correct.  I'm willing to give it a try, at the very least.  If I could start with an annotated disassembly, at least I wouldn't have to start completely from scratch.

It does have a lot of free ROM space. However, the hardware only has 1K of RAM, so it can't do track buffering, and the UART clock is hardwired. Most other drives bit-bang the SIO bus in software, so to implement high-speed mode you just need a tighter transfer loop. Not so with the Percom drives, they simply read or write bytes from the UART. As far as I know none of the Percom drives are capable of supporting US Doubler style high speed operation without hardware modifications. Probably the most useful change would be to add enhanced density support.

 

The Percom firmware also lacks the ability to upload code to the drive. However, I've long suspected that it may be possible to do so by overflowing the sector buffer, since it doesn't check the parameters for the Write PERCOM Block command and the sector size is a 16-bit int. Unfortunately, I don't have a physical drive to test this.

 

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9 hours ago, glurk said:

So, not to get TOO off-topic in my own thread, but I now have one of the AT88-S1PD drives, so a few questions maybe someone can answer.

 

Instead of the 1.21 firmware, to have the "best one" I should use the >1.21 firmware, correct?  Phaeron, do you have a disassembly for this one?

 

I ask about the disassembly because I plan to work on it.  At 4K with plenty of free space, it should be possible - I think - with a lot of 6809 coding and work, and testing, to add new SIO commands, "Happy-like" drive functionality, high speed support, etc.  At least the hardware should be able to support it, if someone writes all the necessary code, is this correct.  I'm willing to give it a try, at the very least.  If I could start with an annotated disassembly, at least I wouldn't have to start completely from scratch.

 

Also - how do I make a printer cable for this?  Is it just a matter of 34pin ribbon cable, 34 pin header on one end, and a 36(?) pin Centronics connector on the other?  Or is there more to it than that?  I can make the cable, but I'll need to order the Centronics connector, and I'm not sure exactly how to make one.  The connectors are not exactly cheap, so advice here would help me before I screw it up and waste connectors.

 

Thanks in advance for any help on this stuff.  I've never owned one of these particular drives, and this one came to me broken, but I fixed it.  I'd like to be able to use it to it's full potential.

I don't recall every using a two drive Percom now that I think about it.  So I may have acquired this manual and controller board from a dead system.  Possibly from

a friend?  Anyway, here are a few pics of the board(s).  The smaller daughter board plugs into the U6 socket.  The ROM chip is labeled, 'AT88 V1.3'.  Also of note is

that the three voltage regulators (Q1,Q2, Q3) are all soldered on the bottom of the CB and are tapped for fine thread screws.  If anyone wants I can dump the ROM

chip?

 

DavidMil

AT88 Controller Board.JPG

AT88 Daughter Board.JPG

Controller Board Disassembled .JPG

AT88 ROM .JPG

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On 9/30/2021 at 1:43 AM, DavidMil said:

The smaller daughter board plugs into the U6 socket. 

This would be the PERCOM AT88-DDA(double-density adapter board), I have a single-density AT88-S1 that has a DATA separator board instead.

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My AT88-S1PD also has the regulators tapped for screws.  Which is really weird, since it turns a commodity easily-replaced part into a specialized hard-to-replace one.  I don't have a tap and die set just lying around...

 

And what the heck is the difference between the AT88-S1PD and the AT88-SPD?  Is it just a naming difference or somethings else?

 

And I'm still trying to figure out how to make a printer cable to attach a printer to one of these, if only just to be able to TEST it.

 

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As far as I know, the AT88-S1PD and AT88-SPD are the same, with the SPD being the generic name for the base hardware and the S1PD being the specific configuration with one disk drive. The -SPD name is referenced in some of Percom's literature, particularly the schematic. This schematic matches all 4K printer capable firmware images that have been dumped from S1PD drives. This is similar to RFD40-S1/S2/RFD44-S1/S2 also being the same base hardware and firmware with different drive configurations.

 

Additionally, we have some evidence from circuit boards of the AT88 having been called internally RFD II.

 

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On 9/30/2021 at 7:41 AM, MrFish said:

 

I think that would be a good idea.

 

Well; I'm a little embarrassed now.  When I popped the EPROM out and put it in my reader and dumped it, it's just full of FF's.  Someone must have wiped it

clean.  I'm very sorry.  I looked on my DOS computer but couldn't find any reference to the chip.  Once again I apologize, but at least we know that there is

a version 1.3 out there somewhere...

 

David

 

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26 minutes ago, DavidMil said:

Well; I'm a little embarrassed now.  When I popped the EPROM out and put it in my reader and dumped it, it's just full of FF's.  Someone must have wiped it

clean.  I'm very sorry.  I looked on my DOS computer but couldn't find any reference to the chip.  Once again I apologize, but at least we know that there is

a version 1.3 out there somewhere...

 

No sweat. No baby kittens were harmed in the process.

 

We're already aware of a 1.3 and 1.4, and it isn't clear that the ">1.21" ROM isn't actually v1.3. Having a dump of your ROM would have answered that question, though.

 

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It would hurt to try to read that again some other time or with a different reader or method... it wouldn't be the first time something was thought to be empty and wasn't...

Don't sweat it.

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6 hours ago, _The Doctor__ said:

It would hurt to try to read that again some other time or with a different reader or method... it wouldn't be the first time something was thought to be empty and wasn't...

Don't sweat it.

Bad News:     Checked it again and even cleaned up the legs with some 400 grit sand paper but still getting FF's.

Good News:   I looked on several 3.5 floppy disks and I found this file from earlier this year.  I'm not going to

guarantee it, but it MAY be the same chip...

 

DavidMil

AT88V13.BIN

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2 hours ago, DavidMil said:

Bad News:     Checked it again and even cleaned up the legs with some 400 grit sand paper but still getting FF's.

Good News:   I looked on several 3.5 floppy disks and I found this file from earlier this year.  I'm not going to

guarantee it, but it MAY be the same chip...

 

DavidMil

AT88V13.BIN 2 kB · 3 downloads

 

It doesn't match any hash that I have; and it doesn't match the first 2 KB of the ">1.21" version by file compare. So, whatever it is, it looks to be a unique dump.

 

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There's only one very small difference between AT-88 V1.2 and V1.30: the formatted data for double-density sectors was changed from $9249 to $0000. Strangely, single density wasn't also fixed. This issue wasn't fixed in the other product lines until RFD 2.10.

 

AT88 and AT88SPD firmwares don't match up; there are significant hardware differences and the printer code was also inserted near the beginning of the firmware, so they'll never appear similar in any significant way unless you compare them by procedures instead of byte offsets.

 

Incidentally, the AT88-SPD V1.01 dump above corresponds to a previously discovered incomplete listing, which had everything except the end padding and interrupt vectors. We had been able to determine that it was the oldest known revision by the lack of bug fixes from later versions, but now we specifically know what version it is.

 

 

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