Re: Priam DataTower Pictures

Fantastic work! It would be great to see screenshots of the Priam as recognized by the Office System.

I'm also not clear on how the tape drive was meant to work with LOS---or was it meant to be recognized by the OS at all?

None of the Lisa system software API seems particularly well suited to talking to a tape drive; you could certainly open up a device file in "sequential" mode and stream bytes in and out like on Unix, but given the amount of handholding the OS gives you for other I/O operations, the lack of tape-specific facilities relating to tapes leads me to suspect that this capability was never there to begin with.

Maybe the Data Tower came with its own device drivers and software libraries? Although, Office System was at least bundled with some support, since you could indicate an expansion slot as holding one in Preferences on an out-of-the-box install.

Nice that the interface card has so many post-hoc modifications. Can you tell what they were for?

To echo what you last said: I have working Twiggy drives, and I will gladly back up Twiggies onto modern media with BLU. I'm pretty sure that one of the Workshop 1.0
<http://bitsavers.informatik.uni-stuttgart.de/bits/Apple/Lisa/workshop_1.0/> disks I copied last winter was pretty much on its last legs---these things don't have much time left!

--Tom

On Tuesday, June 16, 2015 at 2:22:50 PM UTC-4, James MacPhail wrote:
>
>
> Hi Folks,
>
> I've posted some quick pics of the Priam DataTower here:
>
> http://www.flickr.com/gp/114907644_at_N04/U9htba
>
> After the struggle to accept the fact that these things actually
> exist, there were 3 challenges with this unit:
>
> 1) There was no interface cable to connect the DataTower to the Lisa.
> Disassembling the EPROM and reverse engineering the Lisa interface
> card, reviewing the documentation (many thanks to BitSavers) for
> various Priam controllers, and examining the driver/receiver
> combinations at the two ends resulted in a probable cable pinout,
> which seems to work.
>
> 2) Once it was able to communicate, the controller was reporting that
> the RAM self-test failed. The controller uses an 8088 family
> microprocessor, so it was possible to trace the self-test with a
> logic analyzer to observe the point of failure. The problem turned
> out to be that when writing to the RAM, the write signal remained
> asserted well after the address lines were no longer valid, and so
> unintentional changes were being made to semi-random RAM locations.
> In this state it could never have passed the self-test, yet the
> controller appears fully operational aside from this write timing
> problem. As it is unknown as to whether this controller ever worked,
> only a minor attempt was made to determine if some component had
> failed in a way that produced this subtle change. Instead, a
> modification was made to properly terminate the RAM's write signal
> while the address is still valid.
>
> 3) Once the controller was able to pass the self-test, the drive
> would unlock and spin up, but then time out. After studying
> schematics and theory of operation for other Priam drives, and
> substantial hours of troubleshooting, it was determined that two
> parts had failed on the servo board. The parts were IH5052 analog
> switches (similar to the 4066 and apparently the only CMOS parts in
> the unit, which are much more fragile than TTL parts). After
> replacing these with currently available equivalents, the drive
> operates correctly.
>
> It remains to be seen whether the tape drive is able to read/write
> properly, but it does rewind and re-tension on demand. A large part
> of the challenge here is fixing up DC-600A tapes so that they spool
> properly again.
>
> James
>
> PS. For those of you with any uncommon Twiggy floppy disks, please
> back them up before they deteriorate further! If you have working
> Twiggy drives, you can use BLU to do this; feel free to ask for help.
> If you don't have working Twiggy drives, there are a few people who
> have a working Lisa 1 that will be happy to assist. If you are a
> collector, consider that a rare or one-of-a-kind original disk is not
> going to be worth so much if it is just a label on an unreadable disk
> and no-one can find the software it represents.
>

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