12 Jan
2006
12 Jan
'06
2:46 p.m.
Chuck Guzis wrote:
On 1/12/2006 at 1:47 PM jim stephens wrote:
All of the Overland controllers had a good news / bad news way of
handling the transfer rate. They
had memory buffers on the board. The only one that did not have direct
access was the PC-50, which
would not work that well for anything but older 800 bpi drives.
The problem that I saw was on a PCI board, which had on board buffers,
and a microprocessor
that Overland included to assist in processing. It was not used for the
software i had, nor do I know
what software used it (TXI). I believe that the data was buffered into
a dual port memory before
reading it out.
I'll have to check the specs to see what it was rated for.
The problem I had was that most times there was no reaction from the
drive after the first record
was transfered. There seemed to be motion from the BOT over the first
record, then nothing.
I don't recall the signals to name what was missing, but there appeared
to be a lack of reaction
by the drive after the first record completed. I did not have any luck
figuring it out as I didn't have
that detailed a manual for the drive at the time to use to troubleshoot.
Jim
PCI/ISA includes Overland Data if you can find the
controller. I had
trouble running the 2444 on the Overland TXI, so be warned on that.
The M2444AC has a bit more intelligence that you'd otherwise expect. For
one, it does a lot of buffering, so the data transfer rate (from first byte
to the last) is exactly the same for 1600 as it is for 6250. And that's
the maximum 1.1MHz that the Pertec interface is rated for. Many simple ISA
interface cards have trouble doing a sustained transfer at this rate. The
high-end ones with local buffering should handle things a bit better.
When a Pertec-interface drive is reading, there's no handshake for data
transfer to the host--the drive simply puts the data on the read lines and
pulses a strobe line--you're expected to be there to catch it. Other than
the data transfer issues, a Pertec interface is a very simple thing and you
could probably work up your own interface without too much difficulty.
Cheers,
Chuck