porter@IAGO.CALTECH.EDU (Mark Andrew Porter) (04/30/87)
At JPL, we had the need to read a 9600 baud line from a brain-damaged
computer called a Varian. The Varian has no clue about flow-control of
any type. We needed to read this line with a Microvax II running
VMS 4.5. At first, we had problems with small type-ahead buffers
causing overflows. Then we found the disk drive wasn't fast enough
at extending files. So we went to using a Pseudo-disk (PDA0:).
It should be noted that this was only MINIMALLY faster... VAX
memory is truly virtual... *smile*
However, when we got a faster disk drive, we found out a way to do the
transfer with no overflow problems whatsoever:
1. Set TTY_ALT_TYPEAHEAD (or whatever) to a large number. We used
10240.
2. Don't forget to changed MAX_BUFFER (or whatever) to the same large
number. Otherwise AUTOGEN will ignore the TTY_ALT_TYPEAHEAD number.
3. Create a huge file on your disk drive with CREATE/FDL. We found
that our "data overrun" error was occuring every time that the
file needed to be extended. We also set the EXTEND value large.
4. Copy the file over.
5. COPY/TRUNCATE the file to remove the huge disk allocation.
Hope this solves your problem. We have found that both the typeahead
buffer and the large file creation must be used in order to have
reliable performance.
Mark Porter Porter@CitJulie.Bitnet
M/S 189 Porter@Juliet.Caltech.Edu
Jet Propulsion Lab Porter@Jpl-Vlsi.Arpa
Pasadena, Ca
(818) 792-3711