WELCH@bclcl1.im.battelle.org (Bill Welch (614)424-7155) (07/06/90)
We have noticed that printing to a local printer via the Redirector under PCSA 3.0 is very slow. When sending a large graphic output the time under the redirector was 6 to 7 times slower than going direct to the printer. The following is DEC's response for the record. Has anyone else seen this? What are you doing about it if anything? Couldn't DEC leave A20 enabled once HIMEM.SYS has started or would this possibly break other apps? ...... We have received a response from engineering regarding your problem. It is as follows: The slow printing you are seeing with graphics on the HP Laserjet is because the REDIRector has "hooked" INT 17 and is processing each print request. Each character will require processing by the REDIRector. In the straight DOS case without the REDIRector loaded, the print time is the pure program plus BIOS INT 17 code plus printer latency. When the REDIRector is loaded it must look at each INT 17 request. When the REDIRector is loaded in normal memory each INT 17 request is a couple of subroutine calls to see if the printer is redirected, and if not a chain to BIOS INT 17 code. When the REDIRector is loaded in XMS there is an added overhead on each INT request of saving registers, calling the XMS driver to enable the A20 line, restoring registers, doing the REDIRector checking as above, saving the return registers, calling the XMS driver to disable the A20 line and restoring the registers for return. Enabling and disabling the A20 has a considerable hardware latency adding directly to the overhead of each INT 17 call. The increase in time from one to seven minutes is the added overhead of the REDIRector checking for a redirected printer and the XMS overhead. This increase in time is normally "hidden" with "slow" mechanical actions on local printers. Loading a large graphics file into printer memory with no delays mechanical action accents the added overhead of redirection. This overhead expected and cannot be decreased while maintaining redirection of printers. The best case for a redirected printer and local printing is the REDIRector base memory, not XMS. SUGGESTION Move the REDIRector from XMS to Base Memory when graphic print jobs are to be printed. ----------------------------------------------------------------------------- Bill Welch Internet: WELCH@BCLCL1.IM.BATTELLE.ORG Battelle Memorial Institute Bitnet: WELCH%BCLCL1@OHSTPY 505 King Avenue Packet Radio: W8LLU @ W8CQK.OH.USA.NA Columbus, Ohio 43201 Voice: (614)424-7155 Fax: (614)424-5263