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  Message 1 of 5  
15 Jul 17 04:40
prabhakar vinayagam
xxxxxx@gmail.com
Join Date: 29 Jan 2016
Posts To This List: 82
when enable "c" states , COM port were not worked at high baudrate

Hi all, When i disable the "c" states in bios side , com port detected the "receive buffer overrun " in windows 10. When i enable the "c" states in bios side, cpu is not enter into acpi c states if the com port used high baudrate to do data transfer in windows 10 where it used the inbox driver. It uses the pnpo500 pnp pc device. How i can fix this issue in windows sample driver 10 of serenum to check the driver enter into acpi c states to fix it were working in high baudrate ? when i check in PassMark where com port detected the receive buffer overrun. Could you please help on this issue to fix in windows sample driver for serial port. Regards, Prabhakar V
  Message 2 of 5  
16 Jul 17 17:33
Pavel A
xxxxxx@fastmail.fm
Join Date: 21 Jul 2008
Posts To This List: 2389
when enable "c" states , COM port were not worked at high baudrate

Maybe this is because PassMark does not support very high speed serial ports well. Look for more specialized benchmark for serial I/O. Good design of the driver probably can help too, because C states interfere with latency of interrupt handling. A custom driver for your device can do interrupt moderation or even disable C states on the CPU it runs on. Be creative, try to think out of the box :) -- pa
  Message 3 of 5  
16 Jul 17 20:50
Peter Viscarola (OSR)
xxxxxx@osr.com
Join Date:
Posts To This List: 5906
List Moderator
when enable "c" states , COM port were not worked at high baudrate

Didn't we already see this post... like, last week? Peter OSR @OSRDrivers
  Message 4 of 5  
17 Jul 17 02:35
prabhakar vinayagam
xxxxxx@gmail.com
Join Date: 29 Jan 2016
Posts To This List: 82
when enable "c" states , COM port were not worked at high baudrate

when enable "c" states , COM port were not worked at high baudrate [Peter ]Didn't we already see this post... like, last week?' [Prabhakar] yes i have posted already but i need to see that when we enable the c states in bios side , it were working for high baudrate. What will be the impact when we enable the c states it doesn't work for high baudrate in windows 10 where showing receive buffer overrun in inbox driver. What will be imapct when we enable the c states it doesnt work ? What i have to do in windows sample driver code and fix this error? if we disbale it is working for high baudrate in passmark tool.
  Message 5 of 5  
17 Jul 17 02:47
Tim Roberts
xxxxxx@probo.com
Join Date: 28 Jan 2005
Posts To This List: 11533
when enable "c" states , COM port were not worked at high baudrate

On Jul 16, 2017, at 11:35 PM, xxxxx@gmail.com xxxxx@lists.osr.com wrote: > > when enable "c" states , COM port were not worked at high baudrate > [Peter ]Didn't we already see this post... like, last week?' > [Prabhakar] yes i have posted already but i need to see that when we enable the c states in bios side , it were working for high baudrate. > > What will be the impact when we enable the c states it doesn't work for high baudrate in windows 10 where showing receive buffer overrun in inbox driver. > > What will be imapct when we enable the c states it doesnt work ? > What i have to do in windows sample driver code and fix this error? > if we disbale it is working for high baudrate in passmark tool. What are you expecting here? The answers are not going to change. As I have tried to tell you in public and in private, there is no magic answer here. The slowed down CPU can't get around to service your interrupt before the hardware FIFO fills. So, you either turn off the use of C states, you change the level at which you get the interrupt, or you configure a larger buffer. That's it. There are no other choices. That means you need to know your hardware, to know how the FIFOs are configured. I don't think you know that yet. — Tim Roberts, xxxxx@probo.com Providenza & Boekelheide, Inc.
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