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  Message 1 of 10  
08 Jan 17 22:10
Zvi Vered
xxxxxx@gmail.com
Join Date: 27 Dec 2016
Posts To This List: 14
64bits windows vs. 32bits windows: access to PCIe

Hello, From what I know, access to DDR is faster with 64bits windows O.S compared to 32bits windows O.S Is this true also for PCIe memory mapped registers accessed from a device driver ? Thank you, Z.V
  Message 2 of 10  
09 Jan 17 11:48
Tim Roberts
xxxxxx@probo.com
Join Date: 28 Jan 2005
Posts To This List: 11258
64bits windows vs. 32bits windows: access to PCIe

On Jan 8, 2017, at 7:09 PM, xxxxx@gmail.com wrote: > > From what I know, access to DDR is faster with 64bits windows O.S compared to 32bits windows O.S Where did you read that? I don't believe it. DDR is hardware. It doesn't care what the operating system is. There might be some gain in reading a 64-bit word with one instruction instead of two 32-bit reads, but that's slight. > Is this true also for PCIe memory mapped registers accessed from a device driver ? No. Even if it were true, so what? It is what it is. — Tim Roberts, xxxxx@probo.com Providenza & Boekelheide, Inc.
  Message 3 of 10  
09 Jan 17 21:07
Zvi Vered
xxxxxx@gmail.com
Join Date: 27 Dec 2016
Posts To This List: 14
64bits windows vs. 32bits windows: access to PCIe

Hi Tim, Here is what I found in: https://support.microsoft.com/en-us/help/15056/windows-7-32-64-bit-faq#1TC=window s-7 "The benefits of using a 64-bit operating system are most apparent when you have a large amount of random access memory (RAM) installed on your computer, typically 4 GB of RAM or more. In such cases, because a 64-bit operating system can handle large amounts of memory more efficiently than a 32-bit operating system, a 64-bit system can be more responsive when running several programs at the same time and switching between them frequently" I'm aware 64-bit O.S can handle more than 4GB RAM. But if I have 2 PCs, both have 3GB RAM, will the 64bit windows in PC-1 work faster that 32bit windows in PC-2 ? Thank you, Z.V
  Message 4 of 10  
09 Jan 17 22:18
Peter Viscarola (OSR)
xxxxxx@osr.com
Join Date:
Posts To This List: 5753
List Moderator
64bits windows vs. 32bits windows: access to PCIe

Actually, I would bet the 64-bit system with just 3GB would be slower tha the 32-bit syste, with 3GB. But... it depends on exactly what you mean by "work faster"... Peter OSR @OSRDrivers
  Message 5 of 10  
09 Jan 17 23:33
Tim Roberts
xxxxxx@probo.com
Join Date: 28 Jan 2005
Posts To This List: 11258
64bits windows vs. 32bits windows: access to PCIe

On Jan 9, 2017, at 6:05 PM, xxxxx@gmail.com wrote: > > Here is what I found in: > https://support.microsoft.com/en-us/help/15056/windows-7-32-64-bit-faq#1TC=window s-7 > > "The benefits of using a 64-bit operating system are most apparent when you have a large amount of random access memory (RAM) installed on your computer, typically 4 GB of RAM or more. In such cases, because a 64-bit operating system can handle large amounts of memory more efficiently than a 32-bit operating system, a 64-bit system can be more responsive when running several programs at the same time and switching between them frequently" And you know what that means, right? It means that the 64-bit system can USE that memory beyond 4GB, whereas the 32-bit system can't. This is NOT saying that 64-bit systems are faster when accessing the same memory. > But if I have 2 PCs, both have 3GB RAM, will the 64bit windows in PC-1 work faster that 32bit windows in PC-2 ? No. In fact, it works slower, because the average instruction size is larger (because your constants and relocation addresses are twice as big), and that means you can only fit half as many instructions in the caches. — Tim Roberts, xxxxx@probo.com Providenza & Boekelheide, Inc.
  Message 6 of 10  
10 Jan 17 18:12
M M
xxxxxx@hotmail.com
Join Date: 21 Oct 2010
Posts To This List: 675
64bits windows vs. 32bits windows: access to PCIe

On the other hand, the x64 calling conventions and other ABI improvements might make certain kinds of code run faster None of this has anything to do with the speed with which data can be read from RAM Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Tim Roberts<mailto:xxxxx@probo.com> Sent: January 9, 2017 11:32 PM To: Windows System Software Devs Interest List<mailto:xxxxx@lists.osr.com> Subject: Re: [ntdev] 64bits windows vs. 32bits windows: access to PCIe On Jan 9, 2017, at 6:05 PM, xxxxx@gmail.com wrote: > > Here is what I found in: > https://support.microsoft.com/en-us/help/15056/windows-7-32-64-bit-faq#1TC=window s-7 > > "The benefits of using a 64-bit operating system are most apparent when you have a large amount of random access memory (RAM) installed on your computer, typically 4 GB of RAM or more. In such cases, because a 64-bit operating system can handle large amounts of memory more efficiently than a 32-bit operating system, a 64-bit system can be more responsive when running several programs at the same time and switching between them frequently" And you know what that means, right? It means that the 64-bit system can USE that memory beyond 4GB, whereas the 32-bit system can't. This is NOT saying that 64-bit systems are faster when accessing the same memory. > But if I have 2 PCs, both have 3GB RAM, will the 64bit windows in PC-1 work faster that 32bit windows in PC-2 ? No. In fact, it works slower, because the average instruction size is larger (because your constants and relocation addresses are twice as big), and that means you can only fit half as many instructions in the caches. ? Tim Roberts, xxxxx@probo.com Providenza & Boekelheide, Inc. --- NTDEV is sponsored by OSR Visit the list online at: <http://www.osronline.com/showlists.cfm?list=ntdev> MONTHLY seminars on crash dump analysis, WDF, Windows internals and software drivers! Details at <http://www.osr.com/seminars> To unsubscribe, visit the List Server section of OSR Online at <http://www.osronline.com/page.cfm?name=ListServer> --
  Message 7 of 10  
11 Jan 17 11:20
Zvi Vered
xxxxxx@gmail.com
Join Date: 27 Dec 2016
Posts To This List: 14
64bits windows vs. 32bits windows: access to PCIe

Hello Tim, Peter, Thank you very much for your replies. Best regards, Z.V
  Message 8 of 10  
11 Jan 17 17:43
Pavel A
xxxxxx@fastmail.fm
Join Date: 21 Jul 2008
Posts To This List: 2329
64bits windows vs. 32bits windows: access to PCIe

> Is this true also for PCIe memory mapped registers accessed from a device driver ? The root complex packs memory access requests into PCIe transport layer messages (TLPs or whatever). So if it can pack a 64-bit request in one message instead of two 32-bit messages, there will be performance gain. If you have a PCIe analyzer, look what goes on the bus when you call WRITE_REGISTER_BUFFER_ULONG64 vs. WRITE_REGISTER_BUFFER_ULONG. -- pa
  Message 9 of 10  
11 Jan 17 20:22
Tim Roberts
xxxxxx@probo.com
Join Date: 28 Jan 2005
Posts To This List: 11258
64bits windows vs. 32bits windows: access to PCIe

On Jan 11, 2017, at 2:41 PM, xxxxx@fastmail.fm wrote: > >> Is this true also for PCIe memory mapped registers accessed from a device driver ? > > The root complex packs memory access requests into PCIe transport layer messages (TLPs or whatever). So if it can pack a 64-bit request in one message instead of two 32-bit messages, there will be performance gain. If you have a PCIe analyzer, look what goes on the bus when you call WRITE_REGISTER_BUFFER_ULONG64 vs. WRITE_REGISTER_BUFFER_ULONG. Many of the root complex controllers are able to combine sequential write cycles into one longer packet, but that doesn't help on a read. — Tim Roberts, xxxxx@probo.com Providenza & Boekelheide, Inc.
  Message 10 of 10  
12 Jan 17 12:50
Pavel A
xxxxxx@fastmail.fm
Join Date: 21 Jul 2008
Posts To This List: 2329
64bits windows vs. 32bits windows: access to PCIe

> Many of the root complex controllers are able to combine sequential write cycles into one longer packet, but that doesn't help on a read. Yes, another iteration of the "write buffer" of PCI era. Reads flush the write buffer. Unfortunately the sniffer is expensive and I don't have it around all the time. Would like to see trace of READ_REGISTER_BUFFER_ULONG64 vs. READ_REGISTER_BUFFER_ULONG. -- pa
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