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32-bit os 6GiB or 24GiB ram

Last response: in Windows 7
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July 8, 2010 5:05:42 AM

I am thinking of buying a new machine with windows 7. I need to do DOS development. only 32-bit OS's come with command.com which is required for doing DOS development.
I have to choose between a motherboard with a lesser processor and 4GiB dual-channel ram or a triple-channel architecture system that has 6GiB ram or more.

1. my understanding is that the definition of 32-bit OS is that it can only access 4GiB of ram and it is MBR+BIOS based which also has a 32-bit limitation, but not limited to 2GiB disk size due to cluster sizes. My concern is the memory. is this true for 7? I currently have 32-bit XP on an old P4.

2. Has anyone ever gotten xp mode to work with an OEM windows 7 pro?

3. can I use a triple-channel mb with 6GiB ram with 32-bit 7?

More about : bit 6gib 24gib ram

a b $ Windows 7
July 8, 2010 5:18:55 AM

I can't even begin to understand what your asking in part one. We haven't been limited to 2gb disks for quite some time. If your running a 32bit windows os your limited to 4GBs total. You should have around 3.25 available unless your running CF/SLI. Because of this I wouldn't bother with 6GBs or higher. I'm also trying to understand why your getting a huge i7 system if your just programing dos. Get a cheap older system and be done with it. As for 32bit vs 64bit can you use Dosbox or something like that?

2) Win 7 home premium doesn't officially come with XP mode, though there are hacks to make it work. All versions higher then HP come with XP mode. Whether its OEM or retail shouldn't matter. (not that I've heard anyways.)

3) You can, but see point one above. Why buy 6GBs worth if you'll only have 3.25GB to use? There is so much about this post that I don't understand.
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a b $ Windows 7
July 8, 2010 5:28:08 AM

Learn all about XP mode. http://www.microsoft.com/windows/virtual-pc/default.asp...

There are lots of people using it, it makes no difference being an OEM disk, but you must specify 64 bit when buying an OEM version as only one or the other is supplied, the retail pack contains both 32 bit and 64 bit.

6 GB on a 32 bit system (XP, Vista, W7 makes no difference) is a waste as you would not be able to use more then about 3.5 GB or even less.
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a c 209 $ Windows 7
July 8, 2010 5:39:14 AM

32-bit Vista and Windows 7 can only access a little less than 4GB of memory (4GB less the memory aperture used by your video card and other I/O devices).

32-bit operating systems do not place a limit on disk capacity. NTFS, the default file system for Windows, can handle disks of up to exabytes in size even for 32-bit versions. The only restriction is on how large a disk you can BOOT from, see: http://en.wikipedia.org/wiki/GUID_Partition_Table#Windo....

You didn't say what kind of DOS development you're doing, but you could consider running a 64-bit OS with either a DOS emulator (DOSBox, for example) or a copy of XP running in a virtual machine.
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July 8, 2010 6:25:12 AM

simply... NOO you cannot use triple channle 6gb (3x2gb) with win 7 32bit.
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a c 209 $ Windows 7
July 8, 2010 6:51:38 AM

lowriderflow said:
simply... NOO you cannot use triple channle 6gb (3x2gb) with win 7 32bit.
Well you can run with it - the system will work just fine with that much memory installed. It just won't be able to actually use all of it.
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July 8, 2010 3:30:42 PM

jmichae3 said:
1. my understanding is that the definition of 32-bit OS is that it can only access 4GiB of ram and it is MBR+BIOS based which also has a 32-bit limitation, but not limited to 2GiB disk size due to cluster sizes. My concern is the memory. is this true for 7? I currently have 32-bit XP on an old P4.


A 32-bit OS can access up to 64GB of RAM (or is it 128GB?) on an x86 CPU, but Microsoft only allow you to access 4GB of that in desktop versions of Windows. And in any case each 32-bit application can only see about 3GB of that memory.

I believe the limitation you're thinking of is the 32-bit MBR counters which limit a partition to 2TB with 512-byte sectors (2^32 sectors x 512 bytes). That's a filesystem limitation rather than a CPU limitation, and on drives which support 4k sectors properly you can go to 16TB before it becomes impossible to work around.

The only reason I can see not to run 64-bit Windows is if you want to run old 16-bit applications, which it simply can't do without using an emulator. That said, given that almsot all Windows applications are still 32-bit, they won't be able to access more than 4GB of RAM even on a 64-bit OS; if you were running Linux, where pretty much every application is native 64-bit, I'd say there's no reason at all to run a 32-bit OS.
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a b $ Windows 7
July 8, 2010 4:22:26 PM

Quote:
A 32-bit OS can access up to 64GB of RAM (or is it 128GB?) on an x86 CPU, but Microsoft only allow you to access 4GB of that in desktop versions of Windows.


How do you figure? 2^32 ~ 4GB. How do you get 64GB or higher out of that? A 32 bit OS would have 32 memory registers, so it would only be able to handle 4GBs. Not counting PAE or other memory mapping tricks.
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a b $ Windows 7
July 8, 2010 4:41:29 PM

MarkG said:
A 32-bit OS can access up to 64GB of RAM (or is it 128GB?) on an x86 CPU, but Microsoft only allow you to access 4GB of that in desktop versions of Windows. And in any case each 32-bit application can only see about 3GB of that memory.


It's a physical limitation, not one created by microsoft. A 32-bit OS uses an addressing method with a binary length of 32 digits. That roughly equals 4 GBs (like 4745454b stated above).
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July 8, 2010 5:50:04 PM

4745454b said:
How do you figure? 2^32 ~ 4GB. How do you get 64GB or higher out of that? A 32 bit OS would have 32 memory registers, so it would only be able to handle 4GBs. Not counting PAE or other memory mapping tricks.


PAE is the feature that allows the OS to access that memory. Each application can only have 4GB but the OS can share the 64GB among the various applications.

And while it's a kludge, it's essentially the same situation as 64-bit Windows running 32-bit applications as they can't access more than 4GB each either.

But, as mentioned, Microsoft refuse to support PAE on desktop versions of Windows, so you're stuck with a 4GB limit there unless you run 64-bit.
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a c 209 $ Windows 7
July 8, 2010 8:23:06 PM

MarkG's right - 32-bit Windows Server systems have long been able to access memory beyond the 4GB barrier by using PAE-enable hardware (PAE=Physical Address Extensions) combined with the AWE (Address Windowing Extensions) API for those applications that wanted to use more than 3GB of memory (typically server apps like SQL). It's a kludge, but it has been possible.

However now that we're in the era of 64-bit operating systems that's an anachronism and isn't really a point worth considering, IMHO.
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a b $ Windows 7
July 8, 2010 11:45:30 PM

Thats why I mentioned it. There are work arounds, but they tend to suck. Mark came in and "blasted" MS indicating its their fault that 32bit windows is limited to 4GBs of ram. Because they don't include support for some "crazy" memory scheme doesn't really make it their fault. They need windows to work, not work sometimes with some programs. Two bits, 1 or 0, 32 times equals 2^32. Please don't blame MS for not trying to get you more then this.
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July 9, 2010 4:36:59 AM

4745454b said:
Thats why I mentioned it. There are work arounds, but they tend to suck. Mark came in and "blasted" MS indicating its their fault that 32bit windows is limited to 4GBs of ram. Because they don't include support for some "crazy" memory scheme doesn't really make it their fault.


Microsoft write Windows. Microsoft refuse to support PAE on desktop versions of Windows. Microsoft are entirely responsible for limiting desktop versions of Windows to 4GB when they could support 64GB. I don't know who else you think could be responsible for Microsoft refusing to support a feature in a Microsoft product.... a feature which they do support in other Microsoft products.

Quote:
They need windows to work, not work sometimes with some programs. Two bits, 1 or 0, 32 times equals 2^32. Please don't blame MS for not trying to get you more then this.


PAE just works so long as your OS supports it. Microsoft support it in server versions -- you know, the versions that are expected to run 24/7/365 with minimal downtime -- but refuse to include that support in desktop versions.

Similarly, Linux servers have been using this 'works sometimes with some programs' work around for years, and they're often running critical infrastructure which is expected to be much more reliable than Windows servers. PAE is a kludge, but if you support it then it just works.
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a c 215 $ Windows 7
July 9, 2010 5:00:46 AM

@ MarkG:

Lets stop beating a dead horse here. Microsoft chose not to support PAE in their desktop operating systems. Get over it and move to a 64 bit version of Windows. You're right on the borderline of trolling with these kinds of posts. I suggest you stop.

@ the OP:

You could always buy a 64 bit version of Windows 7 Professional or higher to take full advantage of > 4GB of ram, then set up a copy of Windows XP Mode for your development needs, as Jonmor suggested.

And just for clarification on your point for anyone else reading this, the 2TB partition size limit only applies to MBR based partitions. GPT (GUID Partition table) partitions have a maximum size of 18 exabytes, and are bootable partitions, but only in EFI based computers.
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a b $ Windows 7
July 9, 2010 7:20:11 AM

You need more then just your OS to support PAE as well. The programs themselves need to support it, as do any drivers involved as well. If the program or driver doesn't support, you don't get. Which is why I said sometimes.
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July 9, 2010 8:48:40 AM

@ MarkG:
As 4745454b says drivers need to support PAE, you can actually turn it on in XP 32 but the reality was it tended to cause a large number of BSODs due to drivers assuming a 32bit addressing size, not the 36bit that PAE uses (which affectively looks like 64bit to the driver since it cannot allocate 36bits).
To be honest there is very little reason to stick with 32bit Windows unless you have a small amount of memory (<4GB) or you really need 16bit support without the use of emulation.
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a b $ Windows 7
July 9, 2010 1:21:13 PM

PAE or whatever, I'm still waiting for the OP to answer why he's DOS programming on a Core i7...
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a b $ Windows 7
July 9, 2010 1:24:23 PM

PAE.... Physical Address Extensions”.

Among other things, this allows an added table the OS can use to add the “same” address in more than one place. Think of this as adding a "street name" to your "address". 1234567890 on table A is not the same as 1234567890 on table B. The limitation is that this *must* be provided for in your programs and drivers in order to work. If your mailman only looks at the '1234567890' but never looks at the street name, then he can and will sometimes deliver a letter to the wrong place. The same thing is true of PAE - If/when then individual program haven’t been coded to look in multiple tables for the needed memory locations in addition to the numerical addresses, messages can and will sometimes go to the wrong place. In Windows, this is a “memory access violation”, and results in a blue screen. Additionally, individual programs under PAE can still only use up to 4 GB, and only *if* they are coded to take advantage of addresses above the usual 2GB worth of address space made available to apps in x86 Windows. The same applies to Drivers and the rest of it: on an x86 box, PAE or no, only a 4GB range per instance is accessible at a given time.

In short: PAE is not that great. In a server environment the number/version/type of programs and drivers can be tightly controlled, so this works. Therefore this functionality is available on server versions of 32 bit Windows (NT, 2003, 2006, and 2008***). In a consumer environment, this is not true at all. Therefore, on the desktop PAE is only available for the security related purpose of enabling DEP

Bottom line for ‘regular’ users: If you want to use 4 GB of RAM or more, then you should buy 64-bit hardware and use a 64-bit OS.

MSFT’s Page stating XP is 4GB of RAM and 4GB Only
http://www.microsoft.com/whdc/system/platform/server/PA...


***It has been announced by Microsoft that Windows Server 2008 is the last Server OS which will be available in a 32 bit version. Going forward, Server editions will all be 64 bit. There are also strong rumors that Windows 8 will similarly be 64 bit only, but this has not been confirmed.
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a b $ Windows 7
July 9, 2010 1:44:48 PM

jmichae3 said:
I am thinking of buying a new machine with windows 7. I need to do DOS development. only 32-bit OS's come with command.com which is required for doing DOS development.
I have to choose between a motherboard with a lesser processor and 4GiB dual-channel ram or a triple-channel architecture system that has 6GiB ram or more.


Depending on system configuration, anything more than about 3Gb of physical memory will be inaccessible by a 32 bit OS due to address space limitations. Since physical RAM is allocated last it has little/no impact on the performance of the rest of the system.


Quote:
1. my understanding is that the definition of 32-bit OS is that it can only access 4GiB of ram and it is MBR+BIOS based which also has a 32-bit limitation, but not limited to 2GiB disk size due to cluster sizes. My concern is the memory. is this true for 7? I currently have 32-bit XP on an old P4.


As pointed out already: Disk size is no concern in a desktop environment. The issue with your proposed configuration is related to addressable space.


Quote:
2. Has anyone ever gotten xp mode to work with an OEM windows 7 pro?


Not personally - Basically, "XP Mode" is a cheap Virtual Machine which happens to include a licence for XP SP3 and a little bit of code that allows shortcuts to exist on the normal desktop which point to apps which must run in the VM. Other vendors, including Microsoft, have better VM's. The value add for XP Mode is the included XP licence.

Quote:
3. can I use a triple-channel mb with 6GiB ram with 32-bit 7?


You may absolutely install the DIMMS on your motherboard, adn they will function. Address Space exceeding some number around 3~3.5GB will be inaccessible due to limitations of the OS.
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a b $ Windows 7
July 9, 2010 2:05:42 PM

MarkG said:


PAE just works so long as your OS supports it. Microsoft support it in server versions -- you know, the versions that are expected to run 24/7/365 with minimal downtime -- but refuse to include that support in desktop versions.



You, Sir, have been misinformed if you believe what you appear to be saying.

I will absolutely grant there is no reason why applications and drivers which are otherwise Properly Coded To Take Advantage Of Multiple Address Tables could not run in an OS which has PAE enabled for the purpose of expanding address space. And that hacking a desktop version of windows to access this functionality has little/no effect on the OS itself.

But the reality is that software written for the Desktop often is NOT properly coded for this purpose. Therefore it is a crap shoot whether something will work or not. It's also rather maddening to troubleshoot, since the Blue Screens this issue will inevitably cause will be random. This little piece of reality is why Microsoft disables PAE for the purpose of expanding address space on their Desktop operating systems. It's not a technical issue on the OS side. It's a matter of supporting the thousands and thousands of apps and devices which are already out there, and not breaking them retroactively.

And - as pointed out above - why would anyone want/need to run a kludgy workaround when it's better, easier, and supported to simply use x64 Windows? The reason I've been given time and again why people want this is "..to run my old non-Vista/Win7 compliant applications and/or devices". Well.. Let me ask you this: If they're old then they therefore only support XP/x86 conventions, such as a default 2GB address space for apps and 2GB for the system, right?? That being the case, why would anywone want to spend more money on hardware which the old stuff you have laying around the house can't even use?? To what purpose?? So you can look at My Computer and see 8GB? That's dumb. If the app or device is that important, then fine! Just build it the CHEAP environment it needs to function, or just continue to use the old box, and save the money for something else.

It's really simple: If you need to support that much hardware resource, just go 64 bit. If you need older x86/XP stuff, then why spend the money on hardware the old devices/apps can't take advantage of anyhow? Just build a $200~300 sh*tbox - (which incidentally will be orders of magnitude better/faster than the hardware anything that old was actually designed to run on) - and put the rest of the money to better use.
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July 16, 2010 8:46:43 AM

4745454b said:
I can't even begin to understand what your asking in part one. We haven't been limited to 2gb disks for quite some time. If your running a 32bit windows os your limited to 4GBs total. You should have around 3.25 available unless your running CF/SLI. Because of this I wouldn't bother with 6GBs or higher. I'm also trying to understand why your getting a huge i7 system if your just programing dos. Get a cheap older system and be done with it. As for 32bit vs 64bit can you use Dosbox or something like that?

2) Win 7 home premium doesn't officially come with XP mode, though there are hacks to make it work. All versions higher then HP come with XP mode. Whether its OEM or retail shouldn't matter. (not that I've heard anyways.)

3) You can, but see point one above. Why buy 6GBs worth if you'll only have 3.25GB to use? There is so much about this post that I don't understand.


Look guys, I don't ONLY do dos apps. I also target for win32 and x64-bit apps, and also for the web, among other things.
gimme a break - I'm a developer. I write in lots of languages for lots of targets.

So I need a system that is going to make it easiest

the thing that hurts me is the tradeoff between having more memory in 64-bit OS, which I really want, and the ease with which I can do DOS development for making bootable cd applications and also for making the bootable FreeDOS OEM ISO and some other utilities.

but due to xp mode being stuck in another filesystem (is it?), I am going to choose to stick with 32-bit.

I also do video work and a lot of compression and multitasking and multithreading, so as many cores as I can get, the better.

why 6GB? because that's the minimum RAM configuration for maximum speed in DDR3 1333. I don't mind sacrificing some memory just to get the speed. and who knows? maybe I'll go to 64-bit windows 8 someday.

don't dis me and make a bunch of posts because I didn't explain every little detail about development.

I know that what's left of the 4GB is taken up by (possibly) memory mapping of PCI ports and vga memory, which in my case should be about 512MB.
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July 16, 2010 8:55:18 AM

LePhuronn said:
PAE or whatever, I'm still waiting for the OP to answer why he's DOS programming on a Core i7...


how many compiles can you execute at the same time as other programs? multitasking. my computer is a workhorse. I typically have about 30+ applications running on the computer at once, most of which are cmd shells, and sometimes those cmd shells call command.com.
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July 16, 2010 9:01:15 AM

Best answer selected by jmichae3.
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a b $ Windows 7
July 16, 2010 9:03:38 AM

If I can add a quick two-cents worth, I would choose 64-bit Windows 7 and then run a 32-bit version of Windows in a VM (XP Mode or some other of your choice). Access to the host file system from the VM is no problem. Most provide some sort of system for sharing folders but if not you can just share the drive or folder and access it over the network from the VM.

The advantages of 64-bit Window, particularly if you are going to use more than 4GB of memory (remember that in practice you don't even get all that 4GB with a 32-bit system) far outweight the slight inconvenience of doing things this way for the odd DOS compile. With 30+ applications running at once you could really do with more than the 2.5-3GB of RAM that 32-bit Windows can access.
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a c 209 $ Windows 7
July 16, 2010 5:20:27 PM

jmichae3 said:
but due to xp mode being stuck in another filesystem (is it?), I am going to choose to stick with 32-bit.
XP mode runs of virtual hard drives on the host system, but it can also access host system folders using file shares. Once you set this up inside the XP system it's pretty transparent and you should be able to share files between the systems without any particular problems.
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