Solved Ram Drive and Hard Disk performance?

Ibm Os/2 warp 4.0 single license pack
August 13, 2014 at 08:20:38
Specs: Windows, P200+256Mb
I was wondering if anyone knows why this situation is occuring when I set up a large RAM drive. I have 256 MB of physical memory. I have set up a ram drive of 32Mb. When I use a benchmark program, the RAM test and the Hard Drive meet or excel the manufacturer specifications. I get a hard drive transfer rate of about 40MBps (Manufacturer spec is 33MBps). The SDRAM also shows high transfer too.

However, if I make the RAM Drive any larger than 32768KB (32MB), even by a single KB, the benchmarks drop to around 20-24 MBps for the Hard Disk and the RAM speed drops noticeably as well. Is there some wall that you are forced to lose performance by increasing a RAM drive beyond 32MB? Or could it be the RAM disk driver causing the problem? I use XMSDSK (Frank Uberto) which is touted as the best one you can use, which claims no 32MB limit, yet there seems to be a performance limit anyway. What's going on? I would like to use at least 128MB for a ram drive, because Win 3.11 can run just great on as low as 64MB, but getting stiffed on performance or putting excessive pressure on the hardware to do so is not in my interest either.

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August 13, 2014 at 20:01:27
✔ Best Answer

Note under "MS DOS Ramdrive":

"The MS DOS Ramdrive is limited to a maximum size of 32mb. So even if you have a lot of memory, you can't make a large Ramdrive. "

While the one you're using has no limits, there may still be a disadvantage within DOS beyond 32MB that drops your throughput...

"Channeling the spirit of jboy..."

message edited by T-R-A

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August 14, 2014 at 01:22:54
Yeah, I have been searching for more info on this issue and yes the 32Mb limit is there for a reason. But also there seems to be an issue with the chipset as well. I have an i430tx chipset that allows for 256Mb of SDRAM, but can only cache 64 Mb at a time. By using a third party ramdisk driver that breaks that barrier, the system recognizes it as new physical drive, but it's now not allocated by the memory controller and uncached - even by going over by just 1kb. So this probably explains the drop in performance. I would also suspect that a large program that does a lot of reading and writing running in the larger-than-32mb ramdrive may not run correctly as well. Which turned out to be true when I used the Arachne browser in that "illegal" environment - the program runs, but doesn't run correctly and 'misses' and often crashes. However, it runs perfectly well, such as it does with it's own bugs, if I stay at or below that 32MB limit. So this explains the drop in physical disk performance as well.

What I am wondering if there is way using software to force virtually a larger cache size out of the chipset limitation of 64mb? I don't know. Seems a shame to have all that 256mb RAM just wasted because it can't cache it all at once.

Also, there's something wrong with my own memory because I obviously discussed this very thing 4 years ago:

right here

I must be getting old.

message edited by MisterGopher

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August 14, 2014 at 16:28:03
"...there's something wrong with my own memory because I obviously discussed this very thing 4 years ago..."

"I must be getting old."

Don't worry, it's painless (mostly)....

"Channeling the spirit of jboy..."

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Related Solutions

September 13, 2014 at 12:10:34
I thought MS DOS Ramdrive was limited to a maximum size of 36mb. :)

Some cpu/board setups can only cache a limited amount of ram. :(

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September 17, 2014 at 13:03:11
I think 64MB RAM could be a limitation of Windows itself, not just the chipset. Microsoft states the virtual memory stays at 256MB once you hit 64MB RAM. That may or may not negatively large RAM applications like Photoshop 3.0.5 on Windows 3.1.

Windows 3.1 Memory Limits

I have always thought that Windows 3.1 with < 64MB RAM is a waste. I should also point out that I have never exhausted that much RAM in Win 3.1, that is a huge amount for that OS. It's not like you need an antivirus for 16-bit Windows these days.

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