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Thread: Fastest 486 Disk I/O

  1. #1

    Default Fastest 486 Disk I/O

    I have been trying to optimise my old 486 VLB systems for disk performance, and I find this to be the most challenging aspects of the PC to improve on.

    The VL Bus is capable of something between 32MB - 132MB/sec (depending on the configuration). The fastest VLB controllers I know of are EIDE PIO Mode4. I have some that claim to be "PIO5" using DMA, but I haven't gotten that working yet. I have three controllers. A Promise, a QDI and a DTC. PIO4 is supposed to do 16MB/sec. However, I am not able to get performance anywhere near this using modern 7200 EIDE drives that I know are capable of very high transfer rates. The best I can do for average transfer rates is about 7MB/sec. Peak is maybe around 11MB/sec. I have heard of people claiming 11MB/sec average transfer rates on VLB, but I really wonder how they do this. As you know, configuring the VLB controllers can be challenging. There are many settings in the BIOS, DOS and Windows drivers to take into consideration. I am wondering if anyone has a good procedure for squeezing out as much as they can from their VLB controllers.

  2. #2
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    You need to define the benchmark (what software and what test).

    Are you benchmarking in Windows (which version) or DOS?

    I would think the fastest drive connected to a caching VLB card (the onboard processor will take the load off of the 486 CPU just like DMA mode would on faster chips) would be the fastest controller.

    Currently I have a promise 4030vl+ with 16MB of ram running in a 486 I could benchmark.

  3. #3

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    One word: SCSI

    A good VLB SCSI controller with a good drive is going to beat the daylights out of an EIDE controller. SCSI drives generally have more cache on them, and the ability to queue commands and optimize the motion of the heads helps real world performance.

    Under realistic conditions it does not matter much. The drives of the era are far slower than what the bus can handle. Perhaps a new drive can burst data to the controller really quickly if the data is in the cache first, but for normal operation that is the exception, not the rule.

    To test the throughput of the controller (and not the drive) get a test program that does sequential reads, or better yet, just keeps reading the same sector over and over again. It has nothing to do with reality, but it will tell you what the controller/bus is capable of.

    My favorite VLB SCSI controller is the Buslogic BT-445s. Buslogic was bought by Mylex, and after that I lost track of them. Great hardware with great OS support at the time - Novell, DOS, OS2, Windows, Linux, etc.

  4. #4
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    Quote Originally Posted by mbbrutman View Post
    One word: SCSI

    A good VLB SCSI controller with a good drive is going to beat the daylights out of an EIDE controller. SCSI drives generally have more cache on them, and the ability to queue commands and optimize the motion of the heads helps real world performance.

    Under realistic conditions it does not matter much. The drives of the era are far slower than what the bus can handle. Perhaps a new drive can burst data to the controller really quickly if the data is in the cache first, but for normal operation that is the exception, not the rule.

    To test the throughput of the controller (and not the drive) get a test program that does sequential reads, or better yet, just keeps reading the same sector over and over again. It has nothing to do with reality, but it will tell you what the controller/bus is capable of.

    My favorite VLB SCSI controller is the Buslogic BT-445s. Buslogic was bought by Mylex, and after that I lost track of them. Great hardware with great OS support at the time - Novell, DOS, OS2, Windows, Linux, etc.

    One word: 'RAID-0'. Just make sure you have a backup strategy... Buslogic made some nice SCSI controllers back in the day. They never seemed to be the fastest or most feature laden, but I never had compatability problems with them, either...

    -Scrappy

  5. #5

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    I've been doing my benchmarks under windows, because I find it much harder to get the 32-bit disk access going when in DOS. I have been using Wintune 2.0 which I realise isn't exactly the best test to run for disk performance.

    I'll have to look into these Bustek/Bus Logic controllers. I did some reading, and people seem to say pretty good things about them. Though, I am kind of scared to use VLB SCSI after dealing with Adaptec VLB SCSI boards. Do you really think going SCSI on the VLB would make a big difference though? From what I understand VLB can't really do DMA. It seems going with a caching VLB controller would provide some interesting results, at least it should relieve the CPU of some load. That AMI FaskDisk VLB SCSI caching controller that UnknownK picked up the other day is probably the way to go. Too bad I didn't bid on it while I had the chance :P

    I'll probably just stick with my EIDE controller until another FastDisk pops up. Now when I think about it, perhaps my disk scores aren't really so terrible...and just for the record, I am using an IBM 34GXP ATA disk drive on my VLB EIDE controller. It's a 7200RPM drive with a 2MB buffer.

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