Maximum amount of memory on a 486

Discussion about old PC hardware.

Re: Maximum amount of memory on a 486

Postby Scali » 2017-12-01 @ 14:50

I'll have to check my Compaq Deskpro XL466.
It's a very late 486, with PCI and 72-pin DIMMs and all. It's also very high-end (workstation-class), with onboard LAN and SCSI.
I wonder how much memory that one could take.
Here's a Russian page on it with good pictures: http://ru.pc-history.com/compaq-deskpro-xl-466.html
Note that the CPU, chipset and memory are on a special expansion board.
I have a Deskrpo XL6200 as well, which is a Pentium Pro 200. It's basically the exact same machine, apart from that CPU board. I even tried swapping the CPU boards between the machines, and that worked fine.

Edit: According to this, it's only a measly 128 MB for the 486: https://support.hp.com/hr-en/document/c00355459#AbT0
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Re: Maximum amount of memory on a 486

Postby clueless1 » 2017-12-01 @ 14:59

FFXIhealer wrote:I wouldn't know. I've personally never had to use an IDE or SATA riser card via PCI or ISA. All of my computers always had IDE or SATA controllers built into the motherboard.

But on my Windows 98SE system, I did to a Crystal Disk test and I think the board supports ATA/33, but I'm only pulling around 25MB/s read speeds (19.5MB/s write) on my Western Digital Caviar 40GB hard disk drive... for what it's worth. I guess that means the HDD is being limited by the interface. The 3TB Seagate drive running on my 2016 gaming rig is pushing 170MB/s sequential read and 175MB/s write speeds (SATA III, or 6Gbps). And my 850 EVO is pushing 557MB/s read and 534MB/s write on the same bus.

Depending on which model, RPM and platter size, your 40GB Caviar may be naturally maxing out at 25MB/s. The only way to know for sure is to test it on a more modern system on at least an ATA66 interface. I do know the 20GB/platter 7200RPM WD400BB from circa 2000 topped out at a little less than 34MB/sec.
The more I learn, the more I realize how much I don't know.
Let's benchmark our systems with cache disabled
DOS PCI Graphics Card Benchmarks
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Re: Maximum amount of memory on a 486

Postby BitWrangler » 2017-12-01 @ 15:02

Yah, that's about right for a 2MB cache one, a year or two later the 8MB ones would do 50-60MB sustained on ATA-66 or better.
Basement full of ancient PC stuff, starting to go through it. Most recently toyed with DOS era stuff 15 years ago, so memory might be rusty. So what's this BitWrangler guy's deal ??? >>> http://www.vogons.org/viewtopic.php?f=25&t=56382
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Re: Maximum amount of memory on a 486

Postby gdjacobs » 2017-12-01 @ 16:50

Gotta love those WD JB drives.
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Re: Maximum amount of memory on a 486

Postby kazblox » 2017-12-01 @ 16:59

A 486 can address a maximum of 4GB physical memory. Good luck trying to find a chipset and a BIOS that lets you do that though, even if you have the technology to directly solder and wire a ton of sticks.
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Re: Maximum amount of memory on a 486

Postby CkRtech » 2017-12-01 @ 20:26

I suppose looking into late, specific server/workstation 486 models is the way to go. The more this topic gets bumped, the more interested I am in this trivia question.
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Re: Maximum amount of memory on a 486

Postby mrau » 2017-12-01 @ 20:36

https://en.wikipedia.org/wiki/Sequent_Computer_Systems
384 mb ram here, but thats low end; i'm pretty sure i've seen bigger and meaner years ago..
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Re: Maximum amount of memory on a 486

Postby FFXIhealer » 2017-12-02 @ 05:38

clueless1 wrote:
FFXIhealer wrote:I wouldn't know. I've personally never had to use an IDE or SATA riser card via PCI or ISA. All of my computers always had IDE or SATA controllers built into the motherboard.

But on my Windows 98SE system, I did to a Crystal Disk test and I think the board supports ATA/33, but I'm only pulling around 25MB/s read speeds (19.5MB/s write) on my Western Digital Caviar 40GB hard disk drive... for what it's worth. I guess that means the HDD is being limited by the interface. The 3TB Seagate drive running on my 2016 gaming rig is pushing 170MB/s sequential read and 175MB/s write speeds (SATA III, or 6Gbps). And my 850 EVO is pushing 557MB/s read and 534MB/s write on the same bus.

Depending on which model, RPM and platter size, your 40GB Caviar may be naturally maxing out at 25MB/s. The only way to know for sure is to test it on a more modern system on at least an ATA66 interface. I do know the 20GB/platter 7200RPM WD400BB from circa 2000 topped out at a little less than 34MB/sec.


This is my drive. I have two of them.
https://www.cnet.com/products/wd-caviar ... ies/specs/

Short story, it's ATA-100 interface should allow nearly 50MB/s sequential read speed. And the drive spins at 7,200 RPMs, which is great for games. Playing Turok and Turok 2, I never noticed level loading. It's not until much bigger games that I saw that, like Return to Castle Wolfenstein.
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