I was wondering if there ever was an upgrade path for (486 Socket - pre Socket 1) 486DX-50 CPU.
My board is ISA/EISA with fixed 50 MHz crystal (and 14.3 MHz for EISA). So no issues with VLB. Is there any clock doubling chip that can handle the 50 MHz FSB?
I can use a voltage interposer if needed. Could Am5x86 p75 run at 3x50?
The DX-50 is one of the worst CPU's for upgrading. There is no upgrade path available for Intel Overdrive replacements.
wrote:I can use a voltage interposer if needed. Could Am5x86 p75 run at 3x50?
Yes, the Am5x86-P75+ can handle 50 MHz FSB but not at 5V. Keep in mind: it requires a Socket 3.
If there was no 5V limit you can run a DX4 at 2x multiplier with 50MHz FSB very nicely.
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Thanks. I actually just tried it and got the Am5x86 p75 working. Clearly, it doesn't need Socket 3. It just needs 3.5V 😀
It is slow like hell though at 150 MHz it is only 1.4x faster than 50 MHz. At pure ALU tests it is better but still slower than ordinary VLB-era 486 chipset.
I think slow cache/mem and ISA card is holding it back. Will see if an EISA VGA will be any better...
wrote:Thanks. I actually just tried it and got the Am5x86 p75 working. Clearly, it doesn't need Socket 3. It just needs 3.5V :) […]
Thanks. I actually just tried it and got the Am5x86 p75 working. Clearly, it doesn't need Socket 3. It just needs 3.5V 😀
It is slow like hell though at 150 MHz it is only 1.4x faster than 50 MHz. At pure ALU tests it is better but still slower than ordinary VLB-era 486 chipset.
I think slow cache/mem and ISA card is holding it back. Will see if an EISA VGA will be any better...
I'm surprised, with both running at 50 MHz external, I'd suspect the 150 MHz having a clear lead ..
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I'd think too. However, Slow S3 801 ISA VGA, 25ns L2 cache, untuned config (no CMOS due to dead Dallas) and no ECU...
I will need to work a bit on this one to see if I can squeeze a bit of extra power.
5x86 at 150 should be pretty fast, even on an old system. I've tried this upgrade on my old 5V boards.
In addition to the am5x86 and the DX4, the Cyrix 5x86 is another chip that could possibly work on your board at 2x50.
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V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium
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I just picked one of these up from Poland for about $15. Has a DX2/66 chip in it for some reason, but it'll do ( I think, I looked at it briefly as I also got a 286 and a 486 in the same shipment) 2, 2.5x and 3x at 3.3 or 3.45 volts. I wonder if I can upgrade my Siemens DX2/66... to a 133 MHz 5x86!
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wrote:Thanks. I actually just tried it and got the Am5x86 p75 working. Clearly, it doesn't need Socket 3. It just needs 3.5V 😀
It is slow like hell though at 150 MHz it is only 1.4x faster than 50 MHz. At pure ALU tests it is better but still slower than ordinary VLB-era 486 chipset.
I think slow cache/mem and ISA card is holding it back. Will see if an EISA VGA will be any better...
Which benchmark are you using? If it's graphical, yes, ISA will be a huge bottleneck. EISA will be better when it comes to bandwidth, but chipsets are also ancient compared to VLB/PCI.
If it's not graphical, something on that board needs tuning. Does it support WB cache? And how are the wait states?
I've not done a comparative benchmark of 486 chipsets, but I did do that for So5/7 once. Mem performance differed more than a factor 2 between the fastest (Aladdin IV just beat i430TX) and slowest (UMC 890C), clock for clock with same CPU and RAM. Wouldn't surprise me if differences are just as big with 486.
