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486DX-50 MHz EISA system

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Reply 40 of 44, by mpe

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weedeewee wrote on 2021-04-23, 12:05:

EISA has a 32 bit data bus so would be four times as fast as an equivalently clocked 8 bit ISA bus or twice as fast an equivalently clocked 16 bit isa bus.
and it has a 32 bit address bus.

Yes, in theory. The bus might be twice as fast if using 32bit writes to video RAM which is not common in DOS and not even in Windows 3.1.

EISA graphic card market pretty much concluded in 1992 or so, whereas ISA cards continued to be produced for a couple of extra years so you can get slightly better cards for ISA.

Even the ELSA Winner 1000 that has both EISA and ISA connector showed a hair better performance in ISA mode for some reason.

EISA was made for SCSI, network cards and such. The main benefit was CPU-freeing bus-master capabilities and arbitration and not the bandwith.

Blog|NexGen 586|S4

Reply 41 of 44, by evasive

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So a Genoa board sold under the FreeTech brand since the POST screen mentions the "10X".,or the other way around as the markings absolutely say: FreeTech board (ASY xxx-00ABC-xx is FreeTech/Flexus by definition). This BTW means the model name is 486F10X, so thank you for that info, still we would like to have a bios dump 😁 One reason for that is to find the actual core version of the bios, as the POST ID seems to be mutilated a bit. Where that 1017 is, the should be 101094-<chipset info>-8/0/K something I think. The only way to dig that up is from the bios dump itself.

Reply 42 of 44, by simon_e_hall

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evasive wrote on 2021-04-24, 10:55:

So a Genoa board sold under the FreeTech brand since the POST screen mentions the "10X".,or the other way around as the markings absolutely say: FreeTech board (ASY xxx-00ABC-xx is FreeTech/Flexus by definition). This BTW means the model name is 486F10X, so thank you for that info, still we would like to have a bios dump 😁 One reason for that is to find the actual core version of the bios, as the POST ID seems to be mutilated a bit. Where that 1017 is, the should be 101094-<chipset info>-8/0/K something I think. The only way to dig that up is from the bios dump itself.

Was playing around with the machine today, seeing if there was any ways I could tweak the BIOS (Wait states, timings, etc) or put a different BIOS on the board.

I have attached a zip file with a few different saves of the BIOS using NSSI and AMI BCP, also a couple of screen shots for further information. I would be interested to see someone else's analysis of this BIOS, this board is a bit of a mystery, only found one press cutting for it online, which again states it is a Freetech board.

The lack of BIOS options is annoying, especially when compared with other BIOS options of the era, I was thinking of making my own BIOS image, but it has been a very long time since I did that. (i.e. do a hash of two similar BIOS images one with EISA compatibility and another with more flexibility).

So I tried a little experiment, I inserted a similar AMI 486 ISA BIOS (had a few lying around) in the machine to see what would happen, better then expected really:

1) The ISA BIOS only sees up to 32MB

2) Does not initialise the EISA cards, apart from the VGA which works from boot

Both results as expected, but it would successfully boot up to needing me to insert a boot disk, I was just seeing if playing with any wait states on a BIOS with more options would improve memory performance, but this all needs a little more experimentation, i.e. put a ISA IDE card in and see if that works and boots, etc. But now my baby son is awake, so no more playing with computers for me today.

Also I put 15ns cache chips in, as I said before from experience this usually achieves nothing apart from bragging rights but you never know, and sure enough, it achieved nothing, benchmark results remained the same.

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  • BIOS ID Analysis.jpg
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  • 486 EISA BIOS Chip.jpg
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Reply 43 of 44, by weedeewee

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simon_e_hall wrote on 2021-04-26, 12:27:

So I tried a little experiment, I inserted a similar AMI 486 ISA BIOS (had a few lying around) in the machine to see what would happen, better then expected really:

If the original bios is an ami bios one, you could try a little experiment with an old Amisetup util which allowed to change hidden settings

Reply 44 of 44, by simon_e_hall

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weedeewee wrote on 2021-04-26, 13:59:
simon_e_hall wrote on 2021-04-26, 12:27:

So I tried a little experiment, I inserted a similar AMI 486 ISA BIOS (had a few lying around) in the machine to see what would happen, better then expected really:

If the original bios is an ami bios one, you could try a little experiment with an old Amisetup util which allowed to change hidden settings

Tried that to begin with, interesting to note how many options are hidden, strange things like turning the memory tick sound off, most of the deleted options are shadow locations, which I had a play with but again not much joy.

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  • AMISETUP001.jpg
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