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8bitbubsy
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Joined: 28 Sep 2011
Posts: 40
Location: Norway
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 Posted: Sun Feb 12, 2012 11:26 pm Post subject: |
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| DonutKing wrote: | Hello
I am also looking for this file  I am trying to restore an old 486 with an IH4077 motherboard, I am trying to make it work with a DX4 Overdrive but it won't boot. I'm hoping the new BIOS fixes this issue but I am unable to locate the file anywhere on the internet...
Would someone be kind enough to provide me with he BIOS update file?
Thanks very much |
http://16-bits.org/etc/ih4077d.208G
Here you go. Keep in mind that this motherboard does not support BIOS flashing internally, so you need a 27C512 (64kB/512KBits) EE/EPROM with the BIOS flashed onto it. I've done this, and it works fine.
As for the machine not booting, check the jumpers. Jumper settings are here:
http://stason.org/TULARC/pc/motherboards/M/MITAC-INTERNATIONAL-CORPORATION-486-IH4077D.html
Make sure that JP36 is set to 1-2 (33MHz bus, the CPU has an internal clock multiplier), also make sure that the CPU settings are set to DX2/DX4 (they share the same jumper setting), and that you change the clock multiplier settings on the motherboard as well (prolly 3x (33MHz x 3 = ~100MHz)).
If the CPU requires 3.3v, you need to do a kind of tricky voltage regulator mod. There's a connector next to the CPU with the text "VCC, GND, VCC3, VCC, GND, VCC3". Basically you unplug the big whiter jumper that is in there, and you line up both the VCC and both GND to a 3.3v reg, then you take the 3.3v out and line it up to the two VCC3 lines.
To get 5v mode again, remove your mod and reinsert the white jumper block (or short both VCC with both VCC3. GND can stay open).
The motherboard is sporting a Socket 3 CPU socket, which means that it has the auto-sensing pin for 5v/3.3v selection, but I did a check on this and the motherboard doesn't supply 3.3v, so inserting a DX4 that is 3.3v will result in a 1.7v too much and a PC that freezes after just seconds.
If the system still refuses to boot, bear in mind that this motherboard is kind of picky about RAM sticks, so try other ones. I've had best luck with single-sided RAM sticks.
Also make sure the PSU delivers clean voltage lines within good range. 5v +- 3%, 12v +- 10%, -12v +- 10%.
Hope this helps! |
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DonutKing
Pilgrim
Joined: 12 Feb 2012
Posts: 3
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| Posted: Mon Feb 13, 2012 1:09 pm Post subject: |
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Thanks very much!
Are you the same 8bitbubsy from EAB?
I have an EPROM eraser and programmer so flashing it isn't a problem.
I've confirmed the jumpers are correct, and I'm using a DX4 Overdrive which has a 3.3V regulator onboard.
It works perfectly with a DX2-66, and even an AMD 100MHz DX4 (a 3.3V processor but I have a few spare so I wasn't worried about toasting it) but it fails with the Intel DX4 overdrive and a Pentium Overdrive. The AMD chip has only 8kb internal cache which the Intel DX4 and POD both have 16kb so I suspect that's part of the problem. I'm hoping the BIOS update will resolve this
Yes funnily enough the 3.3V AMD processor was quite happy running at 5V, I had it running like that for several hours (with a decent size heatsink/fan) with no signs of instability... I've heard that some of these AMD chips are 5V tolerant but I don't think the particular one I have is, it says 3.3V on the top and I never found a definitive list of the 5V tolerant AMD CPU's...
Again thanks very much for the file
Last edited by DonutKing on Mon Feb 13, 2012 1:14 pm; edited 1 time in total |
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8bitbubsy
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Joined: 28 Sep 2011
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Location: Norway
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| Posted: Mon Feb 13, 2012 1:12 pm Post subject: |
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Yep, I'm the Amiga 8bitbubsy.
EDIT: Yes, the 3.3v CPUs can run at 5v if you have good cooling, but it will significally shorten its life span, also you *will* get some funky behaviors at times. I ran it for hours too, but it got extremely hot (I ran it because I thought the mobo auto-sensed it and switched to 3.3v).
Intel DX4 100MHz is supported even on the old '94 BIOS, it's not the reason it won't boot.
If I were you, I'd check for any +3.3v lines from the PSU and hook that up to the two VCC3 lines near the CPU power jumper/socket, and let GND/GND/VCC/VCC stay open. This way you can run the normal DX4 CPUs fully stable with just a heatsink, 24/7.
If you still use the old PSU it probably doesn't have any +3.3v lines... Only solution then is to do the volt reg mod or mod a modern ATX PSU to work with it. Just cut the wires from the motherboard power connectors and solder new ones from the new PSU, making sure you have the right lines. Oh, and for the power button you just connect the PWR_ON motherboard PSU wire and a GND wire to the switch.
I did this hack, since the old PSU I had was old and probably about to get funky. |
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DonutKing
Pilgrim
Joined: 12 Feb 2012
Posts: 3
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| Posted: Mon Feb 13, 2012 1:20 pm Post subject: |
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I'm using an AT PSU so it won't have 3.3V. Strange that the DX4 Overdrive doesn't work with it. I know the CPU is good because it works in another board.
I'll have a fiddle with it later tonight and see how it goes. |
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8bitbubsy
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Joined: 28 Sep 2011
Posts: 40
Location: Norway
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| Posted: Mon Feb 13, 2012 1:26 pm Post subject: |
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| DonutKing wrote: | I'm using an AT PSU so it won't have 3.3V. Strange that the DX4 Overdrive doesn't work with it. I know the CPU is good because it works in another board.
I'll have a fiddle with it later tonight and see how it goes. |
Okay, I see.
Just some other helpful tips for this motherboard:
Make sure you have the correct motherboard cache jumper settings.
I have 256kB cache in mine, so it's naturally set to 256kB. Look at the cache chips to see what size they are in terms of bits, and do the kilobits->kilobytes calculation yourself. Correct cache setting = important.
There's a jumper for "local bus waitstate" too, JP37. Set it to 0 waitstates (1-2 jumper pos) for a boost in VESA speed, since the motherboard bus runs at 33MHz with the DX2/DX4.
If you were to run a DX 50MHz (no internal clock multiplier), the VESA graphics card would *probably* struggle at 50MHz unless it's a very fast VESA card. So 1 waitstate would be essential there.
Also as said, make sure JP36 is set to 1-2 as well (33MHz).
For DX4:
JP22 should be open.
JP26, JP30, JP31, JP32 should be closed.
EDIT:
I just come to remember something...
The later revisions of DX2 and DX4 had a "write-back" cache settings, which is faster than write-through. If you know that your CPU supports this (check wikipedia for more information), set the CPU write-back cache to enabled in the BIOS. If not, make absolutely sure it's set to write-through. (This setting is only in the newest BIOS I linked to).
Gotta have everything at their optimal settings for a nice speed boost.  |
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Karlsweldt
Mobo-fu Master
Joined: 12 Nov 2003
Posts: 19020
Location: 07438
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| Posted: Tue Feb 14, 2012 8:43 am Post subject: |
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Check the FSB settings for base speed. The DX2-66 uses a base 33 mHz bus. The DX2-50 and DX4-100 use a 25 mHz base. If the FSB is too fast, then the CPU will become very unstable.
The Pentium Overdrive CPU may be a 5 volt core.. check the label. At 3.3 volts, it will not clock properly. Here is a link to basic specs for the Pentium OD CPU class.. http://www.cpu-world.com/CPUs/Pentium/TYPE-Pentium%20overdrive.html
The older Socket 3 mobos may not have the jumper settings or regulators to handle newer CPU types. If you still have the setup manual, check same. Some mobo models from 1994 did have a Socket 4 and a large field of jumpers to set. (As with the Opti 895 "Green" model.)
Older CPU types may have had a L1 cache on-die, but the L2 cache was on the mobo. If on the mobo, its speed may not be up to higher FSB ratings.
For a listing of most CPU socket types, here is a link.. http://www.hardwaresecrets.com/article/373
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8bitbubsy
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Location: Norway
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| Posted: Tue Feb 14, 2012 9:46 am Post subject: |
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| Karlsweldt wrote: | Check the FSB settings for base speed. The DX2-66 uses a base 33 mHz bus. The DX2-50 and DX4-100 use a 25 mHz base. If the FSB is too fast, then the CPU will become very unstable.
The Pentium Overdrive CPU may be a 5 volt core.. check the label. At 3.3 volts, it will not clock properly. Here is a link to basic specs for the Pentium OD CPU class.. http://www.cpu-world.com/CPUs/Pentium/TYPE-Pentium%20overdrive.html
The older Socket 3 mobos may not have the jumper settings or regulators to handle newer CPU types. If you still have the setup manual, check same. Some mobo models from 1994 did have a Socket 4 and a large field of jumpers to set. (As with the Opti 895 "Green" model.)
Older CPU types may have had a L1 cache on-die, but the L2 cache was on the mobo. If on the mobo, its speed may not be up to higher FSB ratings.
For a listing of most CPU socket types, here is a link.. http://www.hardwaresecrets.com/article/373 |
DX4-100 has a 2x-3x internal clock multiplier, so the motherboard bus needs to run at either 33MHz or 50MHz (not 25MHz). 
Only certain DX4 models can take a 50MHz input clock, most of them rely on 33MHz only.
DX4-75 on the other hand, takes a 25MHz input clock.
The name DX4 is misleading; It's triple-clocked (or doubled) internally, not quad-clocked. |
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Karlsweldt
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Joined: 12 Nov 2003
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Location: 07438
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| Posted: Wed Feb 15, 2012 8:25 am Post subject: |
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Sorry I was not more precise. SOME of the early DX4 processors did require a 25 MHz bus. Others required a 33 MHz or 50 MHz bus.
I have worked on computers since the early 1980s, and back then all you had were 286/386/486 CPU types. And maybe the "Pentium Overdrive", a new version that gave higher processing speed with little or no modification to the motherboard. Motherboards were expensive back then.. with mostly separate dedicated chipsets, no LSI (Large-Scale Integration) as today's motherboard models. This link from Intel describes the 486 class of processor in the DX2/DX4 class.
And back then, you had the Cyrix CPU models that were based on the 386 socket design, yet equaled a 486 in performance. And even AMD had its "5x133" CPU design, which fit the Socket 7+ class.. and equaled a Pentium 90 in most operations. But that would not work in earlier motherboards with less than the Socket 7 designs.
Be thankful that the IBM design of the MCA (Micro Channel Architecture) lost out to the ISA and EISA bus standards!
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8bitbubsy
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| Posted: Wed Feb 15, 2012 10:49 am Post subject: |
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| Karlsweldt wrote: |
I have worked on computers since the early 1980s
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Heh, you could be my father. Kind of funny, I was like 2-3 years old when the DX2-66 was introduced.
The main reason I'm into old computers is because I grew up with a 486 with DOS 6.22 and Sound Blaster 16. I even edited config.sys and autoexec.bat at an age of 7-8, hoping to get enough conventional RAM to run real mode DOS games.
That hard drive was filled with *cough* cracked *cough* games. 
Anyways, the DX4-75 are the ones taking a 25MHz input clock. You said DX4-100, that's why I corrected you.
I'd love to get one of those later DX4-100 taking a 50MHz input clock, for a boost in RAM speed and VESA speed (versus 33MHz). |
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Karlsweldt
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Joined: 12 Nov 2003
Posts: 19020
Location: 07438
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| Posted: Thu Feb 16, 2012 11:29 am Post subject: |
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| Quote: | | Heh, you could be my father. |
Maybe more of a 'grandfather' type. Recently notched my life's mile-stone a 72nd time!
A lot of those processors of years gone by are no longer remembered.. or found. Salvaged for the gold content.
Today, AMD and Intel are the primary source of CPU types. But go back maybe 25 years, you had a wide field of manufacturers for CPU types. This included Motorola, NEC, Via, Cyrix and such forgotten names. Way back in 1971, a "fast" processor ran at around 400 MHz!!!!!!!!!!! And system memory may have been only around 256 KB. When the ancient XT system was popular, the 8088 CPU was top dog, running at around 4.7 MHz. But NEC developed a CPU that ran at 15 MHz and was a "drop-in" type.. the NEC V20. Ah, such blazing fast speed!!! Yet we still relied on floppy drives for all programming and file storage. A hard drive was a luxury unaffordable by most. If you had a 10 meg hard drive, you were very well-to-do!! As to DOS versions, there was constant upgrading as the processor speed and peripherals improved. Mr. Gates is well known to be the "father" of OS programming. But he once worked for IBM®, and suggested a better way to create an operating system for computers.. that got him fired! He went on to create the Microsoft® empire. But in the early years, there was a warning on IBM® manufactured computers that forbid any Microsoft® software from being installed!!
Sorry if I am an 'old fogey'. 
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