MB457 V1.1 (or MB45XC v1.0???)

[Rainbow]

I have this weird board

There's "MB457 V1.1" printed on it, BIOS displays MB45XC V1.0, but I can't find any info (except that it has Y2K-buggy BIOS, which I already noticed ).
BIOS ID does not say anything: 12/20/94-UMC-498GP-2C4X6000-00
When I bought it, all jumpers were removed, so I used trial-and error method to get it working... The RTC seemed dead (everything worked except the hardware clock which was simply stopped) - I found that two pins of the chipset are bent and touching each other - I straightened them and it works now That's why the board was thrown out and sold as junk.
The BIOS is not flashable, so if I want to fix that Y2K bug, I need to have an EPROM programmed somewhere. I would like to have at least the jumper settings...

[edwin]

Mentioned here:
http://www.yiik.com/docs/awardbug_yiik.html

email them and try to get documentation
info@yiik.com


If you get it, I'd love to have a copy, this might be another board OEMd by ADI, I have a page on them and I'm still missing an ISA-only board.
http://www.plasma-online.de/english/ide ... b_adi.html

There is a newer bios for that ADI board:
2C4X6000-00: ??? / BIOS date: 07/11/95 / IO-controller: UMC-498GP / F4DXL-UC4

but haven't found it yet.

[Rainbow]

Thanks - I sent an e-mail there.
I overclocked the CPU to 40MHz, put 8MB EDO and 4x256KB SIMMs there (9MB RAM total) and let DOOM demo running for about a hour - without any problems. But Windows 95 is very unstable. Runs for a while (maybe minute or two) and then shows either BSOD (FATAL EXCEPTION 07 AT FCB2:00002FF7 - always the same addres) or Windows Protection Error (and then It's safe to turn off your computer ). I tried to run the CPU at default 33MHz and even underclocked to 25MHz and set all BIOS settings to slowest - still the same result. I think that maybe the jumpers are not set correctly or I need another BIOS.

[edwin]

07: Coprocessor Not Available Fault
This error occurs if the computer does not have a math coprocessor and the EM bit of register CR0 is set indicating that Numeric Data Processor emulation is being used. Each time a floating point operation is executed, an interrupt 07 occurs.

This error also occurs when a math coprocessor is used and a task switch is executed. Interrupt 07 tells the processor that the current state of the coprocessor needs to be saved so that it can be used by another task.

Jumper setting problem indeed.

[Rainbow]

Got no reply
I reinstalled Windows 95 and no more exceptions Seems that Windows thought that there's a coprocessor installed (it was old installation - tested with more boards, but all at least 486DX). There are some stability issues (crashing MSIE), but I hope that I will fix them by playing with BIOS settings...
I can at least do some micro-manual - what jumpers must be set for the board to work and how to configure CPU frequency.

P.S. Does anyone know if there's any 64KB 28-pin Flash ROM?

[edwin]

I think you're going to need an EPROM burner for that. Not that I know of off-hand, I'll have a look...

should be able to find one here if it exists:
http://www.xs4all.nl/~ganswijk/chipdir/ ... ?index.htm

[Rainbow]

I think that the crashes were somehow associated with network card (3Com 3C509 EtherLink III) - it was crashing even at the slowest settings. I reinstalled Windows 95 again - and guess what - again Windows Protection Error. Removed 1MB RAM (4x256MB 30-pin) and kept only 8MB 72-pin EDO and reinstalled again - working... Haven't tried the network again.
I think that I will put 128KB Flash ROM there and wire the pins on the one end somehow - don't have EPROM burner and I want to test various BIOSes so it's not possible to get it burned anywhere.

[edwin]

256kbyte sticks are usually slow and unreliable. Especially if you have a mix-n-matched set. You want 4 identical simms from the same date and if possible the same batch. Got a whole bag of them, was able to produce three working sets of 4 so far. Might have been a critical board or something (amd386DX40).

[Rainbow]

I have 4 same pieces - from a 286 board (70ns). But I ran GoldMemory and everything was OK.