> On 25 Nov, Alex Buell wrote:
> > Ah yeah, the infamous COM4 bug with S3 chipsets.
> Actually it had precedence: some IBM video board (8514/A??) used that
> very address first.
>
> > Seems some fuckwit used the usual COM4 I/O port as one of its I/O
> > registers.
> It wasn't the COM4 address but something like 0xBE8 with the low 10 bits
> identical to 0x3E8, which is the COM4 base port. You'll need an
> el-cheapo serial board with 10-bit address decode only to be bitten by
> this.
please don't add confusion with wrong numbers:
IBM8514/A (and thus S3/ATI) uses 0x[4-b][26ae]e8 addresses which all will give
0x2E8 when cut off to 10 bits resulting in collision with COM4 !
0x3E8 is COM3...
> > Ahh, that particular chipset designer should have been taken out and made to use Microsoft
> > products in eternity (with a Windows 95 Beta!).
> Or the engineer at IBM who decided that only decoding the low 10 bits
> for i/o port accesses was enough for all future.
yep:(
or maybe it's the account manager who decided that there is no more money
for additional 6+ NAND inputs and thus one more chip on the board ?!
Harald
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