Re: Access more than 1MB in ISA Bus
From: Chewy509 (spamtrap_at_crayne.org)
Date: 02/27/05
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Date: Sun, 27 Feb 2005 04:37:24 +0000 (UTC)
<spamtrap@crayne.org> wrote in message...
> hi,i want to access more than 1MB size of address space in ISA Bus. It
> is the Pentium processor system with Win98 OS. The ISA Bus drive thru'
> using 82371AB(PIIX). The TOM (Top Of Memmory) register is assigned to
> 0xF2. I am not placing the ISA card in the slot insteed of probing the
> BALE, WR, RD and Address Line signal while generating cycles. The
> driver software code is generated from jungo DDK tool and linked with
> VC++ 6.0. The respective signals are getting while accessing within 1MB
> size. Can you help to access more than 1MB size momory.
>
The 82371AB southbridge internal ISA DMA controllers are based on the 82C59
DMA controller (w/ IOAPIC capability).
In addition to enabling the A20 line, you just need to program the DMA
address registers with the physical address (lower than 16MB). (The DMA
controller only handles up to 24 address lines, or 16MB).
For full details, jump over to Intel Developer Library
(http://developer.intel.com) and search for:
1. 29054801.pdf - 430TX timing charts.
2. 29055901.pdf - INTEL 430TX PCISET: 82439TX SYSTEM CONTROLLER (MTXC)
3. 29056201.pdf - 82371AB PCI-TO-ISA / IDE XCELERATOR (PIIX4)
4. 29773811.pdf - 82371AB Spec Update.
These 4 pdf's have all the info you will need.
-- Darran (aka Chewy509)...
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