what is IDE drive size limit and system RAM limit

what is IDE drive size limit and system RAM limit

Post by Liu Davis Yu Leu » Sat, 01 Oct 1994 11:34:38

I am long reading in os2.newgroup.
It is the first time I post the News and have some input to this organization

     The ISA Bus 8 bit 16 bit IO slot which the I/O card of hard disk is
insert.In 16 bit slot (long then 8 bit but short then VESA local bus)
has about 24 address line which can accessed 16 Mbyte of system memory.
This put the limit on system RAM.Because the programe come from hard disk
by DMA or polling IO to system RAM and start executation.If the program is
within 16 Mbyte imply after 16Mbyte can use swap place or Video card ,..
other use.BUT if the IDE disk controller card is used the VESA local bus
the address line is more than 24 line,no 16 Mbyte limit.

 The limit of hard disk size is BIOS call .They use 16 bit register(AX,BX..)
 to pass parameter in disk I/O.The parameter in 16 bit register is allocate
 10 bit for cyclinder,6 bit for head/sector....This put the restriction
 of 1024 cylinder.But once os2 is booted.IT use its BIOS / not in ROM of
 mother board.It has no problem it partition after 1024 cylinder.(This is
 old stuff of 16 bit progame but not 32 bit os2)).
 This is the case for my Quantum 540 Millon byte hard disk which has 1060
 hard disk.I usen boot partition before 1024 and access other partition
 all to 1060 cyclinder.

Any correction is welcome.I get information from my memory which is base on
books and documatation in hardware with some thinking.I could be wrong
for not getting all information.



1. What is the IDE drive size limit for OS/2?


I'm planning on buying a new hard-drive. I have a VLB IDE card, it's
not the new extended IDE standard. My BIOS is an AMI version 91/92
(something). I've been told that with such a combo, DOS can handle
drives only up to 528MB and that OS/2 can do better. What is the limit
for OS/2 with a old style AT/IDE controller card?


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10. 32 MB RAM limit ?

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