2 Oct
2009
2 Oct
'09
7:13 p.m.
I wanted to let all of you know that the 2nd revision of my friend's
PC/XT IDE controller is now available. For those of you not in the
know, this is a way of using modern IDE hard drives in your 8bit PC or
XT system. Works with drives up to 137G (your O/S also has to support
it; 8.4G is way more common) and Compact Flash->IDE controllers too.
CD-ROM support is likely coming eventually, but he has to write an
entire driver that MSCDEX would talk to.
They're being sold at cost: $30 for a kit to solder your own, $40 for a
pre-built and tested card.
These are not quite the end production unit, but darn close. Works in
PC/XT clones, as well as Tandy 1000 series machines (anyone who knows
how hard it is to get an IDE drive into a Tandy will appreciate this).
They are also going to be building one that will fit into a PCjr sidecar
someday. ;)
Details are available on the last message of this forum page:
http://www.vintage-computer.com/vcforum/showthread.php?t=12359&page=109
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
11:46 p.m.
----- Original Message -----
From: "Sridhar Ayengar" <ploopster at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Saturday, October 03, 2009 2:25 AM
Subject: Re: XTIDE controller now available
Jim Leonard wrote:
Hand soldered from reading that thread, not that many boards available from
the looks of it (or parts). I think he recommended you buy the kit so you
don't complain about his soldering skills.
Sooner or later I will probably get one for my Tandy 1000 desktop when I can
figure out how to make a frame for a HD and mount one on the card (like a
hardcard).
For now the MFM drive and card I stuck into my XT clone will work.
They're being sold at cost: $30 for a kit to
solder your own, $40 for a
pre-built and tested card.
Is $40 for assembled-by-hand or wave-soldered?
Peace... Sridhar 
3 Oct
3 Oct
6:56 a.m.
Jim Leonard wrote:
I wanted to let all of you know that the 2nd revision
of my friend's
PC/XT IDE controller is now available. For those of you not in the
know, this is a way of using modern IDE hard drives in your 8bit PC or
XT system. Works with drives up to 137G (your O/S also has to support
it; 8.4G is way more common) and Compact Flash->IDE controllers too.
CD-ROM support is likely coming eventually, but he has to write an
entire driver that MSCDEX would talk to.
They're being sold at cost: $30 for a kit to solder your own, $40 for a
pre-built and tested card.
These are not quite the end production unit, but darn close. Works in
PC/XT clones, as well as Tandy 1000 series machines (anyone who knows
how hard it is to get an IDE drive into a Tandy will appreciate this).
They are also going to be building one that will fit into a PCjr sidecar
someday. ;)
Details are available on the last message of this forum page:
http://www.vintage-computer.com/vcforum/showthread.php?t=12359&page=109
Just to clarify, this is a first run of the second revision cards. They
are limited in supply, and we are probably sending them to people who
did testing with the first round. So most of them will be spoken for.
For the privilege of having an early card, you've got to do some hard
core testing. We have found very few drives that refuse to work, but
they are out there. The BIOS is still being debugged, especially with
the earlier/smaller LBA drives.
I think it's a little early to say they are being sold yet .. I'd check
back on that thread in about two months to see how testing has gone, and
to wait for the next batch of pc boards to be made up. Early samples of
this kit work already so it's not a bad bet, but it's not production
quality yet either.
(I'm intimately involved in this project - I did the trace optimization
for this last batch of cards, and helped with the early design.)
Mike
11:52 a.m.
is it asking too much to provide a list of the ic's this board takes? No problem
w/soldering in sockets, thereby alleviating the possibility of scorching any chips?
I definitely want one. Keep losing my old Acculogic card.
--- On Fri, 10/2/09, Jim Leonard <trixter at oldskool.org> wrote:
From: Jim Leonard <trixter at oldskool.org>
Subject: XTIDE controller now available
To: General at mail.mobygames.com, "On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Date: Friday, October 2, 2009, 10:13 PM
I wanted to let all of you know that
the 2nd revision of my friend's PC/XT IDE controller is now
available. For those of you not in the know, this is a
way of using modern IDE hard drives in your 8bit PC or XT
system. Works with drives up to 137G (your O/S also
has to support it; 8.4G is way more common) and Compact
Flash->IDE controllers too. CD-ROM support is likely
coming eventually, but he has to write an entire driver that
MSCDEX would talk to.
They're being sold at cost: $30 for a kit to solder your
own, $40 for a pre-built and tested card.
These are not quite the end production unit, but darn
close. Works in
PC/XT clones, as well as Tandy 1000 series machines (anyone
who knows how hard it is to get an IDE drive into a Tandy
will appreciate this). They are also going to be building
one that will fit into a PCjr sidecar someday. ;)
Details are available on the last message of this forum
page: http://www.vintage-computer.com/vcforum/showthread.php?t=12359&page=109
-- Jim Leonard (trixter at oldskool.org)
http://www.oldskool.org/
Help our electronic games project:
http://www.mobygames.com/
Or check out some trippy MindCandy at
http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
4 Oct
4 Oct
5:47 p.m.
On Fri, 2 Oct 2009, Jim Leonard wrote:
I wanted to let all of you know that the 2nd revision
of my friend's PC/XT
IDE controller is now available. For those of you not in the know, this is a
way of using modern IDE hard drives in your 8bit PC or XT system. Works with
drives up to 137G (your O/S also has to support it; 8.4G is way more common)
and Compact Flash->IDE controllers too. CD-ROM support is likely coming
eventually, but he has to write an entire driver that MSCDEX would talk to.
What am I not understanding about the need for this product? I have about
a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded. Didn't
think they were particularly rare.
Steve
--
5 Oct
5 Oct
3:25 a.m.
Quoting Steven Hirsch <snhirsch at gmail.com>:
On Fri, 2 Oct 2009, Jim Leonard wrote:
Humm, odd I've only ever seen one in the flesh, it is my perception
that they are reasonably uncommon, at least here in the UK.
Also I guess that older cards will only support drives up to 520Mb
using CHS type geometry ? And also possibly would be limited to drives
that will work in 8 bit XTA?? mode. Whereas the XTIDE has a bios that
supports LBA drives, up to 137G, mind for an XT I can't see that you'd
ever need a drive that big :)
Though asuming that the hardware on the Seagate cards was up to doing
16 bit I/O, there's no reason why the XTIDE bios couldn't be ported to
that hardware.
The other thing is this is a completely open source project, the
schematic, the bios, eveything. So whilst I don't have one of the
pre-made boards, I was able to bash the schematic into Eagle, layout a
board, and build my own, which does indeed work, may be a good way of
getting some more capacity on my 5150 and 5160 :) I'll also try it in
my Sinclair PC200 (also known as the Amstrad PC-20).
Since my controler is logically the same as the above, do you want me
to make reports of anything that does/does not work ?
Now what we really need is an MCA IDE controler........that might be a
little harder, did IBM ever release the documentation for MCA or do
they still want $$$$ fo a license. I've only ever seen one other
brand of machines that use MCA (made by Research Machines).
Cheers.
Phill.
----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.
I wanted to let all of you know that the 2nd
revision of my
friend's PC/XT IDE controller is now available. For those of you
not in the know, this is a way of using modern IDE hard drives in
your 8bit PC or XT system. Works with drives up to 137G (your O/S
also has to support it; 8.4G is way more common) and Compact
Flash->IDE controllers too. CD-ROM support is likely coming
eventually, but he has to write an entire driver that MSCDEX would
talk to.
What am I not understanding about the need for this product? I have
about a half-dozen 8-bit ISA IDE controllers, mostly Seagate
branded. Didn't think they were particularly rare. 
7:26 a.m.
On Monday 05 October 2009, afra at aurigae.demon.co.uk wrote:
Now what we really need is an MCA IDE
controler........that might be
a little harder, did IBM ever release the documentation for MCA or
do they still want $$$$ fo a license. I've only ever seen one other
brand of machines that use MCA (made by Research Machines).
NCR also made Microchannel machines, including some quite large ones
(Worldmark 5100, which at some point I had a couple of).
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
7:42 a.m.
Patrick Finnegan wrote:
On Monday 05 October 2009, afra at aurigae.demon.co.uk
wrote:
Tandy had the 4000MC too.
Peace... Sridhar
Now what we really need is an MCA IDE
controler........that might be
a little harder, did IBM ever release the documentation for MCA or
do they still want $$$$ fo a license. I've only ever seen one other
brand of machines that use MCA (made by Research Machines).
NCR also made Microchannel machines, including some quite large ones
(Worldmark 5100, which at some point I had a couple of). 
8 a.m.
On Mon, Oct 5, 2009 at 10:26 AM, Patrick Finnegan
<pat at computer-refuge.org> wrote:
On Monday 05 October 2009, afra at aurigae.demon.co.uk
wrote:
I worked with some large NCR MCA machines in the late 1990s when I was
at Lucent. Imagine a machine larger than a VAX 11/750 with four
Pentium-90 processors, multiple MCA buses and many SCSI cards on those
MCA buses and many, many disks... the scary part was it was still so
PC-compatible that it could still boot DOS and run Doom.
-ethan
Now what we really need is an MCA IDE
controler........that might be
?a little harder, did IBM ever release the documentation for MCA or
?do they still want $$$$ fo a ?license. I've only ever seen one other
?brand of machines that use MCA (made by Research Machines).
NCR also made Microchannel machines, including some quite large ones
(Worldmark 5100, which at some point I had a couple of).
5:47 a.m.
Steven Hirsch wrote:
On Fri, 2 Oct 2009, Jim Leonard wrote:
Funny, but now I know why the rest of us can't find them - you have a
personal stockpile! Most of us can't find them on eBay or other places.
This one has a BIOS that supports LBA mode drives. It was pretty funny
seeing DOS 7 boot on a PC XT 5160. The BIOS is also flashable, which is
a nice feature. (And we expect the source code to be openly available.)
There will be announcements and pointers to a proper page/site when
these things are more production ready.
Mike
I wanted to let all of you know that the 2nd
revision of my friend's
PC/XT IDE controller is now available. For those of you not in the
know, this is a way of using modern IDE hard drives in your 8bit PC or
XT system. Works with drives up to 137G (your O/S also has to support
it; 8.4G is way more common) and Compact Flash->IDE controllers too.
CD-ROM support is likely coming eventually, but he has to write an
entire driver that MSCDEX would talk to.
What am I not understanding about the need for this product? I have
about a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded.
Didn't think they were particularly rare.
Steve
6:06 a.m.
Quoting "Michael B. Brutman" <mbbrutman-cctalk at brutman.com>:
This one has a BIOS that supports LBA mode drives. It
was pretty
funny seeing DOS 7 boot on a PC XT 5160.
Is that Dos 7 as in Win 9x dos ? or as in PC-DOS 7 ?
If the former, odd that it doesn't have any 386 instructions in there
as 9x of course required a 386 or above.
Guess if you used OpenDos (or Win98 dos 7), you can use Fat32 and have
2G partitions....will try that tonight.....
Phill.
----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.
9:04 a.m.
On 4 Oct 2009 at 20:47, Steven Hirsch wrote:
What am I not understanding about the need for this
product? I have
about a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded.
Didn't think they were particularly rare.
The overwhelming majority of those old 8-bit IDE controllers worked
with XTIDE drives, which supported 8-bit data transfers.
Unfortunately, even though the ATA standard kept the 8-bit transfer
as an option for quite some time, no vendor supported it. Any IDE
drive over about 100MB is likely to support only 16-bit transfers.
As I understand the subject controller project, it latches the upper
8 bits of a 16-bit data transfer and makes it available in a
subsequent cycle.
However, one can use a CF memory card in an 8-bit IDE application, as
I understand that all CF cards support the 8-bit mode of ATA.
--Chuck
10:26 a.m.
On Oct 5, 2009, at 12:04 PM, Chuck Guzis wrote:
The overwhelming majority of those old 8-bit IDE
controllers worked
with XTIDE drives, which supported 8-bit data transfers.
Unfortunately, even though the ATA standard kept the 8-bit transfer
as an option for quite some time, no vendor supported it. Any IDE
drive over about 100MB is likely to support only 16-bit transfers.
Yes, unfortunately this is true. It's highly annoying for those
of us who like to interface IDE drives to 8-bit processors but don't
want to use CF.
As I understand the subject controller project, it
latches the upper
8 bits of a 16-bit data transfer and makes it available in a
subsequent cycle.
Ahh, very nice. Sorta like the very nice GIDE interface for Z80
systems. I've designed a similar circuit in Verilog, but haven't
tested it in real hardware yet.
However, one can use a CF memory card in an 8-bit IDE
application, as
I understand that all CF cards support the 8-bit mode of ATA.
Yes, they do. CF cards are required to implement the 8-bit
transfer mode.
-Dave
--
Dave McGuire
Port Charlotte, FL
3:18 p.m.
On Mon, 5 Oct 2009, Chuck Guzis wrote:
On 4 Oct 2009 at 20:47, Steven Hirsch wrote:
Ah. Ok, thanks all. I didn't really consider the 8/16 bit issue, but
should know better. This is a big problem when trying to find a
replacement drive for Apple II drive systems such as the Applied
Engineering Vulcan. There are only a small handful of IDE drives that
will work with them.
What am I not understanding about the need for
this product? I have
about a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded.
Didn't think they were particularly rare.
The overwhelming majority of those old 8-bit IDE controllers worked
with XTIDE drives, which supported 8-bit data transfers.
Unfortunately, even though the ATA standard kept the 8-bit transfer
as an option for quite some time, no vendor supported it. Any IDE
drive over about 100MB is likely to support only 16-bit transfers.
As I understand the subject controller project, it latches the upper
8 bits of a 16-bit data transfer and makes it available in a
subsequent cycle. However, one can use a CF memory card in an 8-bit IDE
application, as
I understand that all CF cards support the 8-bit mode of ATA.
That's an interesting fact I'll keep filed away!
Steve
--
6 Oct
6 Oct
12:05 a.m.
----- Original Message -----
From: "Steven Hirsch" <snhirsch at gmail.com>
To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org>
Sent: Monday, October 05, 2009 6:18 PM
Subject: Re: XTIDE controller now available
Ah. Ok, thanks all. I didn't really consider the
8/16 bit issue, but
should know better. This is a big problem when trying to find a
replacement drive for Apple II drive systems such as the Applied
Engineering Vulcan. There are only a small handful of IDE drives that
will work with them.
I would think an 8bit SCSI version would be cool to have as well, still
plenty of smaller SCSI drives around as well as Iomega and Syquest
removables plus tape drives.
However, one can use a CF memory card in an 8-bit
IDE application, as
I understand that all CF cards support the 8-bit mode of ATA.
That's an interesting fact I'll keep filed away!
Steve
-- 
12:30 p.m.
On Oct 6, 2009, at 3:24 PM, Fred Cisin wrote:
Quite. 16-bit ISA boards are all over the place though, like the
venerable Adaptec 1542 series. I wonder if they will work in an
"overhang" configuration in 8-bit slots; I've never tried.
-Dave
--
Dave McGuire
Port Charlotte, FL
I would think
an 8bit SCSI version would be cool to have as well,
still
plenty of smaller SCSI drives around as well as Iomega and Syquest
removables plus tape drives.
Are 8 bit SCSI cards hard to find? 
7 Oct
7 Oct
12:27 a.m.
On 10/6/09 12:30 PM, "Dave McGuire" <mcguire at neurotica.com> wrote:
IIRC, there are some that would work that way, but it was dependant on the
BIOS rom version.
Are 8 bit SCSI
cards hard to find?
Quite. 16-bit ISA boards are all over the place though, like the
venerable Adaptec 1542 series. I wonder if they will work in an
"overhang" configuration in 8-bit slots; I've never tried.
-Dave
6 Oct
6 Oct
12:36 p.m.
----- Original Message -----
From: "Fred Cisin" <cisin at xenosoft.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Tuesday, October 06, 2009 3:24 PM
Subject: Re: XTIDE controller now available
On Tue, 6 Oct 2009, Teo Zenios wrote:
Yes, especially ones with a bootable ROM that would work on an XT. I have a
few 8 bit ISA SCSI cards without ROM meant to connect CDROMs and other
devices like scanners (using drivers).
I would think an 8bit SCSI version would be cool
to have as well, still
plenty of smaller SCSI drives around as well as Iomega and Syquest
removables plus tape drives.
Are 8 bit SCSI cards hard to find?
5 Oct
5 Oct
12:39 p.m.
On 10/4/09 5:47 PM, "Steven Hirsch"
<snhirsch at gmail.com> wrote:
What am I not understanding about the need for this product? I have about
a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded. Didn't
think they were particularly rare.
Steve
From what this sounds like it is able to talk to large
capacity IDE drives,
presumedly 16-bit IDE drives. The older XT ide controllers by
seagate (that
I had) were limited to a handful of drives that could do 8-bit wide data
transfers and were very limited capacity wise.
2:10 p.m.
On Oct 5, 2009, at 3:39 PM, Geoffrey Reed wrote:
The big difference here is LBA vs. C/H/S addressing. Recall that
the IDE interface is a clone of the register-level programming
interface of the ancient WD1010 MFM hard disk controller chip family,
whose registers are 8 bits wide. There's a register for the starting
sector number (256 sectors), a register for the low byte of the
cylinder address and two bits of another register for the high part
of the cylinder address (meaning it tops out at 1024 cylinders), and
half of a register for the head number (meaning 16 heads).
1024 cylinders * 16 heads * 256 sectors * 512 bytes/sector = 2GB
I don't know where any supposed 520MB limit comes from; if someone
can enlighten me there, I'd appreciate it.
LBA (Logical Block Addressing) mode takes a large, flat linear
address space of blocks with no notion of cylinders, heads, or
sectors. It's 28 bits wide, topping out at about 137GB. IDE
interfaces take that word of bits, break it up into little pieces,
and sprinkle them across the former cylinder/head/sector registers
(and pieces of registers) in a very kludgy and inefficient way. They
take the LBA address and put the first 8 bits into the sector
register, the middle 16 bits into the cylinder number register (yes,
using it as a 16-bit register!), and the high four bits go into the
head and device select register.
Ugly, ugly, ugly.
New kludges were devised to exceed this ~137GB plateau
(obviously), but I don't know how they work offhand because I've
never designed with them.
Anyway, early BIOSs don't know how to deal with this, which is one
of the things that makes this XTIDE controller special.
-Dave
--
Dave McGuire
Port Charlotte, FL
What am I not
understanding about the need for this product? I
have about
a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded.
Didn't
think they were particularly rare.
From what this sounds like it is able to talk to large capacity IDE
drives,
presumedly 16-bit IDE drives. The older XT ide controllers by
seagate (that
I had) were limited to a handful of drives that could do 8-bit wide
data
transfers and were very limited capacity wise.
2:43 p.m.
On 5 Oct 2009 at 17:10, Dave McGuire wrote:
New kludges were devised to exceed this ~137GB
plateau
(obviously), but I don't know how they work offhand because I've
never designed with them.
Think "shadow registers"--instead of each 8-bit register in the task
file representing an 8-bit quantity, each will accept two consecutive
output or input commands and accept or return 16 bits. In other
words, each register has a flip-flop that directs I/O to either 8 bit
register. It's not pretty, but it works.
Anyway, early BIOSs don't know how to deal with
this, which is one
of the things that makes this XTIDE controller special.
Well, one can also declare a minimal conventional CHS partition from
which one boots and then install a driver to access the remainder of
the drive. Something akin to the way a drive extender works. When I
had my AT, I used some 1224 cylinder MFM drives that early BIOSes
didn't know how to handle. So I booted from a smaller partition and
then loaded my own driver. With an RLL controller, that gave me a
whopping 250MB or so.
--Chuck
3 p.m.
Dave McGuire wrote:
I don't know where any supposed 520MB limit
comes from; if someone can
enlighten me there, I'd appreciate it.
IIRC it's from the fact that most BIOSes can only deal with a 6 bit
sector number thus :
AH = 02h
AL = number of sectors to read (must be nonzero)
CH = low eight bits of cylinder number
CL = sector number 1-63 (bits 0-5)
high two bits of cylinder (bits 6-7, hard disk only)
DH = head number
DL = drive number (bit 7 set for hard disk)
ES:BX -> data buffer
Copied from Ralf Brown's Interrupt List
So 1024 cylinders x 16 Heads x 64 sectors is 512MB Later bioses I
believe used the top bits of the head number to get greater capacity.
Cheers.
Phill.
--
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !
"You can twist perceptions, but reality won't budge" -- Rush.
3:07 p.m.
On Oct 5, 2009, at 3:00 PM, Phill Harvey-Smith wrote:
Dave McGuire wrote:
There were 3 of us (I was one...I can go I'd have to think about who
the others were) at IBM that defined the mapping to ~512MB. We knew
at the time that this was a limit but we figured PCs would switch to
an LBA format before we hit the limit...we were wrong. :-)
TTFN - Guy
I don't know where any supposed 520MB limit
comes from; if someone
can enlighten me there, I'd appreciate it.
IIRC it's from the fact that most BIOSes can only deal with a 6 bit
sector number thus :
AH = 02h
AL = number of sectors to read (must be nonzero)
CH = low eight bits of cylinder number
CL = sector number 1-63 (bits 0-5)
high two bits of cylinder (bits 6-7, hard disk only)
DH = head number
DL = drive number (bit 7 set for hard disk)
ES:BX -> data buffer
6:57 p.m.
On Oct 5, 2009, at 2:10 PM, Dave McGuire wrote:
On Oct 5, 2009, at 3:39 PM, Geoffrey Reed wrote:
The big difference here is LBA vs. C/H/S addressing. Recall that
the IDE interface is a clone of the register-level programming
interface of the ancient WD1010 MFM hard disk controller chip
family, whose registers are 8 bits wide. There's a register for the
starting sector number (256 sectors), a register for the low byte of
the cylinder address and two bits of another register for the high
part of the cylinder address (meaning it tops out at 1024
cylinders), and half of a register for the head number (meaning 16
heads).
1024 cylinders * 16 heads * 256 sectors * 512 bytes/sector = 2GB
I don't know where any supposed 520MB limit comes from; if someone
can enlighten me there, I'd appreciate it.
It was originally 63 sectors. I was one of the 3 people at IBM who
came up with this scheme (because the controller we had did LBA
addressing so we needed a way to map C/H/S to LBA in a simple way).
We *knew* at the time that this was constraining but we figured that
LBA would be in place before we hit the limit. We were wrong.
TTFN - Guy
What am I
not understanding about the need for this product? I
have about
a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded.
Didn't
think they were particularly rare.
From what this sounds like it is able to talk to large capacity IDE
drives,
presumedly 16-bit IDE drives. The older XT ide controllers by
seagate (that
I had) were limited to a handful of drives that could do 8-bit wide
data
transfers and were very limited capacity wise.
3:07 p.m.
On Oct 5, 2009, at 3:39 PM, Geoffrey Reed wrote:
The big difference here is LBA vs. C/H/S addressing. Recall that
the IDE interface is a clone of the register-level programming
interface of the ancient WD1010 MFM hard disk controller chip family,
whose registers are 8 bits wide. There's a register for the starting
sector number (256 sectors), a register for the low byte of the
cylinder address and two bits of another register for the high part of
the cylinder address (meaning it tops out at 1024 cylinders), and half
of a register for the head number (meaning 16 heads).
1024 cylinders * 16 heads * 256 sectors * 512 bytes/sector = 2GB
I don't know where any supposed 520MB limit comes from; if someone
can enlighten me there, I'd appreciate it.
LBA (Logical Block Addressing) mode takes a large, flat linear
address space of blocks with no notion of cylinders, heads, or
sectors. It's 28 bits wide, topping out at about 137GB. IDE
interfaces take that word of bits, break it up into little pieces, and
sprinkle them across the former cylinder/head/sector registers (and
pieces of registers) in a very kludgy and inefficient way. They take
the LBA address and put the first 8 bits into the sector register, the
middle 16 bits into the cylinder number register (yes, using it as a
16-bit register!), and the high four bits go into the head and device
select register.
Ugly, ugly, ugly.
New kludges were devised to exceed this ~137GB plateau (obviously),
but I don't know how they work offhand because I've never designed
with them.
Anyway, early BIOSs don't know how to deal with this, which is one
of the things that makes this XTIDE controller special.
-Dave
--
Dave McGuire
Port Charlotte, FL
What am I not
understanding about the need for this product? I
have about
a half-dozen 8-bit ISA IDE controllers, mostly Seagate branded.
Didn't
think they were particularly rare.
From what this sounds like it is able to talk to large capacity IDE
drives,
presumedly 16-bit IDE drives. The older XT ide controllers by
seagate (that
I had) were limited to a handful of drives that could do 8-bit wide
data
transfers and were very limited capacity wise.
5336
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5340
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participants (15)
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afra＠aurigae.demon.co.uk -
cclist＠sydex.com -
chrism3667＠yahoo.com -
cisin＠xenosoft.com -
ethan.dicks＠gmail.com -
geoffr＠zipcon.net -
ggs17＠mac.com -
ggs＠shiresoft.com -
mbbrutman-cctalk＠brutman.com -
mcguire＠neurotica.com -
pat＠computer-refuge.org -
ploopster＠gmail.com -
snhirsch＠gmail.com -
teoz＠neo.rr.com -
trixter＠oldskool.org