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View Full Version : AMD/Intel 9517/8237 DMA Controller issues in XT's and clones.



IBM Portable PC
November 17th, 2013, 03:28 PM
Ref. my issues with a Compaticard IV in a Tandy 1000A clone:
http://www.vintage-computer.com/vcforum/showthread.php?40133-Compaticard-IV-and-Tandy-1000A

I've been doing some reading on issues with DMA in XT's, from newsgroups:

....................beware: 8237s manufactured by AMD under license from Intel have
problems. chips marked with a date code "82" or "83" are likely
to be bad. the problem only shows up when the PC tries to use more
than one DMA channel at a time...........................

...............Steve is correct in identifying the reality of who copied who.

The original DMA controler is the AMD9517.
Intel second sourced it (under licence) and renumbered it 8237
(Intel rarely gives credit for other companies designs,
but their use of 8237 was I believe part of the agreement,
so there you are)
As the 8237 started to appear on lots of partlist for production
machines, (i.e. IBM-PC) AMD started to use Intel's number, so as not to
lose business on their own part.

All the AMD parts have always worked according to specification.
The IBM-PC design violated some of the specifications of the AMD part,
and it just happens that the Intel part is less (maybe not at all)
supseptible(sp?) to this error. AMD has since changed both parts so
that the error in the IBM design does not cause errors. I believe that
the above mentioned date codes are correct..........................
(Google links from Groups do not work. However enter "intel amd dma ibm violated" and you will find the above from a thread titled "Re: Using the DMA Controller in PCs and ATs."

Has anyone faced this issue and perhaps corrected it by replacing their DMA controller?

I've also read where people have not been able to pass POST with AMD or Intel. They then installed NEC and has no issue.

Clem

Chuck(G)
November 17th, 2013, 03:39 PM
If you want another twist, I believe that AMD copied and enhanced the Intel 8257 DMA controller and called it the 9517.

How do you like them apples? (lemons). Some Olivetti M24s/ATT 6300s are also known to have this problem.

IBM Portable PC
November 17th, 2013, 08:40 PM
I wonder if there's a DOS diagnostic tool to identify the specific issues?

IBM Portable PC
November 17th, 2013, 09:05 PM
If you want another twist, I believe that AMD copied and enhanced the Intel 8257 DMA controller and called it the 9517.

How do you like them apples? (lemons). Some Olivetti M24s/ATT 6300s are also known to have this problem.

Not sure about this, I thought the 8257 was a earlier chip?

"The original IBM PC shipped with the Intel 8257 DMA controller. This controller contained 4 independent 8-bit channels consisting of both an address register and counter. The 8257 was later replaced by the 8237 DMA controller that extended the functionality of the 8257 by providing 4 additional 16-bit channels."
http://zet.aluzina.org/index.php/8237_DMA_controller

Chuck(G)
November 17th, 2013, 10:32 PM
The quotation is full of BS. The 16 bit channels on the 5170 are due to a second 8237 being included with the address lines shifted by one bit, giving 16-bit (word) addressing. The 8257 dates from the mid 1970s. The 8237 has enhanced functionality (just compare the datasheets) and is later.

IBM Portable PC
November 18th, 2013, 12:39 AM
Well I've just rechecked and my Tandy 1000a has an NEC D8237-AC5 which I've been lead to believe is perhaps the latest version and which does work correctly.

I'll proceed to desoldering it and try an AMD and Intel for comparisons sake.......

Chuck(G)
November 18th, 2013, 07:23 AM
Don't bother yet--8237-type problems are extremely rare.

Have you tried seeing what IMD says (I think you can specify alternate DMA and IRQ/port addresses)?

IBM Portable PC
November 18th, 2013, 12:03 PM
Don't bother yet--8237-type problems are extremely rare.

Have you tried seeing what IMD says (I think you can specify alternate DMA and IRQ/port addresses)?

I've tested most combinations of IRQ and DMA, however only IRQ 4 allows me to CCFORMAT, other IRQ's either cause conflict errors when the system loads config.sys or else I receive an "overrun error" when when CCFORMAT is at track 0.

IMD?

Chuck(G)
November 18th, 2013, 01:06 PM
Dave Dunfield's ImageDisk.

IBM Portable PC
November 19th, 2013, 04:18 PM
I decided to change to a known good 360K FDD (from 1.44) and also to MSDOS 6.22 (From PCDOS 7).

No change!

I can still CCFORMAT X: /S and CHKDSK the disk on another machine with no issues.

DIR on the Compaticard drive reports:
Volume in drive G is I S (I didn't name it?!)
File not found


i.e. DIR cannot see anything.

Copying to the disk reports:
"insufficient disk space"

Being able to format /s but not DIR or copy to the drive is interesting......... actually it's more than interesting! :hammermon: