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OLD COMPUTER
MrsR:
Hi!
I have a 486DX 33 computer bought in 1990 and still used.
The hard drive packed it in, a 2.5 gig MAXTOR IDE HD,
I haven't played around with this computer in a long time (using it for CAD work ).
When I removed the HD I found I had put the jumper in for master but also put a jumper in across pin sets 2 and 3 in effect shorting them out
what I am asking is why did I do it. I can't find any info on the net about it but there must have been a reason as it worked for 15 years
I have a 2.8 gig MAXTOR IDE HD on order and I need to know if I have to do the same to this.
It might sound a bit crazey me asking this but I haven't needed to work on any computer for years and I just forgot due to the length of time.
THANKS GUYS!!!!!
soubitos:
picandmix:
As its 1990 its probably worth a lot now we have the Meltdown and Spectre bugs that affect all post 1995 chips ! ;D
drussell:
--- Quote from: MrsR on February 11, 2018, 03:48:09 pm ---When I removed the HD I found I had put the jumper in for master but also put a jumper in across pin sets 2 and 3 in effect shorting them out
--- End quote ---
The old drive is probably an 82560? The first jumper (J50, closest to the IDE connector) controls master/slave. Jumper installed is Master/1-Drive. Open is slave. The next one, J48, is for Cable Select. For CS, you leave J50 open and short J48, the drive will automatically CS master or slave depending on cable position (when the system supports CS, of course.) The third one, J46, limits the drive to reporting only 4096 cylinders for systems that would have a BIOS hang with more than 4096. The other positions are "Factory Reserved"
The jumpers going sideways is just the way of storing unused jumpers. If you look at the board or check the resistance between the pins that the jumper is on, you'll find that they are already connected together, so storing the jumper there does nothing. You can also store a jumper with one side hanging off into nowhere, in the space where the second pin on J44 would be.
They usually (unless specified otherwise in a bulk lot buy) shipped them with a jumper on J50 for MASTER and one spare jumper in case you needed to jumper for 4096 cylinders. You never need more than the two jumpers, so they supplied two, just normally only one or none was actually required unless you needed CS or MASTER + 4096 CYL LIMIT.
--- Code: --- +---+---+---+---+---+
|J50|J48|J46|J44|J42|
+-------------------------------------+---+---+---+---+---+
| Master/Slave | | | | | |
| Only Drive in single drive system* | J | | | | |
| Master in a dual drive system* | J | | | | |
| Slave in a dual drive system | O | | | | |
+-------------------------------------+---+---+---+---+---+
| Cable Select | | | | | |
| Disabled* | | O | | | |
| Enabled | | J | | | |
+-------------------------------------+---+---+---+---+---+
| 4092 Cylinder Option | | | | | |
| Disabled* | | | O | | |
| Enabled | | | J | | |
+-------------------------------------+---+---+---+---+---+
| Factory Reserved | | | | O | |
+-------------------------------------+---+---+---+---+---+
| Factory Reserved | | | | | O |
+-------------------------------------+---+---+---+---+---+
J=Jumpered O=Open *=Default
--- End code ---
Your new one will just need to be set for MASTER. What model is the replacement?
P.S. You probably could have just replaced it with a Compact Flash card or something. :)
drussell:
--- Quote from: soubitos on February 11, 2018, 03:59:46 pm ---...
<image>
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--- End quote ---
The diagram posted by soubitos is a bit misleading, since it is missing a pin in the CS position as indicated by the purple "?" above. J46 has two pins, as correctly shown in the M / S diagrams. J44 is the only one missing a pin. (At the "top".)
In any case, the main answer to your original question, "why did I do that?" is... Because it is a convenient place to shove the extra jumper. :) It is not required. You can just omit it if you like, save it in the junk box. :)
The one jumper for MASTER is all you need.
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