blog:286_shootout_vlsi_vl82c311l

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blog:286_shootout_vlsi_vl82c311l [2021/03/12 09:36] – [Motherboard Data & Variants] johnblog:286_shootout_vlsi_vl82c311l [2021/04/23 14:09] (current) – [Further Testing] john
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 Other than the layout of Bank 0 of the DIP sockets, I'm not entirely convinced that there is any technical differences between the two systems. One set of data implies that the v.01 board supports up to 25MHz processors, but the chip data for the VLSI 82C311L says that the //-FC// suffixed parts are only 20MHz rated. And the //-FC// part is present on both v.0 and v.01 boards and the VLSI datasheet only lists the //-25// parts for the 386SX variant.... //so, it's anyone's guess, really//. Other than the layout of Bank 0 of the DIP sockets, I'm not entirely convinced that there is any technical differences between the two systems. One set of data implies that the v.01 board supports up to 25MHz processors, but the chip data for the VLSI 82C311L says that the //-FC// suffixed parts are only 20MHz rated. And the //-FC// part is present on both v.0 and v.01 boards and the VLSI datasheet only lists the //-25// parts for the 386SX variant.... //so, it's anyone's guess, really//.
  
 +=== BIOS ===
 +
 +BIOS from my motherboard:
 +
 +  * {{ :blog:286:biostar_mb-1220ve.zip |}}
 ===== Repairs ===== ===== Repairs =====
  
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 {{:blog:286:img20210311220029.jpg?500|}} {{:blog:286:img20210311220029.jpg?500|}}
 +
 +Next I'll need to remove the keyboard socket and repair those battery terminal tabs and any other corrosion around the area (which isn't a lot).
 +
 +//Below:// Keyboard socket replaced and battery tab solder points re-filled:
 +
 +{{:blog:286:img20210313125205.jpg?500|}}
 +
 +//Below:// DIL-14 sockets fitted in place of the original oscillator solder pads and 40MHz and 32MHz cans pushed in:
 +
 +{{:blog:286:img20210313203159.jpg?500|}} {{:blog:286:img20210313212205.jpg?500|}}
 +
 +So, did it work?
 +
 +Well.....
 +
 +{{:blog:286:img20210313211347.jpg?500|}}
 +
 +The POST diagnostic card indicates reset held high and no CLK signal :-(
 +
 +**[Update 14/03/2021]** - I swapped the processor on a chance it was faulty... 
 +
 +{{:blog:286:img20210314123150.jpg?500|}}
 +
 +The held reset light now goes out, and the CLK light stays lit. So that's an improvement. Still no error codes though.
 +
 +==== Further Testing ====
 +
 +=== Clock Signals ===
 +
 +The 14MHz oscillator which was still fitted to the board on receiving it is working; the clock is present on the output pin from the can as well as on ISA socket pin B30 (//OSC//):
 +
 +{{:blog:286:20210423_133918.png?600|}}
 +
 +There is an 8MHz clock present on ISA socket pin B20 (//CLK//):
 +
 +{{:blog:286:20210423_134011.png?600|}}
 +
 +Processor pin 31 (//CLK//) has a 9.996MHz clock:
 +
 +{{:blog:286:20210423_135456.png?600|}}
 +
 +//This doesn't seem correct//. The processor is a 20MHz unit, and is being driven, as is normal on a 286, by a standard DIL can oscillator of 2x the processor frequency (i.e. 40MHz). The definition for pin 31 is that it //"is divided by 2 internally within the processor to generate the processor clock"// (from the {{ :blog:286:amd_80286_datasheet_june_1989_.pdf|AMD 80286 datasheet}})... that would mean the processor is only at 5MHz. Unless I misunderstand the datasheet, something is drastically wrong here.
 ===== Configuration ===== ===== Configuration =====
  
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  • Last modified: 2021/03/12 09:36
  • by john