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What is a buffer board?
The buffer board, also called PuPla for a short time, separates the PAK bus from the mainboard bus. The complete address and data bus, as well as some control signals, are buffered.

Why do I need a buffer board?
There are two main reasons for a buffer board:
stability problems
  • Unpredictable (even more frequent) crashes; Simply like this, or after the PAH clock has been increased, a FRAK /? After prolonged operation or elevated ambient temperatures after the mainboard clock has been increased
  • 11 bomb crashes in programs with FPU support
  • Problems in the DMA area
Panther / 2 and network card
(only PuPla / 2)
The Panther / 2-ISA adapter contains only the ISA interrupt logic, so it can only report an attached ISA interrupt, but not trigger it on the mainboard. The new PuPla / 2 now contains the necessary circuitry to trigger a mainboard interrupt and acknowledge the triggered interrupt. The bus adapter of the Panther / 2 can unfortunately not take over everything itself, because the necessary line breaks are not present on the circuit board. If these interrupts were present, one could use the bus adapter of the Panther / 2 but no more as plug-in solution on a DIL-68000er processor, if one does not want to solder the CPU.

Technical background of the stability problems
The PuPla was developed to solve two basic problems of a PAK with the (slow) mainboard:
  • Bus load
    As the CPU of the PAH, like all processors, also has a relatively low drive power, the increased load on the address and data lines (PAK peripherals, optional FRAK /? And mainboard) has a disadvantageous effect on the heating of the chip. In addition, the CPU is exposed to higher thermal loads at higher clocks anyway. At some point, it gets too hot and the computer crashes.

  • Timing problems
    The PAK knows two basically different bus cycles:
    • Local bus cycles, which run only internally in the PAK, of which in particular the mainboard has nothing to do with, and
    • Mainboard cycles where data is read from the mainboard bus or written to the mainboard bus.
    The data and address buses are identical, however, the bus protocol is only processed via a few control signals. Therefore, mainboard cycles can cause a problem when data are read from the mainboard and a local PAH cycle follows immediately. The PAH gives "gas" immediately after the mainboard cycle (for it), in order not to lose any time. It can now happen - especially with higher PAH clocks - that the bus drivers of the (slow) motherboard are still switched on when the local PAH cycle begins. The mainboard thus interferes with the data transfer on the PAH. This may lead to a crash (usually 2-4 bombs); If the PAK cycle was an FPU instruction,
In order to deal with these two problems, the buffer board was developed. On the one hand, it relieves the CPU because it acts as an amplifier of the bus signals, on the other hand, the PuPla decouples the PAK bus completely from the mainboard bus. After a mainboard cycle, the PuPla simply closes its "gates" and so the mainboard can no longer affect the PAK bus.