User`s guide

Frequently Asked Questions
B-4
Chipset Model DRAM Timing Winstone9
6
Intel 430VX AP5VM EDO 6-2-2-2 86.1
Intel 430HX AP53/AP5K EDO 5-2-2-2 86.8
Intel 430TX AP5T/AX5T EDO 5-2-2-2 87.3
Intel 430VX AP5VM/AP5V SDRAM 6-1-1-1 86.6
Intel 430TX AP5T/AX5T SDRAM 5-1-1-1 87.7
Q: Can AP5T/AX5T support 75M and 83.3MHz external CPU clock?
A: INTEL TX chipset support only 60/66MHz external (bus) clock. However, we tested the lab pilot
sample, it looks good to run 75/83.3MHz under Winstone96, perhaps INTEL BGA process is good
enough.
For the convenience of over-clocking user, we add jumper (JP5) on new version AP5T-2 and AX5T-1.
User set clock to 75/83.3MHz is taking his own risk, and is probably to have system unstable
behavior. Note that AX5T-1 supports 75MHz but without 83.3MHz, because the clock generator
reserves more pins for I2C bus. The AP5T-2 and AX5T-2 support both 75/83.3MHz
Q: What is Bus Master IDE (DMA mode)?
A: The traditional PIO (Programmable I/O) IDE requires the CPU to involve in all the activities of the IDE
access including waiting for the mechanical events. To reduce the workload of the CPU, the bus
master IDE device transfers data from/to memory without interrupting CPU, and releases CPU to
operate concurrently while data is transferring between memory and IDE device. You need the bus
master IDE driver and the bus master IDE HDD to support bus master IDE mode. Note that it is
different with master/slave mode of the IDE device connection. For more details, refer to section 2.3
"Connectors".
Q: What is the Ultra DMA/33?
A: This is the new specification to improve IDE HDD data transfer rate. Unlike traditional PIO mode,
which only uses the rising edge of IDE command signal to transfer data, the DMA/33 uses both rising
edge and falling edge. Hence, the data transfer rate is double of the PIO mode 4 or DMA mode 2.
(16.6MB/s x2 = 33MB/s).
The following table lists the transfer rate of IDE PIO and DMA modes. The IDE bus is 16-bit, which
means every transfer is two bytes.
Mode Clock per
33MHz
PCI
Clock
count
Cycle
time
Data Transfer rate
PIO mode 0 30ns 20 600ns (1/600ns) x 2byte =
3.3MB/s
PIO mode 1 30ns 13 383ns (1/383ns) x 2byte =
5.2MB/s
PIO mode 2 30ns 8 240ns (1/240ns) x 2byte =
8.3MB/s
PIO mode 3 30ns 6 180ns (1/180ns) x 2byte =
11.1MB/s
PIO mode 4 30ns 4 120ns (1/120ns) x 2byte =
16.6MB/s
DMA mode 0 30ns 16 480ns (1/480ns) x 2byte =
4.16MB/s