Sharp PC-1360 find

[polbit]

(12-22-2023 03:48 AM)xerxes Wrote:  

(12-22-2023 02:07 AM)polbit Wrote:  Looking at the PC-1500 Technical Service Manual, it clearly states that the CPU gets a 1.3MHz clock. The crystal is 2.6MHz, but it's divided to drive the clock. Am I missing something here? I can't find similar information for the SC61860.

The 1.3 MHz refers to the machine cycle, mentioned on page 23 in Assembly Language Manual and on page 9 in Technical Reference Manual. The information about the SC61860 is from a German book about the assembly language of this CPU.

I think some of the facts are getting lost in translation here. To summarize:

PC-1500 uses LH5801. It has a 2.6MHz external crystal that is divided by 2 for the internal clock that runs the whole system, including the CPU. That means that the CPU speed is 1.3MHz.

Page 9 of PC-1500 Technical Reference Manual:
"These are external crystal connection pins. XL0 is the input pin and XL1 is the output pin. Clock frequency is divided by two inside the CPU. When the 2.6MHz crystal is connected the CPU operates under 1.3MHz of internal machine cycle."

Page 10 of PC-1500 Technical Reference Manual:
"Connection of the 2.6MHz crystal oscillator to XLO and XLI wil supply the clock of 1.3MHz."




PC-1360 uses SC61860. It has a 768KHz external crystal that drives the CPU without a divisor, therefore the CPU speed is 768KHz, or abour 41% slower than PC-1500 on per cycle basis. Good start to explain the performance difference without accounting for architecture.

Page 30 of PC-1350 Machine Language Reference Manual:
"The PC-1350 operates on dc 5-volt power supply and runs on the 768 KHz basic system clock. The basic system clock is generated in the CPU. The clock frequency is derived from the 768 KHz quartz crystal which is external to the CPU."