Hitachi 6301Y CPU Clock Speed Question

[towforce]

On investigating the "cheap" (but good enough for me - I'm not a strong player) chess computers I owned in the 1980s and 1990s, I'm finding they tended to use low-cost components like the H8 and 6301Y CPUs from Hitachi. My question is about the 6301Y.

The Radio Shack Kasparov 1850 was advertised as running at 8 MHz. However, it looks as though the CPU couldn't actually manage that speed (link).

On the Spacious Mind site (link), they say the computer had a clock speed of... "8/4 = 2 Mhz". 2 MHz makes sense - it matches the 2 MHz which the Schach Computer thread says that CPU can do - but that generates two questions:

1. What does "8/4 = 2 Mhz" even mean?

2. Were Radio Shack guilty of false advertising in claiming 8 MHz?

[Ras]

1. What does "8/4 = 2 Mhz" even mean?

Maybe it refers to some sort of waitstates? In that case, some internal operations might run at 8 MHz, but the rest doesn't, and without cache, it's mostly a 2 MHz performance.

[towforce]

1. What does "8/4 = 2 Mhz" even mean?

Maybe it refers to some sort of waitstates? In that case, some internal operations might run at 8 MHz, but the rest doesn't, and without cache, it's mostly a 2 MHz performance.

Well that's as good an explanation as I can think of.

At the time, 8 MHz was a very good speed - and surprising in a cheap computer. I think Radio Shack were not being completely honest - but it's too late to complain now.

[tmokonen]

From what I read randomly on the interwebz, 8 MHz refers to the frequency of the external crystal oscillator. The CPU (or more precisely, microcontroller) runs at a quarter of the external frequency, so it runs at 2 MHz, hence the odd 8/4=2 MHz terminology.

[towforce]

From what I read randomly on the interwebz, 8 MHz refers to the frequency of the external crystal oscillator. The CPU (or more precisely, microcontroller) runs at a quarter of the external frequency, so it runs at 2 MHz, hence the odd 8/4=2 MHz terminology.

That's a very clear explanation - thank you!

Looks as though Radio Shack were being a bit disingenuous - but I don't think the external clock would have been set to 8 MHz unless there was some benefit to doing so. Maybe some actions outside the CPU ran faster, and maybe the overall system was quicker than it would have been otherwise. OTOH, maybe the 8 MHz external clock was just as cheap and easy for them to get as a 2 MHz clock, so they went with the 8 so that they could put a big number on the box: marketing/sales types like big numbers, and it quite likely swayed some buyers. I know my brother and myself were both impressed by the number at the time.