[Info-vax] RX2800 sporadic disk I/O slowdowns

[Lawrence D'Oliveiro]

On Sat, 19 Oct 2024 21:22:08 -0400, Arne Vajhøj wrote:

> On 10/19/2024 9:04 PM, Lawrence D'Oliveiro wrote:
>
>> Here’s another question: why does a disk controller need a battery-
backed-
>> up cache? Or indeed any cache at all?
> 
> Better performance.

Think about it: the OS already has a filesystem cache in main RAM. That 
runs at main RAM speeds. Whereas the disk controller is connected through 
an interface to the CPU suitable only for disk I/O speeds. So any disk 
controller cache is on the wrong side of that interface.