Re: Old style ramdisk

Scott Laird (scott@laird.com)
Tue, 09 Jul 1996 10:22:57 -0700


In message <Pine.LNX.3.94.960708194256.5848A-100000@Cavern.NMSU.Edu>, Derrik Pa
tes writes:
>On Mon, 8 Jul 1996, Robert de Bath wrote:
>
>>
>> But, (There's always one!) I've also got this nice old 386, it's got a
>> little bit of 32bit ram and a lot more ram in ISA cards. With 1.2.13 I
>> can put the ISA card ram in as a ramdisk (with a tiny patch) and put a
>> swap file on there. Unfortunatly with 2.0.0 I can't do this 'cause the
>> ramdisk would be scattered through memory this means that the CPU is now
>> running programs from the slooow RAM, 2.0.0 ends up about 1/4 the speed
>> of 1.2.13 on an already very slow machine.
>
>Why? You take away from the memory to create a swapfile to swap pages from
>memory? I think that's a bit redundant, not to mention wasteful. That's
>like creating a RAM disk to put your WinSlows 3.1 swapfile on.

You weren't paying enough attention. He has an old ISA memory card
that he wants to use, and he wants to use the memory on it for
swapping instead of just adding it to his system's main memory pool.
This is entirely reasonable, since memory on the ISA bus can't really
keep up with a slow 286, much less a 386. As he said, using the
ISA-bus memory as normal RAM will actually slow his sysytem down
substantially. Using the slower RAM as swap size really is the best
thing for him to do, performance-wise. Less frequently used pages
will migrate to the slower memory, but can still be swapped back into
faster RAM without having to wait for a disk to seek to the right
block. It sounds odd to use a RAM disk as swap space, but it's not
always unreasonable when dealing with quirky hardware.

Scott

--
Scott A. Laird   |  "But this goes to 18,446,744,073,709,551,615"
scott@laird.com  |                - Nigel on his new 64-bit computer