9 Dec
2003
9 Dec
'03
10:38 a.m.
Tony wrote:
I would dispute that. It's 2Mbytes for one
cylinder or thereabouts (128K
per trask, 16 heads). I don't know how many cylinders was the maximum on
ST506 drives, but certainly 1024 cylinder drives exist (and I think
getting on for double that...). Let's say 1024 cylinders.
The ST-506 interface doesn't impose any upper limit to the cylinder
count, but AFAIK, the maximum cylinder count of any real drive with
that interface was 1224, in the Maxtor XT2000 series drives (and a few
clones).
Thats 2 gigabytes of data for the emulated disk
image.
Now, 2 Gigabytes is a lot of RAM (at least to me).
I'm joining this discussion late, but why would an emulator keep more
than two cylinder's worth of data in RAM at any given time? Two cylinders
will only require 4 MB of RAM, which seems entirely reasonable.
Considering the emulator RAM (at least for the
cylinder currently being
accessed) really needs to be fast-ish static RAM, gettign 2 GB of that
is going to be unworkable...
If the RAM is organized 8 bits wide, the cycle time doesn't need to be
faster than 200 ns (assuming 25 ns sampling). That's not particularly
fast.
For a commercial design, it would probably make sense to use SDRAM, and
the slowest grade of SDRAM would be adequate.