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Re: EN/SC (was: NetBSD 8.0 on a Mac LC III)
On Sun, Oct 21, 2018 at 10:20:47PM -0400, David Riley wrote:
> OK, I actually ended up acquiring one from a friend who lives nearby. Opening it up, it looks like it doesn't have a CPU at all; it's a few GALs, some 74xxx buffers and registers, a DP83902 ("ST-NIC", pretty common on Mac Ethernet cards) Ethernet controller, 32K of RAM and a 27C256 EPROM. Most likely, the EPROM drives a state machine controlled through the registers and the GALs to wrap the DP83902 interface (and, probably, the RAM) in a SCSI veneer.
> That explains the performance; the data transfer speed is probably reasonable in the data blocks, but the register accesses have got to be punishing (SCSI doesn't provide for particularly speedy transaction turnaround times because it's meant to give the slowest devices time to respond).
> In any case, I'd still be interested in working on an EN/SC driver assuming it's not unreasonable to wrap an existing DP83902 driver around SCSI accesses in NetBSD. But if I'm developing something new to provide Ethernet access to older machines, it probably makes more sense to start with a higher level control strategy to minimize the transactions, so backwards compatibility doesn't really make sense here. Plus, I'd be insane to try to directly replicate the register set of the DP83902 just for compatibility with older drivers.
There are drivers for this hardware for 68k / Atari ST / MiNT
(Unix-lookalike), if this helps in any way. AFAIK these are 1:1 copies of
the Daynalink devices.
Direct download link: http://www.anodynesoftware.com/ethernet/mintn060.zip
The Daynalink also uses the 8390.
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