Cromemco - STDC hard Disk Controller
The STDX was a high performance,
intelligent ST506 Winchester disk controller (MFM formatted). The board came out
in 1984.
The Cromemco STDC board was an intelligent hard-disk
controller, using the ST-506 standard interface to support a wide variety of
5-1/4" Winchester drives. An STDC-controlled drive can have up to 16 heads
and 1024 cylinders. As an intelligent disk controller, the STDC needed
little attention from the host operating system. With its own Z80A
microprocessor, 64K bytes of RAM, and direct access to main memory (DMA),
the STDC allowed the host CPU to continue executing instructions during disk
read/write operations, relieving the disk I/O "bottleneck" afflicting" many
multi-user systems. System performance was further enhanced by the STDC's
four full-track data buffers. On each disk read, an entire track is
read into one of the data buffers. When subsequent sector requests are on
the same track (as is likely), the data is immediately available. If all the
buffers were full when a new read request appears, the STDC either discards
or writes back to disk the least used of the four buffers (based on
frequency of access and time since last use). In addition, the STDC could
divide a single disk drive into as many as 32 logical units. Thus, a
separate "drive" can be assigned to each user, or the apparent disk size can
be matched to a back-up medium. The STDC board was supported by the
following operating systems: Cromix-Plus, 68000 Cromix version 20.63 or
higher, and Z80 Cromix version 11.27 or higher. To run the STDC and Cromemco
WDI-II boards concurrently in the same system, the WDI-II must be modified
(refer to appendix C in the manual)
This board would be quite a project to adapt it to a CP/M system BIOS. It
was designed to be interrupt driven via a "priority interrupt cable" at the
top of the board which connected to the Cromemco FDC and perhaps other
boards. There is a good discussion about the board at the vintage-computer
forum, see
here.
The manual from Cromemco
for this board can be obtained
here.
Other Cromemco S-100
Boards
ZPU
SBC 4KRAM
16K RAM
64KZ RAM
64KZ-II
RAM
256KRAM
8KBytesaver Bytesaver-II
16KPROM
32K Bytesaver
4FDC 16FDC 64FDC
WDI WDI-II
STDC DPU
4PIO
8PIO TU-ART
D+7A I/O
Dazzler PRI
GPIB Board
XMU
XXU
Other Boards
This page was last modified
on
04/24/2014