Scor­pio News


January–March 1987, Volume 1, Issue 1

Page 30 of 63

missed out by the FDC. In fact, when sending the AIH byte, there is no clock Pulse sent berwaen dite 4 and S Similarly, when sending the OC2H byte, the Flock pulse between bite Sand 4 is mis

In single density, vardous other clock pulses are mitsed when sending control bycte’Borehe dish: nthe cable below, vhen sending « date bytey if alt E¶ clock

t nesockated vith that Byte are present then the clock can be considered Raving the value OFF Amissing clock tn any position may be represented by gera bit in the clock byte. The table also sows the values writen to the diek for the values sent to the FDC.

Byte sent Single Density Double Density 00 to Fe Write 00 to FA with Clit Weite 00 to Fe

8 Not allowed fs Write AL, preset cae

6 Not allowed Mette c2

PD Generate 2 CRC bytes Genecate 2 CRC bytes Fe to FS Write FS to FB, Clkecu, preset CRC Write FS to FB

Fe Weite FC with Clk=bu Weite Yc

FD Weite FD with CLkFF Weite =D

Fe Weite FE, Clkec7, preset CRC Weite FE

FF Weite FF with ClkepP Weite FF

Missing clock transition between bite 4 and Missing Clock transition between bite 3 and

5 i

File sizes, disk sizes and directories

+ we can at last return to CP/M and

Maving vell and truly taken a disk to ples ber wha

the questions asked at the beginning of this article. (Can anyone ret they wereu) Well, you’ll have to wade until the next episode.

ALook at MultiNet2 by P.A. Greenhalgh

Multilet Design Philosophy

The aim of Gemini’s Multinet networking system is to provide computing Facilities toa number of people for the minioum possible cost Ara very significant proportion of the cost of any system is in the mass storage and hard Copy devices, the overall cost of a multiple system installation can be dramatically reduced by allowing # number of users to share these fa

Share’ in this instance means the ability for any user to be able to of the mass storage device, but mot, in general, the sharing of the stored data

(P/M Compatibility

As Gemini Multioard systems ace all capable of cunning the CP/M operatin System, and given the amount of applications software available for that operating system, MultiNec ds designed to provide a CP/M. -compatibie Shvironment, the major difference being that the user need nov have Physical ink deives present at his Workstations but the Hultinet software refere all ise requests to a Fileserver

To achieve this, software has to be written that Looks to the applications program as though it te CP/M, but in reality this software contains no disk driver or file Mandiing routines, but instead re! foto the Fileserver that is controlling the mae etorage.

documentation is used to write software that meets the given specif closely as possible, given the major premise that there are no. physi present “Unfortunately, in practice, it is found that certain progeai Sr certain quirke’ of “undocumented features of CP/M, and so the emulatior Software hes £0 be modified in order to provide as identical an environment possible. It is chus extremely difficult, if not impossible, to achieve 100 per cent compatibility

This is an OCR’d version of the scanned page and likely contains recognition errors.

Page 30 of 63