Difference between revisions of "Graduate Software"

Latest revision as of 13:44, 23 July 2024

Graduate Software was a company founded in Bristol by three people including Roger Bamkin and Simon Champion.

They provided a version of CP/M+ on 2 16KB ROMs. These were standard CPC firmware compatible ROMs.

These ROMs were available in their own ROM board expansion.

To get their CPM you were required to send them your system discs and essentially they provided a transfer service so they didn't infringe on Digital Research's copyright or distribution policy.

The ROM they provided had your address and serial number encoded on the ROM. A script has been written to update these details which can be downloaded from here.

RSX/ROM Commands

Technical

• CPM+ is stored in ROM 2 and is copied into RAM. It appears to copy the equivalent of the EMS file but with patches.
• AMSDOS ROM is required for the final part of the boot process.

Accessory/Utility ROM

Graduate's ROM based CPM allows CPM software to be installed in special Accessory ROMs.

They produced one CPM_Accessory_ROM_1 but you could buy more from them with the programs you wanted to be installed.

A utility ROM can exist in any ROM slot from 1 to 15 - these are the slots checked by the ROM.

TFM has written ROMManager which can create these accessory ROMs and he provides downloads on his website for some that he has made himself.

CormacJ has written a python script to create accessory ROMS and also extract .COM files from ROMS. You can view this at his AmstradCPCRomHacks repository

Some emulators don't support the accessory ROMs because of the non-standard format. Arnold and Caprice32 supports these.

Structure of a utility ROM

Each ROM is 16KB and has the following structure:

Each directory entry has the following structure:

Notes

1. Identification: "Graduate (C)1988". Only the first char 'G' is checked.

2. Accessory ROM name is ASCII string terminated with '$'. Graduate's Accessory ROM 1 is called "CP/M Accessory Rom 1\r\n$". You need to provide a description. At a minimum '$' on it's own is ok. The code displays the string and doesn't check if it goes past the space allocated in the ROM. Some documentation notes that this can be 32 characters long, but the Graduate Software roms will only display up to 22 characters.

3. Loading code is required. A dissassembly is shown below. The CP/M ROM executes it. Code is copied from &c070 (length &200) to &3f70 in RAM therefore copying both the loading code and the directory.

;; HL = address of directory entry
;; A = rom number
3f70 32be3f    ld      (3fbeh),a ;; ROM number store to RAM
3f73 e5        push    hl
3f74 dde1      pop     ix
3f76 2afefb    ld      hl,(0fbfeh) 
3f79 113400    ld      de,0034h
3f7c 19        add     hl,de
3f7d 118c3f    ld      de,3f8ch ;; address to call to load file from ROM
3f80 73        ld      (hl),e
3f81 23        inc     hl
3f82 72        ld      (hl),d
3f83 2afefb    ld      hl,(0fbfeh) 
3f86 111000    ld      de,0010h
3f89 0e3b      ld      c,3bh
3f8b e9        jp      (hl)

;; load file from ROM into RAM
3f8c dd6e00    ld      l,(ix+00h) ;; load address
3f8f dd6601    ld      h,(ix+01h)
3f92 dd4e02    ld      c,(ix+02h) ;; length
3f95 dd4603    ld      b,(ix+03h)
3f98 110001    ld      de,0100h   ;; load address for .COM file
3f9b cdbf3f    call    3fbfh      ;; read byte from rom
3f9e 12        ld      (de),a     ;; write to memory
3f9f 13        inc     de
3fa0 23        inc     hl
3fa1 0b        dec     bc
3fa2 79        ld      a,c
3fa3 b0        or      b
3fa4 20f5      jr      nz,009bh

3fa6 1eff      ld      e,0ffh ;; error code in H
3fa8 0e2d      ld      c,2dh  ;; F_ERRMODE - set action on hardware error
3faa cd0500    call    0005h  ;; call BDOS
3fad 3aaffb    ld      a,(0fbafh)
3fb0 5f        ld      e,a
3fb1 0e0e      ld      c,0eh ;; select disc
3fb3 cd0500    call    0005h  ;; call BDOS
3fb6 1e00      ld      e,00h
3fb8 0e2d      ld      c,2dh ;; F_ERRMODE - set action on hardware error
3fba cd0500    call    0005h ;; call BDOS
3fbd c9        ret     

3fbe 00        nop     ;; storage for ROM number

;; read byte from ROM
3fbf c5        push    bc
3fc0 3abe3f    ld      a,(3fbeh)
3fc3 4f        ld      c,a
3fc4 cdc93f    call    3fc9h
3fc7 c1        pop     bc
3fc8 c9        ret       

;; HL = address to read from ROM
;; C = rom number
;; BC' = 7F80 port number
3fc9 f3        di      
3fca c5        push    bc
3fcb d9        exx     
3fcc cb99      res     3,c   ;; enable upper rom
3fce ed49      out     (c),c
3fd0 d9        exx     
3fd1 06df      ld      b,0dfh ;; select ROM
3fd3 ed49      out     (c),c
3fd5 7e        ld      a,(hl) ;; read byte from ROM
3fd6 d9        exx     
3fd7 cbd9      set     3,c    ;; disable upper rom
3fd9 ed49      out     (c),c
3fdb d9        exx     
3fdc fb        ei      
3fdd c1        pop     bc
3fde c9        ret     

;; used?
;; BC = 7F8x with bit 3 clear. bits 1,0 are mode.
;; HL = address to read from ROM
3fdf ed49      out     (c),c ;; must enable ROM
3fe1 d9        exx     
3fe2 06df      ld      b,0dfh ;; select ROM
3fe4 ed49      out     (c),c
3fe6 7e        ld      a,(hl) ;; read from rom
3fe7 d9        exx     
3fe8 cbd9      set     3,c  ;; disable ROM again
3fea ed49      out     (c),c
3fec d9        exx     
3fed fb        ei      
3fee c1        pop     bc
3fef c9        ret   

4. Up to 16 files can be defined. Each file takes 1 entry. Unused entries are filled with &FF.

5. The accessory ROM boot program can be replaced and if needed exended by re-using some of the data area for code. In this case allocate your programs to account for this.

6. Filename is in upper case, 8 characters long, padded with spaces. '.COM' extension is assumed.

7. ROM starts at &c000. Therefore &c200 is the start of the first file.

Registered user

The name, address and serial number of the registered user is stored in ROM 1 at offset &3f00. It uses a simple encryption by XORing bytes with &4E.

Password

The password for |PASSWORD is SPLINTER This is stored in ROM 1 at offset &3f88. It uses a simple encryption by XORing bytes with &AA.

Links

• [Future OS website, home of ROM Manager and TFM's Accessory ROMs]
• Python scripts to build your own accessory roms and to patch the CPM rom to update user, address, serial and password message