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.
All RSX commands are defined in ROM 1.
- |CPMVER and |VER - This shows:
" CPM PLUS is copyright : - AMSTRAD CONSUMER ELECTRONICS PLC. & DIGITAL RESEARCH. CPM ROM by Graduate software. This rom is version 2.23 : - SERIAL NUMBER : 1232-GRAD102 OWNER : <name> "
<name> is the person who the rom was made for.
- |MYNAME shows:
Which is the same as <name> in CPMVER above.
- |OHELP or |EMSHELP - This shows:
CPM PLUS : Accessory Roms attached
It lists the names of the attached accessory ROMs.
- |EMS - starts CPM+ from ROM
- |PASSWORD - this gives a "?" prompt and asks you to enter the password.
- 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.
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.
Structure of a utility ROM
Each ROM is 16KB and has the following structure:
|&00||16||ROM identification (note 1)|
|&10||32||Extension ROM name (note 2)|
|&38||56||startup code (?) (extension ROM has &c9). This is executed.|
|&70||144||Common code to load files from ROM (note 3)|
|&100||256||Directory (note 4)|
|&200||&3e00||Data area for files. (note 5)|
Each directory entry has the following structure:
|0||8||Filename (note 6)|
|8||1||? (unknown &20)|
|9||2||address in ROM for start of data for file (note 7)|
|11||2||length in bytes of file|
|13||1||length of filename in chars (excluding padding)|
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.
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.
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.