Bill,

Mike's comment sounds very plausible.  I would also suggest ....

connect both drives.  Start computer and stay in RDOS ...

Using a diskette that you have booted from previoulsy ...

a;;;                      # select a disk 5.25 size

check that the a: disk select light comes on ONLY i.e. at no point B: comes
on.  If it does then some problem with drive selection

s10                     # does the seek work okay?
You hear hear diskette seeking and then the prompt comes back

rd1000 2000 1     # read into hex 1000-2000 starting at sector 1 from
current track

Now since I have a RDOS 3.12 ROM I have the TZ command.  Here is the
output.  (At RDOS level 2.5 for you I cant recall what commands exist.  Try
all of T TZ TX commands)

a;;;
A;;;s10
A;;;rd1000 2000 1
 0 10 01  0 10 09
A;;;tz

Bank 0 > 0 1 2 3 4 5 6 7 8 9 A B C D E F
         ^ ^ ^ ^ ^ ^ ^ ^ X X X X X X X X
Type (F, H) F
Drive (A-D) A
Size (L, S) S
Speed (F, S) S

Seek Tests
1 OK 2 OK 3 OK 4 OK 5 OK
6 OK 7 OK 8 OK 9 OK 0 OK
27H OK 10H OK 20H OK 0 OK 1 OK
 Restore OK
27H OK
Read/Write Tests
 Data Read OK
Write Test MAY DESTROY Data
CR=Proceed ESC=Abort ^[
A;;;

As Mike says you need to have CDOS generated for the correct diskette
sizes.  CDOSGEN came out with CDOS 2.x. It is somewhat risky but if you have
a CDOS where the B: is currenly configured for an 8" diskette you will need
to boot to A, then run CDOSGEN and regenerate a new CDOS with 2x5.25 inch A
drives.  This will overwrite your current disk, but I don't see a choice for
you!

Here is a sample session with CDOS 2.54

CDOSGEN version 02.54
Cromemco Disk Operating System Generator
Copyright (c) 1978, 1982 Cromemco Inc.

Memory size (3FFF through FFFF or 16K through 64K) <FFFF or 64K> ?

Drive A type (S = Small, L = Large) ?  s
    Seek speed (1 = 6ms, 2 = 12ms, 3 = 20ms, 4 = 30ms) <1> ? 1
    Single or Double sided <D>   ?  d
    Single or Dual density <D>   ?  d
Drive B type (S = Small, L = Large, H = Hard, N = None, E = End) ?  s
    Seek speed (1 = 6ms, 2 = 12ms, 3 = 20ms, 4 = 30ms) <1> ? 1
    Single or Double sided <D>   ?  d
    Single or Dual density <D>   ?  d
Drive C type (S = Small, L = Large, H = Hard, N = None, E = End) ?  e

Function key decoding
     (S = Standard, N = None, U = User, F = File) <S> ?  n

CDOS addresses:
  Starting address of CDOS (top of User Area)   C700
  Starting address of I/O device drivers        F944
  Last address used by CDOS                     FF41
  Top of memory for this CDOS                   FFFF
  Size of CDOS                                  38AC
  Size of boot loader (maximum = 1A00)          190B

Enter command file name <A:CDOS> -

--
marcus bennett    amou...@gmail.com majzel.blogspot.com