[Simh] RRD40 emulation problem

[del121 at cinci.rr.com]

I recently ripped a number of CDs, including a 'vms 5.5-2 remastered' cd. 
 
This particular cd image would not mount on simh-vax running vms 6.2, giving an 
'unsupported structure level' error. However, the actual cd mounts fine on my 
uVAX 3100 M40 running vms 6.2 
 
The most obvious difference between this cd rip and the others was it's size; 
the 5.5-2 cd rip was under 200MB, all my other CD rips were over 400MB. 
 
Operationally the most obvious difference between 'inserting' the cd on the 
simhvax and my 3100 was the vms device attributes. On simh-vax VMS always 
reports 'Total Blocks 1331200' but on the 3100 it seems the hardware senses the 
actual track size; differant CDs yield differant 'Total Blocks'. 
 
On a hunch, I changed my simh device type from RRD40 to RA60 (~200MB removable 
disk pack) and attached the *same* 5.5-2 cd rip (readonly) to that. Voila! Now 
VMS happily mounts it on simh-vax. 
 
Additional info - ANA/DISK of *all* ODS2 CD rips I tested on simh-vax rrd40 
yields an error message about bitmap.sys being wrong, but NO such error with 
real cds on mv3100. 
 
Putting this all together, I conclude there is a deficiency in the RRD40 
emulation. My guess is that simh needs to determine the size of the cd rip when 
the image is attached and report actual 
total blocks when vms asks... 
 
FYI, the above is with reference to the Windows prebuilt-with-Ethernet 3.8-1 
executable. 
 
Oh yeah, side note/questions - 
 
Does the rrd40 emulation throttle the transfer rate to 150KB/S (1X CD)? Have not 
done timed tests but indirect evidence suggests that it does. This is not a 
complaint, just curious if what I sensed was actually the case. (If so, perhaps 
a 2X rrd42 could be added?) 
 
Further, if it *is* the case that the differant mass storage devices simulate 
their associated device transfer characteritics, which simulated disk is the 
fastest? RA7x, RA8x, RA9x ? 
 
Thanks...