Well, I've looked in the source code for Hercules/390 again. It appears that the B220 (SERVC) instruction, which is undocumented anywhere that I can find, returns the "Service Call Control Block". One of the fields in the SCCB, mapped by the IHASCCB macro in z/OS, is a byte field labelled SCCBRCC. If bit 1 is "on" (value of .1... since S/390 labels the high order bit as bit 0), then this is an IFL. Apparently z/OS, et al. check this bit early in the IPL or NIP processing and, if on, load a wait state PSW.
Note - this does not necessarily mean that there are no other differences. I would not attempt to "fake out" these licensed products by somehow messing with this bit. -- John McKown Senior Technical Specialist UICI Insurance Center Applications & Solutions Team +1.817.255.3225 > -----Original Message----- > From: Bill Stermer [mailto:[EMAIL PROTECTED] > Sent: Thursday, March 06, 2003 1:31 PM > To: [EMAIL PROTECTED] > Subject: Re: IFL speed. > > > Hi Loren, > > From the meetings we had with IBM the IFL speed will remain > at 192 mips. The basic difference between a CP engine and an > IFL engine is that the microcode for the IFL engine is > modified to only except Linux workloads not "legacy" stuff. > If there is more magic at the hardware level it was not > revealed in our meetings... > > Regards, > > Bill Stermer > EDS - City of Anaheim
