Sigma SDC-RXV21 Floppy disk controller Q18 or Q22 compatible?

[peterbbu]

I believe that Sigma use to produce PDP11 compatible QBUS floppy disk interface cards, which unlike the DEC M8029 RXV21 also included the control and formatting controller which in the DEC product lived in the RX02 drive unit. That the SDC-RXV21 would directly drive a Shugart 800/850 series 8" floppy drive either in FM RX01 or DEC MFM RX02 compatible format.

I have found an old copy of the user guide:
https://archive.org/details/bitsavers_sigmaInfor21FloppyCtrlManFeb81_2066436

Although it says that it is a Qbus device it does not clarify if that is Q18 or Q22 compatible. Is anybody familiar with these cards.

Thanks

Peter

 

[wa2flq]

I believe that Sigma use to produce PDP11 compatible QBUS floppy disk interface cards, which unlike the DEC M8029 RXV21 also included the control and formatting controller which in the DEC product lived in the RX02 drive unit. That the SDC-RXV21 would directly drive a Shugart 800/850 series 8" floppy drive either in FM RX01 or DEC MFM RX02 compatible format.

I have found an old copy of the user guide:
https://archive.org/details/bitsavers_sigmaInfor21FloppyCtrlManFeb81_2066436

Although it says that it is a Qbus device it does not clarify if that is Q18 or Q22 compatible. Is anybody familiar with these cards.

Hi Peter,

I believe it will work in Q16, Q18 or Q22 as the they describe it as LSI 11/2 and 11/23 compatible. It won't DMA above 256KB as it only has extended address bits 16 and 17.
Check the card. It should not have BC2,BD1,BE1,BF1 wired. There may be a DY handler available that double buffers the IO for RT11 systems with more memory. Transfers to the higher addresses will be slower.

Jerry