摘要:
A circuit and process for controlling access to a digital storage device (12) is disclosed. The process involves reading a control word from a sentrol store (40) and using an address register predictor (54) for partially decoding an address field of the control word to predict the storage location to be accessed. The address field is subsequently fully decoded in a decoder (46) to determine the actual storage location to be accessed. Prior to completion of this full decoding step, an access to the predicted location in main storage (12) is initiated. In the event the actual storage location to be accessed differs from the predicted one, the memory access previously initiated is overriden and an access to the actual storage location is initiated.
摘要:
In einer Virtuell-Adressiervorrichtung zur Verwendung in kleinen Computern wird das Grundadressregister unterteilt in Segmentregister (24) und Distanzregister (22). Dadurch werden arithmetische Operationen erleichtert, weil nur der Distanzteil der virtuellen Adresse von der Recheneinheit (26) mitverarbeitet werden muss. Der Segmentteil belastet die mit nur schmalen Datenkanälen ausgerüstete ALU nicht. Dies erhöht die Leistung kleiner Rechner erheblich.
摘要:
in einem Datenverarbeitungssystem mit in Seiten unterteiltem virtuellem Speicher werden Datenseiten zwischen Hauptspeicher und Sekundärspeichern ausgetauscht. Der Austausch geschieht auf Grund der Benützung der Seiten. Häufig benützte Seiten werden im Hauptspeicher festgehalten. Zudem können Eingangs-/Ausgangsgeräte verlangen, dass bestimmte Seiten festgehalten werden. Dazu umfasst der Adressumsetzer, der virtuelle Adressen in Hauptspeicheradressen umwandelt, ein Seitenverzeichnis (24). das ein Feld zur Angabe der Seitenbenützung aufweist. Sowohl die zentrale Recheneinheit als auch die Eingangs-/Ausgangseinheiten können veranlassen, wie dieses Feld beschrieben wird.
摘要:
Zur Umwandlung virtueller Adressen in Hauptspeicheradressen in einem Computer wird eine Hash-Tabelle (20) benützt. Ein Hash-Generator (100) erzeugt eine gleichmässige Verteilung der Tabelleneinträge trotz ungleichmässiger Verteilung der virtuellen Adressen in einem System mit im Hinblick auf die Hauptspeichergrösse variabler Hash-Tabellengrösse. Ein Bitfeld innerhalb der virtuellen Adresse, das die Seitenidentifikationsbits (PID) umfasst, wird umgekehrt und mit zwei Bitgruppen eines Feldes in der virtuellen Adresse, das die Objektidentifikation umfasst, ausgerichtet. Die drei Bitgruppen werden einer exklusiv-ODER-Schaltung zugeführt. Die Ausrichtung der drei Bitgruppen und die Grösse der Hash-Tabelleneintragsadressen, die erzeugt werden, hängen von der Grösse der Hash-Tabelle ab.
摘要:
Address translation apparatus is provided for translating virtual addresses to real storage addresses and real storage addresses to virtual storage addresses. The address translation apparatus uses a page directory having a next real address and an associated virtual address ordered according to real addresses. This simplifies the manner in which the input output (I 0) handles addressing in a virtual storage computer system. When the I 0 device control mechanism needs to resolve the real I O address register, it uses the contents of that register to index into the page directory to obtain a corresponding virtual address. The corresponding virtual address is incremented and converted to a real address which is used to index into the page directory. The virtual address taken from the page directory is then compared with the virtual address which had been incremented and translated. If the two compare then the real address which had been used to access the page directory is entered into a register so as to be available as a real main storage address. In actuality it is only a partial real main storage address and is concatenated with a byte identifier portion of the main storage address which requires no translation and which was a part of the original I O real address for main storage.
摘要:
Data processing apparatus is provided with a paging facility constrained in that the number of pages of any group of pages (defined by a specific bit pattern is a first subset of virtual address bits) in residence inthe direct access data store is limited to n. The address translation apparatus included comprises two table look-up mechanisms arranged to maintain a mapping of selected virtual to real address relationships of pages in residence, the first table look-up mechanism having c / n addressable locations of n fields and the second table look-up mechanism having c single field addressable locations, when c is the maximum number of pages in residence, so that, for a filled direct access data store there is one field in each table look-up mechanism for each page in residence. Both table look-up mechanisms are addressed by the first subset of bits of a virtual address presented for translation and, in addition, the second table look-up mechanism is addressed in response to the operations of the first table look-up mechanism. Either the first or the second table look-up mechanism generates, the real page addresses appropriate to the current mapping. The first table look-up mechanism contains entries each identifying the states of a second subset of virtual address bits of pages of the associated group in residence. The second subset bits of a virtual address presented for translation are compared with all the output fields of the first table look-up mechanism using n compare circuits, outputting to the second table look-up addressing mechanism. The remaining page address bit positions of the presented virtual address are compared with the output of the second table look-up mechanism, the fields of the second table look-up mechanism containing such remaining virtual address bits appropriate to the pages in residence. If either comparator fails to detect an equality a miss is registered and the second table look-up mechanism is only exercised in relation to potential hits.