US 5550962

I'll search for the specific patent number and any related litigation or CAFC docket activity.

US 5,550,962 — Verification Summary

Search scope & confidence note. I searched for the exact number 5550962 / 5,550,962 against patent databases and CAFC/Federal Circuit docket material. No CAFC 2026 docket activity, IPR/PGR, or district-court litigation naming this patent was returned. Databases indexed via search (Google Patents, Justia, FreePatentsOnline, uspto.report, CAFC scheduled-cases/opinions listings) are consistent with each other and with the authoritative full text supplied in this session. I did not directly query the USPTO Patent Center/Patent Public Search UI or PACER in this session, so the bibliographic data below rests on the supplied full text plus corroborating indexes rather than a live USPTO record pull. Where sources conflict, I flag it.

Bibliographic data

Cited prior art: US 5,321,808 A (Hewlett-Packard, "Dual process display server," 1994-06-14); non-patent literature "The X Window System" (ACM Transactions on Graphics, Vol. 5, No. 2, pp. 78–109) and "The Multi-Threaded X Server" (Proceedings, 6th Annual X Technical Conference, pp. 73–89).

Abstract (as granted)

A distributed drawing processing system including a drawing server that integratedly executes a string of drawing commands transmitted from a client program for graphics display. The client program divides the drawing command string into a block of drawing commands processable on a parallel basis and a block of drawing commands not processable on a parallel basis, and transmits the divided blocks to the drawing server. The drawing server executes the drawing command string while judging, for each divided block, whether to process it on a parallel or sequential basis.

Plain-language overview of the independent claims

Claim 1 — Client-tagged parallelism flag (broadest claim).
A drawing system with three parts: a client that sends a multi-command drawing string over a defined protocol; a drawing server that receives it and drives a display; and a communication path between them. The client side attaches a single predetermined command to the drawing command string that tells the server whether the subsequent command string should be handled in parallel or sequentially, and sends it. The server side has an "execution control determination means" that, on receipt, reads that attached command and decides parallel vs. sequential treatment accordingly. The novelty is essentially moving the parallelizability decision to the client and encoding it in-band as a control command.

Claim 7 — Explicit parallel-block bracketing (start/end pair).
Same three-part system architecture, but the client attaches a pair of commands around at least one drawing command string: a "parallel processing block start command" marking the beginning of a parallelizable string and a "parallel processing block end command" marking its end. The server, on receipt, processes the subsequent string in parallel in response to the start command and reverts to sequential processing in response to the end command. This is the concrete bracket-delimiter implementation of claim 1's general concept.

Dependency structure (for context, not independent):

• Claims 2–6 depend from claim 1 — adding a plurality of drawing threads plus a dispatcher that allocates commands to threads (2), multiple processors (3), dispatcher/threads distributed across bus-connected processors (4), client and server in the same processor (5), and client/server in different processors linked by a network (6).
• Claims 8–15 depend from claim 7 — allocating commands to threads until the parallel-block end command arrives (8), the parallel/sequential command dispatcher pair (9), multiple processors (10), bus-connected processor distribution (11), nesting an explicit sequential block between the parallel start/end pair with the whole span still run as one parallel block (12), the dispatcher pair applied to sequential sub-blocks (13), same-processor co-location (14), and network-separated processors (15).

Literal-transcription note: claim 7 as published opens "A drawing processing system compromising:" — a typo for "comprising" that appears in the granted text and in multiple reproductions of it. I have not corrected it, per instruction to interpret identifiers and text literally. Likewise, claim 8's "until said dispatch accepts said parallel processing block end command" reads as a typo for "dispatcher." These are recorded verbatim, not normalized.

Technical context

The patent addresses a known limitation of X Window System–style display servers: a server built on a multiprocessor could parallelize drawing requests coming from different clients (via per-client threads, per the Multi-Threaded X Server reference) but could not parallelize requests from a single client, because reordering drawing commands can corrupt the display. The specification's FIG. 13 example is the canonical illustration — drawing a blue square over a large red circle, where overtaking execution causes the red circle to be painted last and the blue square to disappear in the overlap zones. The invention's answer is to have the client, which is in the best position to know the drawing-order semantics of its own command stream, bracket the command stream into parallelizable and non-parallelizable regions, and let the server's dispatcher use those in-band markers to decide between the parallel command dispatcher (FIG. 10) and the sequential command dispatcher (FIG. 9) routines, with any commands outside explicit blocks defaulting to sequential treatment.

What I could not confirm

• No USPTO litigation record: I found no assignment of this patent beyond the original Hitachi assignment, no reissue/rexam, and no IPR/PGR or district-court case asserting it. Hitachi, Ltd. does appear as a defendant in unrelated 2021–2025 patent suits (e.g., FrameTech LLC, Elite Gaming Tech LLC, TurboCode LLC matters), but none of those search results tie to US 5,550,962.
• No CAFC 2026 docket entry: searches of the Federal Circuit's scheduled-cases listings and 2026 opinion summaries returned no case involving this patent number.
• Values shown on third-party aggregator sites (e.g., "Approx Value $105,000" on patentleaderboard.com) are commercial estimates, not authoritative USPTO or court data, and should not be treated as ground truth.
• The 2015 vs. 2008 expiration discrepancy noted above is a genuine conflict within the source record; I have identified which entry the maintenance-fee events support but cannot resolve it further without a direct USPTO fee-history pull.